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Star tuned magazine february 2009
TO OUR READERS                                                                IN THIS ISSUE
We lcome to StarTuned, th e
magazine for independent service
                                                                             4       ANOTHER CHANCETO BURN
tech nicians working on Mercedes-                                            Just like a blacksmith's bellows, the Mercedes-Benz AIS
Be nz veh icles. You r Me rcedes- Benz                                       "fans the flames," promoting rapid oxidat io n of pollutants
dea ler sponsors StarTuned and                                               in the exhaust stream.
provides the information coming
your way in each issue .
Mercedes-Benz wants to prese nt the
inform ation you need to know to
                                                                             10 SAFE & SECURE -
diagnose and repa ir Mercedes-Benz                                              MERCEDES-BENZ PNEUMATIC
cars accurate ly, qu ickly and the f irst                                       CENTRAL LOCKING
t ime ; text, graph ics, on-l ine and other                                 One of the convenience features used most by your
techn ica l sources comb ine to make
                                                                            customers is the central locking system. Years ago,
this possib le.
                                                                            M-B took a completely different approac h to t his by
Feature articles, derive d from
                                                                            making it pneumatic instead of electrical.
approve d company sources , focus
on bein g useful and interesti ng.
Our digest of technica l information
can help you so lve unant icipated                                           16 A QUESTION OF TIMING
prob lems qu ickly and expertly.                                             Mercedes- Benz timing chains and tensioners last
Our list of Me rce des-Benz dealers
                                                                             and last. But, given the tremendous numbe r of
can help you f ind Genuine
                                                                             miles people put on these vehicles, they will need
Merced es-Benz Parts.
                                                                             attention sooner or later.
We wa nt StarTuned to be both
he lpfu l and informative, so please let
us know just what kinds of features
and other diagnostic services you'd                                         26 THE STRAIGHT & NARROW
like to see in it. We'l l continue to                                       When evaluating chassis integrity after collis ion damage
bring you selected service bu ll etins                                      you need to take the extra steps to verify st raightness.
from Me rcedes-Benz and artic les                                           The inherent value of a Mercedes-Benz veh icle definitely
covering the different systems on                                           makes these extra steps worthwhile.
these vehicles.
Send your suggestions, questions
or comments to us at:
StarTuned
                                                                             31 GENUINE MERCEDES-BENZ
One Mercedes Drive                                                              PARTS ... NEARBY
Mo ntvale, New Jersey 07645                                                 Wherever you are in the United States, there's a nearby
Phone: 1 8002256 262 , ext. 7112                                            source of genuine factory parts for your customers'
e-ma il : StarTuned@mbusa.com                                               Mercedes-Benz veh icles.

StarTuned is a quarterly publication of Mercedes-Benz USA, LLC (" MBU SA"). N o pa r t o f this news lette r may be rep rodu ced without the express written permission of
MBUSA. Ed i to r ia I and Circulation Offices: 598 Pine Po int Dri ve . Ak ron. Ohio 44333. Caution: Vehicle servicing performed by untrained persons could re sui tin se ri ous
injur y to t h ose pe r so ns or others. Informatio n contained in this news letter is intended fo r use by tra ined, pro fess iona l auto repa i r technic i ans ONLY. Th is
informat ion is prov i ded to i n form these tec hnic i ans o f co ndi t i ons wh i ch m ay occur in some ve hi c le s or to prov ide inform a t io n wh i ch cou ld assist
th em in prope r servic ing of th ese veh i c l es. Proper ly train ed tech nician s have til e equ i pm en t , t oo ls, safe t y ins truc tio ns, and k now-how to perfo r m repairs
correct ly and safely . If a cond iti on is desc ri be d, DO NOT ass um e tha t a topi c covered in these pages automa t ic all y ap pli es to yo ur ve hi c le or that you r veh icle has
th at condition. StarTuned is a registered trademark of MBUSA.
STARTUNED
Information for the Independent Mercedes- Benz Service Professional
February 2009 U.s. $6.00 € 1 2.50   Volume 9 Number I


Group Publisher              Contributing Editor    MBUSA Technica l                 Production Manager
Christoph er M. Ayers, Jr.   Chip Keen              Content Advisor                  Devon Ayers
cayers@cmacomm.com           ckeen@cmacomm .com     Donald Rotolo                    dayers@cmacomm.com
                                                    Donald.Rotolo@mbusa.com
Senior Project Director      Contributing Editor                                     Circulation Manager
Tamra Ayers                  Ke rry Jonsson         MBUSA Project Manager            Joann Turner
tayers@c macomm.com          kjonnson@cmacomm.com   Stephen Langelotti               j turner@cmacomm .com
                                                    Stephen .Langelotti@mbusa .com
Editorial Director           Contributing Editor                                     List Consultant
Bob Freudenberger            T Nash
                              om                    Art Director                     NFocus
bfreud@cmacomm .com          tnash@cmacomm.com      Jef Sturm
                                                    jsturm@cmacomm.com
FEATURE ARTICLE
Just like a blacksmith's bellows, the
Mercedes-Benz AIS "fans the flames,"
promoting rapid oxidation of pollutants
in the exhaust stream
   Whether you believe technological            the fire in the old two-way catalytic
developments are motivated by tightening        converter. In th e early '80s when the
government regulations, or by the desire to     three-way cat became popular, the air
add va lue for new-car buyers, there's no       was piped into the cat downstream of the
doubt that they are coming along at an          redu ction section after the engine warmed
ever-increasing rate. Secondary air injection   up so that it wouldn't interfere with the
systems, however, have a long history -         reaction that broke down NOx, yet was
they've been fighting air pollution since the   available for the oxidation section.
1970s. Of course, they're way different today
from what they were then .                      Seltless
   Originally, a belt-drive n pump forced air
in to the exhaust manifold to help oxidize        A modern Mercedes-Ben z secondary AIS
escaping HC and CO. This was taken one          (Air Injection System) does away with that
step further when that air was used to fee d    energy-wasting and space-hogging belt in




                                                                  On VB engines, the
                                                                  secondary air system is
                                                                  easy to test. Everything
                                                                  is right in front of you.
                                                                  Here we have the air
                                                                  pump, shut-off valves
                                                                  and switch-over solenoid,
                                                                  all nicely accessible.




                                                                                             StarTuned 05
SECONDARY AIR INJECTION SYSTEMS

                                             favor of an electrically-driven pump . Th is also
                                             allows much more precise control of airfl ow,
                                             which is necessary as emissions regulations
                                             continue to become stricter on both federal and
                                             state levels, and as the quest fo r improved fuel
                                             efficiency continues.
                                                The secondary air pump motor is only activat-
                                             ed when the engine is relatively co ld - below 60
                                             deg. F. It is only commanded on fo r up to two
                                             and a half minutes. This is sufficient to warm up
                                             the catalytic converters. The pump receives its
                                             power supply from the secondary air pump relay,
                                             which is operated by the ME contro l unit. The
                                             system is also activated during closed-loop
                                             operation, but on ly to test the system's abilit y to
                                             pump air into the exhaust - the ME contro l unit
                                             looks at the reaction of the 02 sensors.
                                                There is one exception to th is rule. Early 111
                                             Eva engines (four-cylinder supercharged) do not
                                             use an electric pump. The ME control unit uses
  On supercharged models, the                the supercharger to genera te t he necessary pres-
                                             sure/flow of fresh air to the exhaust. On models
  compressor generates the air that is       with an electronically-controlled "compresso r"
  supplied to the exhaust ports through      clutch, the clutch is activated at engine tempera-
                                             tures below 60 deg. F., and can be kept engaged
  this shut-off valve. Notice the solenoid
                                             for about two and one half mi nutes . On later 111
  mounted nearby that supplies vacuum        engines, there is no supercharger clutch, so the
  to open the shut-off valve.                compressor is always spinning. The recirculation
                                             flap is held closed to allow the compressor to
                                             make the relatively sma ll amount of air pres-
                                             sure/flow that the exhaust air inject ion requi res.




                                             When the secondary air pump
                                             motor is activated cold, or you cause
                                             it to activate, you can measure the
                                             amp draw of the pump. As you can
                                             see here, around 26 amps should
                                             be your reading with a normal
                                             motor. If it is lower; the pump por-
                                             tion is probably worn. If the amp
                                             reading is too high (fused 40 amps)
                                             the motor may be seizing up.


06 StarTuned
Your paid subscription to
                                                                        www.startekinfo.com allows
                                                                        you to pull up the wiring
                                                                        diagram for the engine
                                                                        management system. Look
                                                                        at components K17 (relay)
                                                                        and MJJ (air pump motor),
                                                                        and you should be able to
                                                                        come up with a diagnostic
                                                                        plan to activate the relay
                                                                        and test the air pump.


      Shut-off valve                                        stream, the 02 sensors register the high oxygen
                                                            content in the fresh air and this signal causes the
        From the pump, the air is directed to a shut-off    ME control unit to assume that the engine is run-
      valve. This valve is vacuum-controlled, and is nor-   ning lean . The ME's adaptation programming
      mally cl osed to block exhaust gases from reach-      tries to compensate for the lean condition by
      ing the pump when the system is not energized.        adding fuel. The ME looks for a lambda value
      On four- and six-cylinder engines, there is only      change of 25%. If the change is less than 25%,
      one shut-off valve, but there are two on eight-       the control unit determines that there is low flow
      and twelve-cylinder models. When the system is        of the secondary air injection system and flags a
      active, a switch-over solenoid supplies vacuum to     code of P041O, or one of its variants. This could
     the shut-off valve(s) . This solenoid is ground-con-   be caused by no voltage to the secondary air
     trolled by the ME. Remember, with engine tem-          pump, or a weak pump. An inoperable switch-
      perature below 60 deg. F. the switch-over sole-       over solenoid or a stuck shut-off valve can also
      noid is grounded, which supplies vacuum to the        cause codes. If all these components are func-
     shut-off valves, opening them. Air is then sup-        tioning properly, you may still have the problem
     plied to the secondary air passages cast into the      of blocked passages in the cylinder heads. How
     cylinder head and exits into the exhaust ports.        are you going to determine what's at fault?
     This oxygen rich air mixes at the earliest point
     with the hottest exhaust gases and promotes            Codes and testing
     continued combustion. The heat generated from
     this process in the exhaust manifold heats up the        Since problems in the secondary air system
     catalytic converter fast and therefore reduces         usually do not cause drivability symptoms, you
     overall emissions quickly.                             will probably be diagnosing a code in the P0410
:JIII._ Being an emissions control system, AIS must         range. The customer will more than likely bring in
     have self-diagnostic capabilities. So, has its own     the vehicle with a CEl (Check Engine light) or
     monitor. Both the secondary air pump and the           Mil (Malfunction Indicator lamp) on. You are
     switch-over solenoid are activated during a nor-       going to have to test components, and you are
     mal drive cycle. Once the pump supplies fresh air      going to have to start somewhere. Having a
     through t he shut-off valve into the exhaust           Compact III or Basic is a tremendous help when


                                                                                                      StarTuned 07
SECONDARY AIR INJECTION
           it comes to diagnosing any prob lem with a
           Mercedes- Benz system, but we believe you
           need to back up any scan tool diagnostics with
           direct component testing for verifica t ion.
--..,.,,--     Testing the pump is fa irly simple. Remove the
           engine covers and provide power to the motor
           connecto r. You shou ld hear a loud whirring
           noise. Whenever you compress air, even though
           fi ltered, you are going to condense water, espe-
           cia lly in high-humidity climate s. Thi s moisture
           can get into the electrica l portion of the motor
           and ca use failures . Th is is why the motor is
           usually mounted on the engin e. The heat
           shou ld cause any bu ilt-up moisture to evapo-
           rate. The current draw of a good pump w ill be
           25 to 26 amps. Any lower and you're probably
           not pumping much air, and anything higher and
                                                                     The switch-over solenoid receives
           the motor is sta rting to se ize .                        manifold vacuum, and, when
:::!I._        If you are lu cky enough to have the vehic le
                                                                     energized, directs this vacuum to the
           overn ight, you can ve rify the air pump relay
           operation. The pump power supp ly wire should             shut-off valve. You can energize this
           see battery vo ltage within a few seconds of a            solenoid through the SDS software in
           co ld start. This vo ltage can remain on for up to
           150 seconds. If vo ltage is low or not there at           your Compact III, or simply ground it
           al l, yo u will need to locate the secondary air          with a test light and check for vacuum
           pump relay. You can manua lly ground the relay
           and see that volt age is supp li ed to the pump.          at the shut-off valve.
           With a pa id subscription to
           www.starteki nfo.com. you can retrieve a wirin g
           diagra m for the veh icle and component loca-               What does the 02 sensor say?
           t ion usi ng Star Finder. As mentioned earli er, the
           relay is contro ll ed by th e ME. With your                    To test the shut-off va lve, you can app ly
           Compact III or Basic, you can command the                   vacuum to it with a hand-he ld vac uum pump - it
           re lay on even if the engine is already warmed              shou ld hold. How wi ll you verify that it is actually
           up. Or, you can apply a test li ght to the ground           open? You cou ld remove and phys ica ll y watch fo r
           contro l of the relay. You shou ld hear the relay           movement, but there are better methods. You
           click and the pump run . Th e current draw of               can app ly vacuum to the va lve and watch the
           the relay is around 100mA. If th is is not the              front (upstream) 02 senso r signa l. It shou ld drop
           case, ve rify that you have vo ltage to both the            to 0 mV with the secondary air pump command-
           control coil and switched circuit of the relay.             ed on and vacuum appl ied to the shut-off va lve.
- - --          If everything so far is in work in g order, you        If the 02 sensor reads a lean condition, but does
            will want to test the switc h-over so lenoid and           not drop to zero, you can assume that the
            shut-off va lves. The soleno id va lve is contro ll ed     shut-off va lve is work ing, but there may be an
            by t he ME, so the Compact III or Basic scan               additiona l prob lem. Th e ME contro l unit looks for
            too l will be ab le to activate the so lenoid, or you      the Lambda (fuel trim) reading to compe nsate for
            can once again manually ground the so lenoid               the fa lse lean cond ition by add ing 25% more f uel.
            with a grounded test light whi le the engine is            If the secondary air passages are clogged or
            runn ing. Yo u should measure manifold vacuum              restricted in the cylind er head, the 02 sensor wi ll
            at the shut-off va lves.                                   not see the false lea n cond it ion and as a result


           08 StarTuned
You can apply vacuum to
                                                                                                    the shut-off valve and see if
                                                                                                    it holds. This should also open
                                                                                                    the valve. If you remove the
                                                                                                    hose from the air pump motor
                                                                                                    you should fee l exhaust
                                                                                                    coming out of the valve while
                                                                                                    the engine is running.


' - -1111111                                      -lolxI                      II6lilil          the ME wi ll set a code for low secondary air flow.
Vehicle
              ~-   ...                                     ontrol unit   I                      This is one of the more difficult problems to
IModel ! MEl IA c t iva t ions
~'
         R    AIR pump                                                                          repair. Short of removing the cylinder head for a
m-       AIR pump


~
~
~
t99
              025 voltage
              r ig h t
              Ie f t
                                        .mv
                                         S   tOFF


                                             mV
                                                     I                                          thorough cleaning, you wi ll have to find a way to
                                                                                                clear the carbon bu ilt-up in the intake passages.
                                                                                         C:: =. _ With a little luck and some good chemicals you
 ~
- 7t-
1
                         025 vol tage drops
                         below 40 mV wi t hi n
                                                           r----                                may be able to clear the passages in the cylinder
~
 170 ( 38-p              ~~ynds?Fl
                          N <ltI FF
                                                           I--
                                                           -             -
                                                                                  -
                                                                                  -
                                                                                                head without removal. Remove the shut-off
                                    ?
                                                                                                va lves and pour a reasonab le amount of cleaning
                                                                                                solution down the ports . You can remove the
                                                                                                exhau st manifolds and plug off the secondary air
                                                                                                ports, but this is not necessary. You will have to
!J ~
~ fWiiil
                          ~               1J                                 !J
                                                                             .                  let the cleaning solution sit over night. It also
                                                                                                make take a few appl ications before the
                                                                                                passages are clear, but after softening up the
  Using your Compact III or Basic                                                               carbo n in the ports, apply shop air pressure to
                                                                                                the shut-off va lve exhaust ports and you shou ld
  scan tool, you can perform a                                                                  be able to open up the passages. If not, the
  secondary air ~ow test while                                                                  cylinder head wi ll need to be removed for better
                                                                                                access to the ports.
  the engine is running. Even on
  older vehicles such as this I 29                                                              You   can do it
  chassis, you can use the HHT
                                                                                                  Although pol lution contro l devices add com-
  software to command the                                                                       plexity to an engine's air/fuel/ignition manage-
  secondary air system on and                                                                   ment system, the above shou ld serve to illustrate
                                                                                                that as long as you understand how any part of
  see the reaction of the 0 2                                                                   that system works, you can follow a logica l
  sensors.                                                                                      process to come up with an accurate diagnosis .
                                                                                                That capabi lity wil l make yo u popular among you r
                                                                                                custo mers. One more thing: Think about adding
                                                                                                the pa ssages of the AIS to any ca rbon-cleaning
                                                                                                service you offer.



                                                                                                                                          StarTuned 09
FEATURE ARTICLE




                      Mercedes- Benz vehic les have always had some uni que features . Along
                    with reliability, longevity, safety and performance, they've hel ped make
                    these engin eerin g masterpieces some of the most sought-after ve hicl es in
                    th e world.
                       One unique feature introd uced in the 1960s is the pneumatic centra l lock-
                    ing system, wh ich, as the name imp lies, does not use the electro-mechanical
                    actuators othe r manufacturers emp loy. In stead, it uses a co mbination of vac-
                    uum and pressure to move the door lock actuators quietly and dependably. It
                    has with stood the test of t im e and co nt inu es to this very day. As with any
                    unique system, however, there is a certa in leve l of fa milia rity that is neces-
                    sary in order to diagnose and repair the system.


10 StarTuned
Histo rical Perspective
   Th e ea rliest reference we can find to pneumatic centra l locking in
Mercedes-Benz arc hives is from over 40 years ago. Back then, engin e
intake manifold vacuum stored in tanks did the lock in g, but the system
soon evo lved to use comb ination vac uum /press ure pumps to supp ly the
force needed. From 1983 onward, the change from vacuum to
pressure is accomplished by electrically reversing the rotation of the motor
- negative contro l vo ltage for vacuum, pos itive for pressure. Previously,
this had been done by means of a switching va lve . A typ ica l pump, by the
way, shou ld produce .5 Bar (7 psi) with in two or three seco nd s.


                                                                               StarTuned I I
PNEUMATIC DOOR LOCl( S


       With a paid subscription to
          www.startekinfo.com. you
                have access to W/S
                                                           ~1IlJa.otP"''''.
                                                                                                                                                                                  Doe ,no QTIIO.2O+OQOS.01.       PtIgI t   ot '


            (Workshop Information                      I o".m'"' L_ _
          System), which will allow
                  you to pull up on
          operational schematic of
        the central locking system.
                 This shows all the                                                                                                                                                              PBO,1(J.204 1·09

           components involved in                          AV 1
                                                           As/1
                                                           A2dl1
                                                                2    Top 199( wmdON antenna ampliflof
                                                                     Remote control key
                                                                     Lell fronl door fR receiver
                                                                                                          N 1043
                                                                                                          N6911
                                                                                                          N6912
                                                                                                                   Reaf SAM control module
                                                                                                                   Loti front door con/rol module
                                                                                                                   Right lront door control module
                                                                                                                                                           fV13

                                                                                                                                                           SOOIf
                                                                                                                                                                   Electronic ignition switch con /rol
                                                                                                                                                                   module
                                                                                                                                                                   Left fron l door lock SWitch (CA               8
                                                                                                                                                                   <D (valid for Jeft-hand steer/no)
       commanding the PSE mod-                         I   A26f2     Right front door fR receiver         N10      Overfle8d con/rol panel control
                                                                                                                                                                                                                    CD
                                                           A37       PSE control module (combined)                 module
                                                                                                                                   .                       581/1   Rk,Jht front door lock SWitch (CA
                                                                                                                                                                   /._ /"" ... . . _ ..... ,.. .......>-...1_ •



      ule to lock/unlock the doors.                     SIIHcIH ~OO SE CI65OO1C L 600                                      '.m 211),175     EnoineM "ueo




      Press ure in the system is relieved in 15 to 20 seconds                                        one quick tip, however: If th e veh icle has an EDW
      after the pump stops . If there's a heavy leak, the                                            alarm system, you can disconnect the intermediate
      electronics that contro l it switch it off in 2 5 to 60                                        plug of the EDW cab le harness from the connector
      seconds.                                                                                       (M14/1x2, or M14/2x2) and connect the central
         Since about 1986, most M-B cars have had what's                                             locking cab le harness directly to the supp ly pump. If
      called the "multi-point" (also called "3- Point") system.                                      ce ntral locking works okay now, it's time to delve
      If you 're not sure what you're dealing with, go to the                                        into the EDW.
      passenger's door and unlock. If all the other doors do
      the same, yo u' ve got multi-point. If not, eith er you're                                     PSE Modern System Operation
      working on a car with the old er single-point syste m
      (which unlocks on ly from the driver's door), or there's                                          At the heart of the centra l locking system is the
      a problem. But since yo u' ve been presented with a                                            pneumatic control unit, which is in total control of
      compla int about this feature, you may be unable to                                            the pneumatic portion of the system, and the vac u-
      get any action out of it whatsoever. That means                                                um/pressure pump is mounted in side it. It also
      you've got to dig deeper.                                                                      plays a role in operating the Clos ing Ass ist (CA).
         Around 1990, IRCL appeared, which meant the                                                 The PSE module is usually mounted under the rear
      locking function cou ld be operated by either the door                                         seat on sedans and in the trunk on smaller coupes.
      lock switches, or an infra-red remote. The PSE                                                 As the PSE module evolved, so have its inputs -
      (Pneumatic System Equipment) modu le received all of
      the in puts and outputs to command the door locks.
      By '96, tne door switcn contacts were elimin ated, and
                                                                                   C::_.             more than just direct switch inputs command it.
                                                                                                        Nylon hose is used to connect all of these com-
                                                                                                     ponents and route vac uum and pressure through-
      the RCL (Radio Central Locking) module took control.                                           out the centra l locking and clos i ng assist systems.
l:1li._   The integration of centra l locking with anti-theft and                                    These hoses direct vacuum/pressure from the PSE
                                                                                                     modu le to the individual door lock actuators. They
       remote contro l systems evolved as the years went by,
       and is quite complex with dozens of variations. Since                                         have a single port on one side of a diaphragm.
       a magazine article cannot possibly provide all the                                            Supplying vacuum to it moves the actuator to
       details, you will definitely need www.startekinfo.com.                                        either the lock or unlock position . Supplying pres-
       and WIS for specific information on the model at                                              sure to the same port does the opposite. As you
       hand. Here, we will cover the basic principles and sig-                                       can imagine, this needs to be a "closed" system .
       nificant addit ion s to give you a roadmap . We 'll offer                                     Any leaks can cause malfun ction.



      12 StarTuned
I~   hF8np"    ii   HHlWIN                                              I!II:lEl                     ...   C:'I"     ~
                                                                                                                            Your Compact III or basic
    Vehicle                                                                           ontrol unit   I
                                                                                                                            scan tool can access
    rcurrent           PSE Functions
                                                                                                                            data that includes version
    IFilter stal I---::---:!C:-o-n~t-r-o-:-l-m-o-:-d-u':"'"1e-v-e-r-s""'i'-o-n--l
                          DTC memory
                          Actual Values                                                0245458532               - ./-
                                                                                                                            identification, diagnostic
                            Version          coding
                                                                                                                            trouble codes, actual values,
                                                                                                                            actuations and coding.
                                                                                                                            This is an excellent way
                                   diagnosis
                                            <lIt~
                                                                                                                            to check multiple switch
                                                                                                                            inputs, even those from
                                                                                                                            other control units, without
                                                                                                                            having to test each
                                                                                                                            individual circuit.

---"_ _ As mentioned, from the early '90s the PSE module
         received all of the inputs and outputs to command
         the door locks . Starting with the early versions, one
         of the basic commands to be seen by the PSE mod-
         ule are those from the left and right door switches,
         which are within the pneumatic actuators. Rotating
         the key in the door lock or actuating the lock button
         atop the door signa ls the PSE. There is one switch
         conta ct for the lock command and another for
         unlock, and they are wired together with the trunk
         lock switch. Any of these inputs can switch the signal
         voltage of the PSE module to ground. When the mod-
         ule se es t his, it wi ll eith er lock or unlock the doors .
         There are other switched inputs, but most of them
         are for determining door and trunk latch positions .
...-- - - Later PSE modules have self-diagnostic capabi lit ies .
         It can store codes and data even with systems as far
         back as HHT, which is incorporated into the Compact
         III SDS system. You can see multiple switched inputs
         at a glance. You can monitor the lock and un lock
         command switches in each individual latch, trunk                                               By monitoring the SN I and SN2 signals,
         tumbler, trunk lid position, individual door position
         and inte rior CL switches. Since there can be varia-                                           you can evaluate the command to the
         t ions dep ending on veh icle options, the PSE module                                          PSE module to both lock and unlock the
         needs to be version coded if replaced. Some vehicles
         have CA (Closing Assist), others have RCL (Remote                                              doors. You do not need to use an oscillo-
         Central Locking) or CF (Comfort Lock system)                                                   scope to monitor these signals. A DMM
         options.
C _ _ If the vehicle is equipped with Infra-Red (IR) remote                                             will work fine. You are looking for a I 2V
           controls, there are some differences in the way the                                          signal on each of these wires.

                                                                                                                                                 StarTuned 13
PNEUMATIC DOOR LOCKS


      system works. The basic door lock/ unl ock switch              Testing the System
      signa ls are supplemented with door switch com-
      mands referred to as SN1 and SN2 signa ls, wh ich
                                                                  C=-_  If the pneumatic central lock ing system is not
                                                                     function in g properly, one of the first steps is to find
      originate in the Remote Centra l Lock ing (RCL) mod-
                                                                     out if there is a problem with the pneumatic system -
      ule. Either can co mmand the doors to lock/ unlo ck.
                                                                     the vacuum/pressure pump, nylon lines, or any of the
      By '96, the door switch contacts were elimin ated.
                                                                     three to five actuators - such as a leak, bind ing, or
      The RCL has taken ove r for these manual contro ls.
                                                                     seizing. This can be done fairl y easily at the PSE
      This means the RCL is in control of the door locks
                                                                     con trol module . You will notice a single large line
      and the signa Is to the PSE module have to be tested
      in order to determine if the PS E is work in g. These          com ing out of the module and feeding one of two
      SN 1 and SN2 signa ls are also passed on to the ATA
      (Anti-Theft Alarm) system to confirm that an accept-
      able remote opened the doors before the engin e is
      all owed to sta rt (as of '98 w ith SmarKey, engi ne
      start ing is a sepe rate function fro m CL and ATA).
      Knowing th is can be helpful in diagnosing the PSE
      function if it is not work ing. Open the driver's side
      window, close the hood, trunk and all the doors.
      All ow the vehicle 's alarm to arm itself. Then, use the
      remote to open the doors. If the doors do not
      unlock, reach in thro ugh the win dow and try to start
      the engine. If it starts, you know the RCL signal
      made it to the ATA mod ule and therefore must have
      made it to the PSE mod ule. Th e module sho uld have
      unl ocked t he doors. If the engin e does not start, you
      may have a prob lem with the RCL system. Monitor
      the vo ltages on SN 1 and SN2 and see if th e 12V sig-
      nals get pulled to ground for eith er t he lock or
      unlock command.
c:z_ _    A later evolution of the system is the Conven ience
      Feature (C F). This integrated the operation of many
      body contro ls into one contro l unit, in cluding power       Looking at these signals on a dual
      windows, power door locks and power slidin g pop-up
      roof. The CF contro l unit directly contro ls the win-        trace scope allows you to see the lock
      dows. Door locks are sti ll controll ed by t he PSE unit,     command (upper trace) and unlock
      but it receives commands from either the door
      switches or t he CF contro l unit. After '96 when the         command (lower trace). As you can see,
      door switches were eliminated, the Drive                      the I 2 V signal gets pulled to ground
      Authorization System (DAS) radio frequency/Infrared
      (IR) contro l module took over command ing the PSE            when the door locks are actuated, in
       unit to operate the power door locks.                        this case by the RCL unit as the remote
CII_ _ Another feature close ly related to the PSE system
       is Closing Assist (CA), wh ich uses its own separate         button is pushed to open and close the
       co ntrol unit that is referred to as the CA supp ly          doors. The signals are there, but the
       pump. It is only used for lock in g, not for unlocking.
       The goal is to continue to close the door all the way        pneumatic pump did not turn on.
       after latc h con tacts the door j amb. A door micro-         At this point check for powers and
       switch ind icates whe n the door is alm ost closed and
       th is signals the CA system to supp ly vac u-                grounds to the PSE unit. If they are
       um/pressure to the CA actuators in the door latch            good, replace the PSE module.
       assemb lies .

         14 StarTuned
Star tuned magazine february 2009
FEATURE ARTICLE




   Mercedes-Benz timing chains and
   tensioners lost and lost. But, given the
   tremendous number of miles people put
   on these vehicles, they will need attention
   sooner or later
1 Stal-Tuned
 6
tion of Timing
   In order for a four-cycle engine to work,                 marginal, and making replacement at regular
there must be precise coordination among the                 intervals necessary. On the other hand, in a
intake, compression, power and exhaust strokes .             properly-maintained vehicle timing chains and
Advances in engine technology have helped                    related hardware can last well over 200,000
increase performance throughout the rpm range.               miles. Eventually, however, wear will reach the
Variab le intake manifold runners optimize air               point where diagnosis and replacement wi ll be
inta ke velocity, variable valve timing has broad-           needed, so you have to know how to perform
ened the power band, and variable lift                       the job properly. This is usually not too difficult
further fine-tunes air intake and exhaust flow               a task providing you had the correct tools, and
for even greater performance, efficiency and                 any shop specializing in Mercedes-Benz
economy. Regardless of how high-tech intake                  vehicles should have such items as a chain
and exha ust events have become, maintaining                 pin remover/installer.
basic cam/crank timing remains essential.
                                                             First Scenario
Keeping Time
                                                     _ _ _      Typically, you will need to deal with the timing
    Mercedes-Benz vehicles have always                       chain because of noise from a stretched chain
excelled in sound engineering and reliability.               or weak tensioner, or because the cylinder
From Formula 1 to Indy cars, Mercedes-Benz                   head must be removed for whatever reason.
engines have always been in the top tier. The                Either way, the timing chain has to be removed
same engineering principles that are used to                 and put back into proper synchronization upon
create a reliable ra ce engine are also used for             reassembly. In the case of noise, the job is not
production vehicles. One steadfast belief held by            as daunting as you may think. Mercedes-Benz
the company's engineers is in the reliability of             has service procedures that make this a rela-
the timing chain. The valve trains found in large            tively simple task. Many Mercedes-Benz
six cylinder, V8 and twelve cylinder engines                 engines have the timing cover cast as one unit
natural ly have more mass to move than those of              with the block, so the cover cannot be removed
little fours. This puts undue stress on the                  to access the timing chain.
camshaft drive mechanism, making a timing belt
                                                             Continued on page 20

                                                                                                          StarTuned 17
R      EP LA C E -                   We replace more parts than aftermarket brands.


E      NG I NEE RED -                            Designed to meet original OEM drawings.


M       AN U F"ACTU RED -                                   Made with same OE components as factory parts.


A ss EM B                  LED -              Completely assembled from components and not just repaired.


N       EW -            Tested to new unit standards.



QUALITY,                              RELIABILITY AND                                                  VALUE

      The quality, reliability and value of the Genuine Mercedes-Benz Remanufactured
AIC Compressor wasn't meant to be taken lightly. It is not only an exact replacement
for the original unit, it's also remanufactured and tested to meet the same strict
specifications as the original, so it performs just as well. And like all remanufactured
parts, it's covered by the Mercedes-Benz limited parts warranty.* In fact, the only detectable
difference you' ll find between a Genuine Mercedes-Benz Remanufactured AlC Compressor
and a new one is the price. Which we're sure you'll find quite refreshing.


IT'S              ALL               I N        THE               PROCESS

Remanufacturing Process (Genuine Mercedes-Benz)
 1. Dismantle core                     2. Replace key                            3. Test all                4. Replace
    and clean all ,                       components 100%                           other critical             components that
    components.                           with new OE part.                         components.                do not meet specs.



Rebuilt Process (Typical Aftermarket)
 1. Identify damaged                        2. Replace damaged                        3. Re-assemble,
    part or parts.                             part with non-OE                          test and box.
                                               part and clean.
*See your Mercedes-Benz dea ler for details and a copy of the Mercedes-Benz Spare Parts Limited Warranty.
Star tuned magazine february 2009
A QUESTION OFTIMING                                                              Continued from page 17


          lnf~bOXl    UIII'MI    ~   A8BY9T
                                                                                                                                                      Your paid subscription to
         ~~~ ~~~~~~~____~_________________
           '''==
              "hm ".=1
          ~               ,.g' ../../-                                                                                                                www.startekinfo.com will
                                                                                                          Ooc .m. ~"05~~~.!601~V'
                                                                                                                s...~mcdt
                                                                                                                                        P,g,'
                                                                                                                            SI ...... al ... dl
                                                                                                                                                  :   allow you to access WIS
          3          Remove the rags trom the    ~mln~   case recess
                                                                                                                                                      documents. Here the correct
                     rn    Otherwise. they could get pulled into the liming csse reCaSS
                     I'otlen the engine Is cranked.
                                                                                                                                                      step-by-step procedures are
          4          Tum £t1e crankshaft slOVi1y In the engine's dlraction of rOfa~on
                     (arrow) and draw In the newtlmlnr;; chain (2) unbl the ends of the
                     new timing chsln (2) canbe connected.
                     rn  flJ:, the new ~ming chain (2) is being dravm In (arrows). pull
                                                                                                                                                      laid out for you. You are also
                     out tne end oflhe old timing chain ( 1) evanly as Itbecomas tree.

          5          Cover over bming case recess WIth e clean clotl'1
                                                                                                                                                      linked to pages that let you
                     rn The dmlng case rscess must be secured against parts failing
                     down Parts that have lellen into the timing case recess must be
                     removed
                                                                                                                                                      know what special tools you
          6          ISJOetach the assembly link (01). and separate the old timing
                     chain (1) from the new timing chain (2).                                                                                         will need. The procedure for
                 m assembly link (01) must be remov.;.d The assembly link
                  The
                 Is only en aid for assembly and Is nol suitable lor engine
                 operation
          . '--~------.-'------"--.-
                                                                                                                                                      drawing in the new chain IS
                                                                                                                                                      pictured here.
: ..    _ There is a straightforward procedure, however,
         that makes replacement possible anyway. The
         first step is to remove the valve covers. Also
         remove the spark plugs to make it easier to turn
         the crankshaft by hand. You may want to start
         with the engine at TOC, it's not really necessary.
         In most Mercedes-Benz "Checking Engine
         Timing" procedures, you are asked to rotate the
         crankshaft to a specific point on the pulley. This
         is usual ly not TOC, but a specific degree mark
         past TDC . If yo u are so inclined, you can apply
         paint marks on the cam gears and adjacent
         marks on the timing case cover to check your
        work once you have changed the timing chain.
: :B! iI. _ The next step is to use the cha in separating
         tool to force out the two pins of one outer link.
         This will break the chain and leave two sid es of                                                        On this III engine, if the camshafts
         inner lin ks exposed. Install a service master link
         on the chain leading into the upper portion of the                                                       are in their home position you will be
        engine. Use one pin to attach this link to the                                                            able to install a com positioning tool
         upper side of the chain currently installed in the
         engine. Connect the other half of the service                                                            in the bocks of the com sprockets.
         master link to the new replacement chain. You                                                            The screwdriver indicates the loca-
         should now have one long continuous chain half
         installed in the engine . Grab the lower half of the
                                                                                                                  tion of one of the holes (intake
         old timing chain coming up from crankshaft                                                               com). Notice how the intake and
         toward the passenger side camshaft and pull.
         While doing this, rotate the crankshaft pulley
                                                                                                                  exhaust com lobes are facing one
         clockwise. This will draw in the chain. It is critica l                                                  another. This gives you a ballpark
         not to rotate the engine counter-clockwise at any                                                        ideo that you have the timing close.
         po int in the repair. If you do, the chain tensioner


         20 StarTuned
" ..
'      -
           ~ - ·_shouid-the;:g9mg~~tg . li~et911gh:.~·-: =_~:
                      -   - -' ,   -:,   - ', '   ~',' ..-~,:.:,-.","-~",   ' ,•. -   ".::~ ::.- .. -   - .---


                          Small scratches, stane impacts, dents and blemishes -
                          and the custa,mer's Mercedes can quickly lase the shine
                          fram its exteriar.And because that is annayance enaugh,
                          we keep th e casts far a reprir fS ,lo'y; ~:s passible - with
                          Mercedes-Benz Small Repair. Speci'~(i:~paiX rpethads mean
                          that small appearance defects vanish in nexft6 na time.
                          It gaes withaut saying that .our kits meet the high, tested
                          Mercedes-Benz quality standards that yau expect. Sa if yam
                          custamers are driving araund with a small imperfectian, it
                          may be able ta be repaired with Mercedes-Benz Small
                          Repair. Small Repair Kits are available fram yaur authorized
                          Mercedes-Benz dealer.

                          Training an the Small Repair methad s are available fram
                          Reliable Autamative Equipment. Please cantact Reliable
                          Autamative Equipment ta inquire abaut training yam
                          staff ta perfarm these repairs quickly and efficiently.




                                         RAE
                          RELIABLE AUTOMOTIVE EQ1JIPMENT, INC.     1.800.328.7855
                                                                                              StarTuned 21
A QUESTION OFTIMING




                                                                                       Look at the intake com
                                                                                       on the right and you can
                                                                                       see the camshaft timing
                                                                                       adjuster. Since the engine
                                                                                       rotates clockwise, you
                                                                                       need to turn the adjuster
                                                                                       counter-clockwise all the
                                                                                       way until it stops, then
                                                                                       engage the timing chain.



  wil l co llapse and probably all ow the cha in to                 In severe cases, this can snap off a cam
  j ump teeth on one of the sprockets, thus throw-                  sprocket! To reset the tens ioner, remove the cen-
  ing off valve tim ing. If you continu e to rotate th e            ter cap with a hex key socket, and the pre-load
  engine clockwise you will eve ntually draw in the                 spring wi ll fallout (watch out for the alum inum
  entire section of new doub le-ro ll er cha in and                 sea lin g washer). Th ese are hydraulically-assisted

Wl._
  once again see the service master link.
     At this point, you must remove the service
  master link as it is onl y intended to be used dur-
                                                                    tensioners that require engine oil pressure to add
                                                                    tension as engine rpm rises. Th e pre-load spring
                                                                    pushes on a piston that in turn pushes on the
  ing service . Install the permanent link with a                   chain tensioner guide. The piston ratchets
  chain link pin installer. The tensioner may be                    outward to apply tension. Once it ratchets out, it
  pushing on the cha in hard enough as it comes                     wi ll not return even with the spring removed. So,
  up from the crankshaft that the two ends won't                    remove the who le body of the tens ioner, pu ll the
  meet. So, you can loosen the tensioner to help                    piston out and away from the pre-load sp rin g cap .
  with the insta ll ation of the permanent link . Don't    , --   ---, Now you can mount the body of the tensioner
  take the tensioner out all the way as t hi s may                  into the tim ing case cover, making sure the
  allow enough slack for the cha in to jump time.                   alum inum sea ling washer is properly installed.
  The permanent link outer plates need to be                         Put the piston into the open ing of the tensioner
  installed and a chain ri vet insta ller must be used              body fo ll owed by the pre-load spring, then instal l
  to sta ke down the roller pins just like those of                 the cap over the spring and thread the cap into
  the other links. Rotate the engine severa l times                 the tens ioner body. Some force will be requ ired
   by hand and watch for your paint marks to be                     to compress the spring, wh ich is necessary to
   sure va lve timin g is correct.                                   keep the chain tight enough for start-up. Once
~_. At th is point it should be safe to remove the                  the engin e is running, oil pressure does the job.
   tens ioner and either insta ll a new one or reset the            That's why it's important to replace both
   old one. Resetting the tensioner is critica l. As you             alu minum seal ing washers even if you're reusing
   ran the new cha in in and the old one out, the                   the old tensioner. By the way, when ordering a
   tensioner's spring pushed outward to take up the                 new tens ioner you shou ld be aware that it does
   slack in the chain. If you were to leave it in this               not come with the threaded cap, so you will need
   position, the chain wou ld be far too tight.                     to use the cap from the old one.


       22 StarTuned
Star tuned magazine february 2009
A QU ESTION OF TI MING

                                                                     access the crankshaft sprocket and you will also
                                                                     have access to the chain gu ides . After removing
                                                                     the tensioner, va lve coverts). cha in gu ides, cam
                                                                     sprockets and oil pan, you wi ll be able to remove
                                                                     and replace the unbroke n cha in. This procedure
                                                                     also requires some special tooling since you have
                                                                     to properly align the camshafts and crankshaft.
                                                              C:::_ _ Over the years, Mercedes-Benz has used sev-
                                                                     eral different ways to assure that the camshafts
                                                                     and crankshaft are prope rly synchron ized - too
                                                                     many to be thorough ly explained in a magazin e
                                                                     article. So, we will provide a simp le overview.
                                                                     There are usually a few types of special tools to
                                                                     lock down the camshafts. Some enter t hrough
                                                                     the rear of the sprockets. An ali gnment pin pass-
                                                                     es through a hole in th e cam cap and a ho le in
                                                                     the sprocket. With variab le va lve timing comes
                                                                     the important step of setting the intake cam
                                                                     sprocket to the home position (retarded). Hold
                                                                     the camshaft itself in the locked posit ion with a
                                                                     wrench and twi st the camshaft adjuster in the
                                                                     opposite direction of t im ing chain rotation, wh ich
       Mercedes-Benz usually times its
                                                                     results in the retarded position. If there is any
       engines at a position other than                              question of a camshaft adj uster not moving
       TOC. In the case of this I I I engine,                        freely, now would be the time to change it. The
                                                                     use of non-approved oils in these engines can
       the timing pulley should be set to                            cause sludge build-up and jamming in the
       20 deg. after TOC. This puts the                              adjuster mechanism. Thi s can lead to misfires,
                                                                     poor idle and the Mll/CE l com in g on . On newer
       keyway in the crankshaft at just                              engines, special tools bolt down to the va lve
       about the I2 0 'clock position.                               cover flange on the head, and tabs lock into the
                                                                     cam sprocket, but these will be covered in future
       Now, you should be able to line                               articles . Generally, the crankshaft is located a
       up the cams.                                                  few degrees past TOC and is not locked down .

                                                                     Closing Up
       Second Scenario
                                                                        With the timing chain and camshaft adjuster in
::::JI_ _ If more extensive service work such as a cylin-
                                                                     the proper position you can start re-insta ll ing the
         der head R&R is performed, it may be easier to
                                                                     chain guides, oil pan, va lve covers and tensioner
         simply remove the timing chain as one unit. Start
                                                                     as outlined earli er. It is always a good idea to
         by removing the tens ioner. You can then remove
                                                                     rotate the engine by hand severa l ti mes to verify
         either the camshaft timing sprockets, or the
                                                                     all components are properly timed and that the
         camshafts themse lves, depending on the particu-
                                                                     chain meshes smoothly. The f inal step shou ld be
         lar engine . For instance, on the M272 motor the
                                                                     to install the spark plugs and fire up the engine,
         timing chain on ly drives the intake cam, which
                                                                     allowing time for oil press ure to reac h the
         then drives the exhaust cam by means of gears.
                                                                     tensioner before accelerating.
         In th is case, the cams will have to be removed to
         access the tim ing chain. Drop the oil pan to


        24 StarTuned
A Mercedes-Benz should be true to its origins. So turn to the Mercedes-Benz Classic
                                                                                                Center for Genuine Mercedes-Benz Classic Parts. Their experts have access to over
                                                                                                40,000 true-fitting Genuine Classic Parts of the highest quality, plus a 12-month
                                                                                                limited warranty. They sell direct, ship direct and even assist In parts specification.
               Mercedes-Benz Classic Center                                                     When you want authentic parts, only the source will do. MBUSA.com/ClasslcCenter




            To speak with our Parts Experts, call our Parts Order Desk at 1-866-MB-CLASSIC (1-866-622-5277).
            Mercedes-Benz Classic Center USA, 9 Whatney, Irvine, CA 92618

Call or vi sit for additional details and a copy of the Limited Parts Warranty.   <02008 Mercedes-Benz USA, LLC
FEATURE ARTICLE / COLLISION REPAIR




The Straight & Narrow
When evaluating chassis integrity after collision damage you need to
take the extra steps to verify straightness. The inherent value of a
Mercedes-Benz vehicle definitely makes these extra steps worthwhile.

                                                                                  the next step is to look for indirect
    Look at the collision industry         Assessment                             or secondary damage that was
statistics co mpiled in the last few
ye ars an d you will notice an                One of the first steps that is      caused by this collision. Although
increase in vehicles defined as a          often overlooked and/or taken for      we realize this is not always t he
tot al loss by insurance companies .       granted is the damage assess-          case, it is often a good idea to
The reason for this is multi-              ment. This is more than just a visu-   start pulling the frame in a linear
fa ceted . Increases in the cost of        al overview of the parts that will     direction extending the body front
pa rts, the short age of certified         need to be replaced. A deeper          to rear. Pulling fron t to rear wi ll
body techs, and collision repair           analysis should be incorporated        "stretch" the chassis into a
fac ility    tooling/environmental         into the assessment. Look at the       straighter position . Obviously,
compl iance costs have all con-            point of impact and determine its      with corners and angled frame
tri buted to the overall price of a        direction. You should think like a     panels this will not always be the
repa ir. Also, the vehicles them-          detective at this point and try to     best way to go, but it is a start.
selves often contribute to the             recreate the accident in your head .   Sometimes it is better to pull the
added cost. Exotic metals, con-            It sounds like common sense, but       framework at 90 degree angles to
struction welding technology and           this usually gives a good indication   the panel's original location . This
fastening techniques have all              of what points you should start        may take several steps as you
required retooling and training,           pulling from . Also, this may be a     change the location and / or the
wh ich adds to the overhead of any         good way to gauge from what            direction of the pull point to stay
col lision repair shop . Mercedes-         direction you should start pulling     perpendicular to the panel you are
Ben z vehicles, however, retain suf-       once the chassis has been initially    pulling. These are just some gen-
fi cient value to justify the cost of      straightened.                          eral guidelines rega rding frame
repa iring most collision damage.             Next, look for damage at the far-   alignment meant to get you think-
    Reputable shops know the               thest point from the impact. This      ing about the next step, which is
importance of returning the vehi-          gives you the total surface area of    developing a repair plan.
cl e's structu ral integrity to its pre-   all of the damaged panels . Even if
collision state. When dealing with         the damage in this area is minimal,    Measuring Up
 frame damage, it's essential to           it needs to be straightened. During
                                           the pulling process, it can be used       An old adage says, " Before you
 restore the basic framework for
                                           as a gauge of the straightness of      can go anywhere you have to
 proper chassis dynamics (such as
                                           the overall section. If the farthest   know where you are ." The same
 suspension alignment) and future
                                           point of damage after pulling has      can be said for frame straighten-
 crash-worthiness . You may ask
                                           now returned to its original shape,    ing. This next step in the repair
 yourself, "When should I check
                                           you may want to start pulling from     process involves measurin g
 chassis alignment?" and, "How
                                           another point.                         chassis alignment on a bench or
 can I do a better job of pulling that
                                              Back to assessing the damage,       "jig" against Mercedes-Benz or
 chassis into alignment?"


26 StarTuned
Vehicle Dody Informalion
                     lUrudn .£j.nz. vthld15' 9o!1)'andBodyl,lat.rlallnlollna~on
                     lor DodyslloP'. acclcl.nt UUUOI' alllllnlllram:.e camplnill

 Men;cdcs-Benz       230

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 Home

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                      Bodyfuluru

                      Mod. rn hybf1 dbO"Ystructur, Intludlng hlgh-,ltenglh sin'. alum'num and mag onium

                          • D. bCl'llbl, !font and lUI modules   ma~.      bod:)' repair easltr
                      -----~--                                   -..   ~




Before you start the pulling process you need to know what met-
als you are working with. Mercedes-Benz uses different metals
with dif ferent strength levels to achieve structural strength and
occupant safety. A visit to www.mbcollisioncenters .com and
your membership gets you this important data.




Car Bench is a Mercedes-Benz approved alignment jig for frame
straightening. There are various models available, and by visiting
www.carbenchna .com you can arrange bench rental and download
measurement specifications.
COLLISION REPAIR / SUB FRAME R&R


!iil WISI.,RA no! " .. on,                                     GJ@[gJ    the frame until you match the
                                                                         measurements. These measure-
                                                                         ments are supplied by Mercedes-
                                                                         Benz through WIS-Net, wh ich you
                                                                         can access with a paid subscrip-
                                                                        tion to www.startekinfo .com.
                                                                        Aside from having the step-by-
                                                                        step procedure to rep lace interior
                                                                         body panels, it also conta ins
                                                                         measurements for K-point frame
                                                                        diagnostic procedures. If you
                                                                         have a hard time locating the K-
                                                                        point measurement spec ifica-
                                                                        tions, try entering a chass is num-
                                                                        ber or the entire VIN and look
                                                                        under group 40.30.
                                                                           Newer vehicles util ize a different
                                                                        procedure: measuring off of an
                                                                        alignment bench. Mercedes-Benz
With a paid subscription to www.startekinfo.com. you can use            has approved two bench manufac-
WIS-Net to pull up the K-point measurement data. This infor-            turers for chass is alignment, t he
mation is only used for diagnostic purposes, particularly on            Car Bench, and the Celette chassis
older models built before the turn of the millennium. You can           alignment bench. If you have
                                                                        invested in the Celette or Car
use these measurement points to see how bad the damage is.
                                                                        Bench jig, you can access those
the bench manufacturer's specifi-                                       measurements from their web-
cations . Here is where a hard                                          sites. The Celette website is
dec ision has to be made: Is the                                        www.celette-us.com. On the home
f rame damaged beyond repair?                                           page, select the "Fixture bench
No one wants to put in all the                                          Setup Sheets" field, then select
labor to get to this point and not                                      your model chassis. There may be
repair the vehicle. Tota ls should                                      VIN number differences, so be
have been weeded out during the                                         sure to select the correct identifi-
damage estimate.                                                        cation number. The Car Bench
   On earlier Mercedes-Benz mod-                                        website is www.carbenchna.com.
els (previous to the 210 chassis),                                      From the home page, select
chassis damage was measured                                             "Support," then "Resources."
                                      Here is a Celette bench with
off of a K-point. That is, a point                                      From there, select the "+" symbol
                                      a 230 chassis set up for
within the driveshaft tunnel that                                       next to the heading "Datasheets,"
                                      measurements and pulling.
was hopefu lly the least likely to                                      followed by the type of bench you
                                      The framework setup and           are working with, the manufactur-
be hit in an accident. The K-point
                                      procedures are all available      er (Mercedes-Benz), model and
 is a diagnostic too l for body men
                                      on the website. Remember,         chassis variant if applicable.
to use to straighten frames. From
 this K-point you measure the dis-    you can use higher strength       Rental units are available from
 tance to all suspension pick-up      steels to pull lower strength     either manufacturer. These are the
 points and see if the chassis has    steel, but you cannot reverse     two chassis alignment jigs official-
 twisted. From here, you pull on      the rule.                         ly approved by Mercedes-Benz .



28 StarTu ned
They inherited our strongest genes.
Not all remanufactured parts come from such hardy stock.          re li abi lity. And they feature the same-as-new Replacement
Genu ine Mercedes-Benz Remanufactured Parts strictly adhere       Parts Limited Warranty. Access over 700 parts in 20 product
to factory specifications - fo ll owing a uniform, precis ion     lines for today's vehicles, and classics too. Offer your customers
process. In fact, all wear and tear parts are replaced with OE    affordable Genuine Mercedes-Benz Remanufactured Parts.
pa rts - tested to OE specificatio ns - for higher qua lity and   Visit mbwhelesaleparts.com or contact your dealer.
COLLISION REPAIR / SUB FRAME R&R

Bending To
Your Will
  Once the chassis is on the bench                                                                                                                                Dor; . no. tr«I~~~!'      ""'11' 1   01'
                                                                                                                                                                        s..o._~ .. ","",
and the measurements have been
taken, you can start pulling. Frame      1   Position modular members on indelC tiekl15 end 21               3      Mount    Mu~I·Z
                                                                                                                    on Side pbs (8).
                                                                                                                                      alaments M.Z 260 (arrow points towards the Iront)

                                         2   Mount side Jibs (8) on modular members.
straightening is an art developed                                                                            4      Insert   cy~ndrical   supports (10) Into Ml 260 (upper hOle)


through experience, but there are
some relatively new concerns with
Mercedes-Benz designs and metal
composition . In some cases, of
course, the damage to a panel will
be so great that straightening may
not be the best option compared              Fasten longiludln~1 portel member (9) at cylindrical supports
                                                 with bolts M12 >:35 (11 2 and 8)
                                                                         6m
                                                                                                             m
                                                                                                             ...-
                                                                                                                    lI the rear lender Is removed,
                                                                                                                    nLr~~r   'QnnQr l
                                                                                                                                                       Insert spacer (dj (Shael lniCkness


to rep lacement. In the case of
high-strength steel, this becomes
a requirement. High-boron steel is      With your paid subscription to www.startekinfo.com. you can
very difficult to reform after crash    access step-by-step instructions for alignment bench assembly
damage because it is so strong.         and measurement procedures. You also are provided with
Mercedes-Benz uses fou r grades         replacement procedures for interior structural panels as well
of steel: mild steel, high-strength     as exterior body panels.
steel , modern high-strength steel
and final ly ultra high-strength        virtually impossible to reform and                                            strength steel and weld or bond
steel. Mild stee l is much easier to    will need to be replaced. When                                                and rivet in the new sections. In
pul l. The higher strength steels can   damage is localized, it is much                                               the case of the 215 chassis, you
be pul led, but often return to the     easier to cut out the damaged sec-                                            have to be even more carefu l
pre-pulled shape . Ultra high-          tion and replace it.                                                          pulling panels since high-strength
strength steel is heat formed, so          Ultra-high strength steel is more                                          steel and mild steel is mated with
without extensive equipment it is       widely used in new Mercedes-                                                  aluminum structural panels. On a
                                        Benz chassis such as the 204, 216                                             positive note, when pulling alu-
                                        and 251 , and to a lesser degree on                                           minum Mercedes-Benz always
                                        the 164, 171, 211, 215 and 220                                                recommends replacement over
                                        chassis. The 216 chassis has                                                  repair work.
                                        incorporated even more higher-
                                        strength steels than other
                                        Mercedes-Benz models. When
                                                                                                                      In Conclusion
                                        pulling ultra high-strength steel, it                                           Your extensive experience as a
                                        will obviously react differently                                              body man will serve you well while
                                        from modern high-strength, high-                                              assessing the damage, measuring
                                        strength and mild steel. The key                                              the alignment points and during
                                        point to remember is that you can                                             the actual pulling procedure.
Here is a frame attached to             use higher-strength steels to pull                                            Simply keep in mind the
the bench. Points on the                and align lower-strength steels,                                              Mercedes-Benz recommended
chassis can be measured                 but you cannot do the opposite for                                            procedures outlined in WIS-
from here, and you can start            obvious reasons. You will simply                                              Net and the knowledge of the var-
the pulling process. On this            deform the lower-strength steels                                              ious metal compositions of the
230 chassis, you need to be             in the process. Use ultra high-                                               chassis you are working on should
aware of the different metals           strength to pull the chassis, then                                            yield a structurally-sound and trou-
and their relative strengths.           cut out the sections of ultra high-                                           ble free-repair.


30 St arTuned
Star tuned magazine february 2009
Star tuned magazine february 2009
Star tuned magazine february 2009
Star tuned magazine february 2009
Star tuned magazine february 2009
Star tuned magazine february 2009

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Star tuned magazine february 2009

  • 2. TO OUR READERS IN THIS ISSUE We lcome to StarTuned, th e magazine for independent service 4 ANOTHER CHANCETO BURN tech nicians working on Mercedes- Just like a blacksmith's bellows, the Mercedes-Benz AIS Be nz veh icles. You r Me rcedes- Benz "fans the flames," promoting rapid oxidat io n of pollutants dea ler sponsors StarTuned and in the exhaust stream. provides the information coming your way in each issue . Mercedes-Benz wants to prese nt the inform ation you need to know to 10 SAFE & SECURE - diagnose and repa ir Mercedes-Benz MERCEDES-BENZ PNEUMATIC cars accurate ly, qu ickly and the f irst CENTRAL LOCKING t ime ; text, graph ics, on-l ine and other One of the convenience features used most by your techn ica l sources comb ine to make customers is the central locking system. Years ago, this possib le. M-B took a completely different approac h to t his by Feature articles, derive d from making it pneumatic instead of electrical. approve d company sources , focus on bein g useful and interesti ng. Our digest of technica l information can help you so lve unant icipated 16 A QUESTION OF TIMING prob lems qu ickly and expertly. Mercedes- Benz timing chains and tensioners last Our list of Me rce des-Benz dealers and last. But, given the tremendous numbe r of can help you f ind Genuine miles people put on these vehicles, they will need Merced es-Benz Parts. attention sooner or later. We wa nt StarTuned to be both he lpfu l and informative, so please let us know just what kinds of features and other diagnostic services you'd 26 THE STRAIGHT & NARROW like to see in it. We'l l continue to When evaluating chassis integrity after collis ion damage bring you selected service bu ll etins you need to take the extra steps to verify st raightness. from Me rcedes-Benz and artic les The inherent value of a Mercedes-Benz veh icle definitely covering the different systems on makes these extra steps worthwhile. these vehicles. Send your suggestions, questions or comments to us at: StarTuned 31 GENUINE MERCEDES-BENZ One Mercedes Drive PARTS ... NEARBY Mo ntvale, New Jersey 07645 Wherever you are in the United States, there's a nearby Phone: 1 8002256 262 , ext. 7112 source of genuine factory parts for your customers' e-ma il : StarTuned@mbusa.com Mercedes-Benz veh icles. StarTuned is a quarterly publication of Mercedes-Benz USA, LLC (" MBU SA"). N o pa r t o f this news lette r may be rep rodu ced without the express written permission of MBUSA. Ed i to r ia I and Circulation Offices: 598 Pine Po int Dri ve . Ak ron. Ohio 44333. Caution: Vehicle servicing performed by untrained persons could re sui tin se ri ous injur y to t h ose pe r so ns or others. Informatio n contained in this news letter is intended fo r use by tra ined, pro fess iona l auto repa i r technic i ans ONLY. Th is informat ion is prov i ded to i n form these tec hnic i ans o f co ndi t i ons wh i ch m ay occur in some ve hi c le s or to prov ide inform a t io n wh i ch cou ld assist th em in prope r servic ing of th ese veh i c l es. Proper ly train ed tech nician s have til e equ i pm en t , t oo ls, safe t y ins truc tio ns, and k now-how to perfo r m repairs correct ly and safely . If a cond iti on is desc ri be d, DO NOT ass um e tha t a topi c covered in these pages automa t ic all y ap pli es to yo ur ve hi c le or that you r veh icle has th at condition. StarTuned is a registered trademark of MBUSA.
  • 3. STARTUNED Information for the Independent Mercedes- Benz Service Professional February 2009 U.s. $6.00 € 1 2.50 Volume 9 Number I Group Publisher Contributing Editor MBUSA Technica l Production Manager Christoph er M. Ayers, Jr. Chip Keen Content Advisor Devon Ayers cayers@cmacomm.com ckeen@cmacomm .com Donald Rotolo dayers@cmacomm.com Donald.Rotolo@mbusa.com Senior Project Director Contributing Editor Circulation Manager Tamra Ayers Ke rry Jonsson MBUSA Project Manager Joann Turner tayers@c macomm.com kjonnson@cmacomm.com Stephen Langelotti j turner@cmacomm .com Stephen .Langelotti@mbusa .com Editorial Director Contributing Editor List Consultant Bob Freudenberger T Nash om Art Director NFocus bfreud@cmacomm .com tnash@cmacomm.com Jef Sturm jsturm@cmacomm.com
  • 5. Just like a blacksmith's bellows, the Mercedes-Benz AIS "fans the flames," promoting rapid oxidation of pollutants in the exhaust stream Whether you believe technological the fire in the old two-way catalytic developments are motivated by tightening converter. In th e early '80s when the government regulations, or by the desire to three-way cat became popular, the air add va lue for new-car buyers, there's no was piped into the cat downstream of the doubt that they are coming along at an redu ction section after the engine warmed ever-increasing rate. Secondary air injection up so that it wouldn't interfere with the systems, however, have a long history - reaction that broke down NOx, yet was they've been fighting air pollution since the available for the oxidation section. 1970s. Of course, they're way different today from what they were then . Seltless Originally, a belt-drive n pump forced air in to the exhaust manifold to help oxidize A modern Mercedes-Ben z secondary AIS escaping HC and CO. This was taken one (Air Injection System) does away with that step further when that air was used to fee d energy-wasting and space-hogging belt in On VB engines, the secondary air system is easy to test. Everything is right in front of you. Here we have the air pump, shut-off valves and switch-over solenoid, all nicely accessible. StarTuned 05
  • 6. SECONDARY AIR INJECTION SYSTEMS favor of an electrically-driven pump . Th is also allows much more precise control of airfl ow, which is necessary as emissions regulations continue to become stricter on both federal and state levels, and as the quest fo r improved fuel efficiency continues. The secondary air pump motor is only activat- ed when the engine is relatively co ld - below 60 deg. F. It is only commanded on fo r up to two and a half minutes. This is sufficient to warm up the catalytic converters. The pump receives its power supply from the secondary air pump relay, which is operated by the ME contro l unit. The system is also activated during closed-loop operation, but on ly to test the system's abilit y to pump air into the exhaust - the ME contro l unit looks at the reaction of the 02 sensors. There is one exception to th is rule. Early 111 Eva engines (four-cylinder supercharged) do not use an electric pump. The ME control unit uses On supercharged models, the the supercharger to genera te t he necessary pres- sure/flow of fresh air to the exhaust. On models compressor generates the air that is with an electronically-controlled "compresso r" supplied to the exhaust ports through clutch, the clutch is activated at engine tempera- tures below 60 deg. F., and can be kept engaged this shut-off valve. Notice the solenoid for about two and one half mi nutes . On later 111 mounted nearby that supplies vacuum engines, there is no supercharger clutch, so the to open the shut-off valve. compressor is always spinning. The recirculation flap is held closed to allow the compressor to make the relatively sma ll amount of air pres- sure/flow that the exhaust air inject ion requi res. When the secondary air pump motor is activated cold, or you cause it to activate, you can measure the amp draw of the pump. As you can see here, around 26 amps should be your reading with a normal motor. If it is lower; the pump por- tion is probably worn. If the amp reading is too high (fused 40 amps) the motor may be seizing up. 06 StarTuned
  • 7. Your paid subscription to www.startekinfo.com allows you to pull up the wiring diagram for the engine management system. Look at components K17 (relay) and MJJ (air pump motor), and you should be able to come up with a diagnostic plan to activate the relay and test the air pump. Shut-off valve stream, the 02 sensors register the high oxygen content in the fresh air and this signal causes the From the pump, the air is directed to a shut-off ME control unit to assume that the engine is run- valve. This valve is vacuum-controlled, and is nor- ning lean . The ME's adaptation programming mally cl osed to block exhaust gases from reach- tries to compensate for the lean condition by ing the pump when the system is not energized. adding fuel. The ME looks for a lambda value On four- and six-cylinder engines, there is only change of 25%. If the change is less than 25%, one shut-off valve, but there are two on eight- the control unit determines that there is low flow and twelve-cylinder models. When the system is of the secondary air injection system and flags a active, a switch-over solenoid supplies vacuum to code of P041O, or one of its variants. This could the shut-off valve(s) . This solenoid is ground-con- be caused by no voltage to the secondary air trolled by the ME. Remember, with engine tem- pump, or a weak pump. An inoperable switch- perature below 60 deg. F. the switch-over sole- over solenoid or a stuck shut-off valve can also noid is grounded, which supplies vacuum to the cause codes. If all these components are func- shut-off valves, opening them. Air is then sup- tioning properly, you may still have the problem plied to the secondary air passages cast into the of blocked passages in the cylinder heads. How cylinder head and exits into the exhaust ports. are you going to determine what's at fault? This oxygen rich air mixes at the earliest point with the hottest exhaust gases and promotes Codes and testing continued combustion. The heat generated from this process in the exhaust manifold heats up the Since problems in the secondary air system catalytic converter fast and therefore reduces usually do not cause drivability symptoms, you overall emissions quickly. will probably be diagnosing a code in the P0410 :JIII._ Being an emissions control system, AIS must range. The customer will more than likely bring in have self-diagnostic capabilities. So, has its own the vehicle with a CEl (Check Engine light) or monitor. Both the secondary air pump and the Mil (Malfunction Indicator lamp) on. You are switch-over solenoid are activated during a nor- going to have to test components, and you are mal drive cycle. Once the pump supplies fresh air going to have to start somewhere. Having a through t he shut-off valve into the exhaust Compact III or Basic is a tremendous help when StarTuned 07
  • 8. SECONDARY AIR INJECTION it comes to diagnosing any prob lem with a Mercedes- Benz system, but we believe you need to back up any scan tool diagnostics with direct component testing for verifica t ion. --..,.,,-- Testing the pump is fa irly simple. Remove the engine covers and provide power to the motor connecto r. You shou ld hear a loud whirring noise. Whenever you compress air, even though fi ltered, you are going to condense water, espe- cia lly in high-humidity climate s. Thi s moisture can get into the electrica l portion of the motor and ca use failures . Th is is why the motor is usually mounted on the engin e. The heat shou ld cause any bu ilt-up moisture to evapo- rate. The current draw of a good pump w ill be 25 to 26 amps. Any lower and you're probably not pumping much air, and anything higher and The switch-over solenoid receives the motor is sta rting to se ize . manifold vacuum, and, when :::!I._ If you are lu cky enough to have the vehic le energized, directs this vacuum to the overn ight, you can ve rify the air pump relay operation. The pump power supp ly wire should shut-off valve. You can energize this see battery vo ltage within a few seconds of a solenoid through the SDS software in co ld start. This vo ltage can remain on for up to 150 seconds. If vo ltage is low or not there at your Compact III, or simply ground it al l, yo u will need to locate the secondary air with a test light and check for vacuum pump relay. You can manua lly ground the relay and see that volt age is supp li ed to the pump. at the shut-off valve. With a pa id subscription to www.starteki nfo.com. you can retrieve a wirin g diagra m for the veh icle and component loca- What does the 02 sensor say? t ion usi ng Star Finder. As mentioned earli er, the relay is contro ll ed by th e ME. With your To test the shut-off va lve, you can app ly Compact III or Basic, you can command the vacuum to it with a hand-he ld vac uum pump - it re lay on even if the engine is already warmed shou ld hold. How wi ll you verify that it is actually up. Or, you can apply a test li ght to the ground open? You cou ld remove and phys ica ll y watch fo r contro l of the relay. You shou ld hear the relay movement, but there are better methods. You click and the pump run . Th e current draw of can app ly vacuum to the va lve and watch the the relay is around 100mA. If th is is not the front (upstream) 02 senso r signa l. It shou ld drop case, ve rify that you have vo ltage to both the to 0 mV with the secondary air pump command- control coil and switched circuit of the relay. ed on and vacuum appl ied to the shut-off va lve. - - -- If everything so far is in work in g order, you If the 02 sensor reads a lean condition, but does will want to test the switc h-over so lenoid and not drop to zero, you can assume that the shut-off va lves. The soleno id va lve is contro ll ed shut-off va lve is work ing, but there may be an by t he ME, so the Compact III or Basic scan additiona l prob lem. Th e ME contro l unit looks for too l will be ab le to activate the so lenoid, or you the Lambda (fuel trim) reading to compe nsate for can once again manually ground the so lenoid the fa lse lean cond ition by add ing 25% more f uel. with a grounded test light whi le the engine is If the secondary air passages are clogged or runn ing. Yo u should measure manifold vacuum restricted in the cylind er head, the 02 sensor wi ll at the shut-off va lves. not see the false lea n cond it ion and as a result 08 StarTuned
  • 9. You can apply vacuum to the shut-off valve and see if it holds. This should also open the valve. If you remove the hose from the air pump motor you should fee l exhaust coming out of the valve while the engine is running. ' - -1111111 -lolxI II6lilil the ME wi ll set a code for low secondary air flow. Vehicle ~- ... ontrol unit I This is one of the more difficult problems to IModel ! MEl IA c t iva t ions ~' R AIR pump repair. Short of removing the cylinder head for a m- AIR pump ~ ~ ~ t99 025 voltage r ig h t Ie f t .mv S tOFF mV I thorough cleaning, you wi ll have to find a way to clear the carbon bu ilt-up in the intake passages. C:: =. _ With a little luck and some good chemicals you ~ - 7t- 1 025 vol tage drops below 40 mV wi t hi n r---- may be able to clear the passages in the cylinder ~ 170 ( 38-p ~~ynds?Fl N <ltI FF I-- - - - - head without removal. Remove the shut-off ? va lves and pour a reasonab le amount of cleaning solution down the ports . You can remove the exhau st manifolds and plug off the secondary air ports, but this is not necessary. You will have to !J ~ ~ fWiiil ~ 1J !J . let the cleaning solution sit over night. It also make take a few appl ications before the passages are clear, but after softening up the Using your Compact III or Basic carbo n in the ports, apply shop air pressure to the shut-off va lve exhaust ports and you shou ld scan tool, you can perform a be able to open up the passages. If not, the secondary air ~ow test while cylinder head wi ll need to be removed for better access to the ports. the engine is running. Even on older vehicles such as this I 29 You can do it chassis, you can use the HHT Although pol lution contro l devices add com- software to command the plexity to an engine's air/fuel/ignition manage- secondary air system on and ment system, the above shou ld serve to illustrate that as long as you understand how any part of see the reaction of the 0 2 that system works, you can follow a logica l sensors. process to come up with an accurate diagnosis . That capabi lity wil l make yo u popular among you r custo mers. One more thing: Think about adding the pa ssages of the AIS to any ca rbon-cleaning service you offer. StarTuned 09
  • 10. FEATURE ARTICLE Mercedes- Benz vehic les have always had some uni que features . Along with reliability, longevity, safety and performance, they've hel ped make these engin eerin g masterpieces some of the most sought-after ve hicl es in th e world. One unique feature introd uced in the 1960s is the pneumatic centra l lock- ing system, wh ich, as the name imp lies, does not use the electro-mechanical actuators othe r manufacturers emp loy. In stead, it uses a co mbination of vac- uum and pressure to move the door lock actuators quietly and dependably. It has with stood the test of t im e and co nt inu es to this very day. As with any unique system, however, there is a certa in leve l of fa milia rity that is neces- sary in order to diagnose and repair the system. 10 StarTuned
  • 11. Histo rical Perspective Th e ea rliest reference we can find to pneumatic centra l locking in Mercedes-Benz arc hives is from over 40 years ago. Back then, engin e intake manifold vacuum stored in tanks did the lock in g, but the system soon evo lved to use comb ination vac uum /press ure pumps to supp ly the force needed. From 1983 onward, the change from vacuum to pressure is accomplished by electrically reversing the rotation of the motor - negative contro l vo ltage for vacuum, pos itive for pressure. Previously, this had been done by means of a switching va lve . A typ ica l pump, by the way, shou ld produce .5 Bar (7 psi) with in two or three seco nd s. StarTuned I I
  • 12. PNEUMATIC DOOR LOCl( S With a paid subscription to www.startekinfo.com. you have access to W/S ~1IlJa.otP"''''. Doe ,no QTIIO.2O+OQOS.01. PtIgI t ot ' (Workshop Information I o".m'"' L_ _ System), which will allow you to pull up on operational schematic of the central locking system. This shows all the PBO,1(J.204 1·09 components involved in AV 1 As/1 A2dl1 2 Top 199( wmdON antenna ampliflof Remote control key Lell fronl door fR receiver N 1043 N6911 N6912 Reaf SAM control module Loti front door con/rol module Right lront door control module fV13 SOOIf Electronic ignition switch con /rol module Left fron l door lock SWitch (CA 8 <D (valid for Jeft-hand steer/no) commanding the PSE mod- I A26f2 Right front door fR receiver N10 Overfle8d con/rol panel control CD A37 PSE control module (combined) module . 581/1 Rk,Jht front door lock SWitch (CA /._ /"" ... . . _ ..... ,.. .......>-...1_ • ule to lock/unlock the doors. SIIHcIH ~OO SE CI65OO1C L 600 '.m 211),175 EnoineM "ueo Press ure in the system is relieved in 15 to 20 seconds one quick tip, however: If th e veh icle has an EDW after the pump stops . If there's a heavy leak, the alarm system, you can disconnect the intermediate electronics that contro l it switch it off in 2 5 to 60 plug of the EDW cab le harness from the connector seconds. (M14/1x2, or M14/2x2) and connect the central Since about 1986, most M-B cars have had what's locking cab le harness directly to the supp ly pump. If called the "multi-point" (also called "3- Point") system. ce ntral locking works okay now, it's time to delve If you 're not sure what you're dealing with, go to the into the EDW. passenger's door and unlock. If all the other doors do the same, yo u' ve got multi-point. If not, eith er you're PSE Modern System Operation working on a car with the old er single-point syste m (which unlocks on ly from the driver's door), or there's At the heart of the centra l locking system is the a problem. But since yo u' ve been presented with a pneumatic control unit, which is in total control of compla int about this feature, you may be unable to the pneumatic portion of the system, and the vac u- get any action out of it whatsoever. That means um/pressure pump is mounted in side it. It also you've got to dig deeper. plays a role in operating the Clos ing Ass ist (CA). Around 1990, IRCL appeared, which meant the The PSE module is usually mounted under the rear locking function cou ld be operated by either the door seat on sedans and in the trunk on smaller coupes. lock switches, or an infra-red remote. The PSE As the PSE module evolved, so have its inputs - (Pneumatic System Equipment) modu le received all of the in puts and outputs to command the door locks. By '96, tne door switcn contacts were elimin ated, and C::_. more than just direct switch inputs command it. Nylon hose is used to connect all of these com- ponents and route vac uum and pressure through- the RCL (Radio Central Locking) module took control. out the centra l locking and clos i ng assist systems. l:1li._ The integration of centra l locking with anti-theft and These hoses direct vacuum/pressure from the PSE modu le to the individual door lock actuators. They remote contro l systems evolved as the years went by, and is quite complex with dozens of variations. Since have a single port on one side of a diaphragm. a magazine article cannot possibly provide all the Supplying vacuum to it moves the actuator to details, you will definitely need www.startekinfo.com. either the lock or unlock position . Supplying pres- and WIS for specific information on the model at sure to the same port does the opposite. As you hand. Here, we will cover the basic principles and sig- can imagine, this needs to be a "closed" system . nificant addit ion s to give you a roadmap . We 'll offer Any leaks can cause malfun ction. 12 StarTuned
  • 13. I~ hF8np" ii HHlWIN I!II:lEl ... C:'I" ~ Your Compact III or basic Vehicle ontrol unit I scan tool can access rcurrent PSE Functions data that includes version IFilter stal I---::---:!C:-o-n~t-r-o-:-l-m-o-:-d-u':"'"1e-v-e-r-s""'i'-o-n--l DTC memory Actual Values 0245458532 - ./- identification, diagnostic Version coding trouble codes, actual values, actuations and coding. This is an excellent way diagnosis <lIt~ to check multiple switch inputs, even those from other control units, without having to test each individual circuit. ---"_ _ As mentioned, from the early '90s the PSE module received all of the inputs and outputs to command the door locks . Starting with the early versions, one of the basic commands to be seen by the PSE mod- ule are those from the left and right door switches, which are within the pneumatic actuators. Rotating the key in the door lock or actuating the lock button atop the door signa ls the PSE. There is one switch conta ct for the lock command and another for unlock, and they are wired together with the trunk lock switch. Any of these inputs can switch the signal voltage of the PSE module to ground. When the mod- ule se es t his, it wi ll eith er lock or unlock the doors . There are other switched inputs, but most of them are for determining door and trunk latch positions . ...-- - - Later PSE modules have self-diagnostic capabi lit ies . It can store codes and data even with systems as far back as HHT, which is incorporated into the Compact III SDS system. You can see multiple switched inputs at a glance. You can monitor the lock and un lock command switches in each individual latch, trunk By monitoring the SN I and SN2 signals, tumbler, trunk lid position, individual door position and inte rior CL switches. Since there can be varia- you can evaluate the command to the t ions dep ending on veh icle options, the PSE module PSE module to both lock and unlock the needs to be version coded if replaced. Some vehicles have CA (Closing Assist), others have RCL (Remote doors. You do not need to use an oscillo- Central Locking) or CF (Comfort Lock system) scope to monitor these signals. A DMM options. C _ _ If the vehicle is equipped with Infra-Red (IR) remote will work fine. You are looking for a I 2V controls, there are some differences in the way the signal on each of these wires. StarTuned 13
  • 14. PNEUMATIC DOOR LOCKS system works. The basic door lock/ unl ock switch Testing the System signa ls are supplemented with door switch com- mands referred to as SN1 and SN2 signa ls, wh ich C=-_ If the pneumatic central lock ing system is not function in g properly, one of the first steps is to find originate in the Remote Centra l Lock ing (RCL) mod- out if there is a problem with the pneumatic system - ule. Either can co mmand the doors to lock/ unlo ck. the vacuum/pressure pump, nylon lines, or any of the By '96, the door switch contacts were elimin ated. three to five actuators - such as a leak, bind ing, or The RCL has taken ove r for these manual contro ls. seizing. This can be done fairl y easily at the PSE This means the RCL is in control of the door locks con trol module . You will notice a single large line and the signa Is to the PSE module have to be tested in order to determine if the PS E is work in g. These com ing out of the module and feeding one of two SN 1 and SN2 signa ls are also passed on to the ATA (Anti-Theft Alarm) system to confirm that an accept- able remote opened the doors before the engin e is all owed to sta rt (as of '98 w ith SmarKey, engi ne start ing is a sepe rate function fro m CL and ATA). Knowing th is can be helpful in diagnosing the PSE function if it is not work ing. Open the driver's side window, close the hood, trunk and all the doors. All ow the vehicle 's alarm to arm itself. Then, use the remote to open the doors. If the doors do not unlock, reach in thro ugh the win dow and try to start the engine. If it starts, you know the RCL signal made it to the ATA mod ule and therefore must have made it to the PSE mod ule. Th e module sho uld have unl ocked t he doors. If the engin e does not start, you may have a prob lem with the RCL system. Monitor the vo ltages on SN 1 and SN2 and see if th e 12V sig- nals get pulled to ground for eith er t he lock or unlock command. c:z_ _ A later evolution of the system is the Conven ience Feature (C F). This integrated the operation of many body contro ls into one contro l unit, in cluding power Looking at these signals on a dual windows, power door locks and power slidin g pop-up roof. The CF contro l unit directly contro ls the win- trace scope allows you to see the lock dows. Door locks are sti ll controll ed by t he PSE unit, command (upper trace) and unlock but it receives commands from either the door switches or t he CF contro l unit. After '96 when the command (lower trace). As you can see, door switches were eliminated, the Drive the I 2 V signal gets pulled to ground Authorization System (DAS) radio frequency/Infrared (IR) contro l module took over command ing the PSE when the door locks are actuated, in unit to operate the power door locks. this case by the RCL unit as the remote CII_ _ Another feature close ly related to the PSE system is Closing Assist (CA), wh ich uses its own separate button is pushed to open and close the co ntrol unit that is referred to as the CA supp ly doors. The signals are there, but the pump. It is only used for lock in g, not for unlocking. The goal is to continue to close the door all the way pneumatic pump did not turn on. after latc h con tacts the door j amb. A door micro- At this point check for powers and switch ind icates whe n the door is alm ost closed and th is signals the CA system to supp ly vac u- grounds to the PSE unit. If they are um/pressure to the CA actuators in the door latch good, replace the PSE module. assemb lies . 14 StarTuned
  • 16. FEATURE ARTICLE Mercedes-Benz timing chains and tensioners lost and lost. But, given the tremendous number of miles people put on these vehicles, they will need attention sooner or later 1 Stal-Tuned 6
  • 17. tion of Timing In order for a four-cycle engine to work, marginal, and making replacement at regular there must be precise coordination among the intervals necessary. On the other hand, in a intake, compression, power and exhaust strokes . properly-maintained vehicle timing chains and Advances in engine technology have helped related hardware can last well over 200,000 increase performance throughout the rpm range. miles. Eventually, however, wear will reach the Variab le intake manifold runners optimize air point where diagnosis and replacement wi ll be inta ke velocity, variable valve timing has broad- needed, so you have to know how to perform ened the power band, and variable lift the job properly. This is usually not too difficult further fine-tunes air intake and exhaust flow a task providing you had the correct tools, and for even greater performance, efficiency and any shop specializing in Mercedes-Benz economy. Regardless of how high-tech intake vehicles should have such items as a chain and exha ust events have become, maintaining pin remover/installer. basic cam/crank timing remains essential. First Scenario Keeping Time _ _ _ Typically, you will need to deal with the timing Mercedes-Benz vehicles have always chain because of noise from a stretched chain excelled in sound engineering and reliability. or weak tensioner, or because the cylinder From Formula 1 to Indy cars, Mercedes-Benz head must be removed for whatever reason. engines have always been in the top tier. The Either way, the timing chain has to be removed same engineering principles that are used to and put back into proper synchronization upon create a reliable ra ce engine are also used for reassembly. In the case of noise, the job is not production vehicles. One steadfast belief held by as daunting as you may think. Mercedes-Benz the company's engineers is in the reliability of has service procedures that make this a rela- the timing chain. The valve trains found in large tively simple task. Many Mercedes-Benz six cylinder, V8 and twelve cylinder engines engines have the timing cover cast as one unit natural ly have more mass to move than those of with the block, so the cover cannot be removed little fours. This puts undue stress on the to access the timing chain. camshaft drive mechanism, making a timing belt Continued on page 20 StarTuned 17
  • 18. R EP LA C E - We replace more parts than aftermarket brands. E NG I NEE RED - Designed to meet original OEM drawings. M AN U F"ACTU RED - Made with same OE components as factory parts. A ss EM B LED - Completely assembled from components and not just repaired. N EW - Tested to new unit standards. QUALITY, RELIABILITY AND VALUE The quality, reliability and value of the Genuine Mercedes-Benz Remanufactured AIC Compressor wasn't meant to be taken lightly. It is not only an exact replacement for the original unit, it's also remanufactured and tested to meet the same strict specifications as the original, so it performs just as well. And like all remanufactured parts, it's covered by the Mercedes-Benz limited parts warranty.* In fact, the only detectable difference you' ll find between a Genuine Mercedes-Benz Remanufactured AlC Compressor and a new one is the price. Which we're sure you'll find quite refreshing. IT'S ALL I N THE PROCESS Remanufacturing Process (Genuine Mercedes-Benz) 1. Dismantle core 2. Replace key 3. Test all 4. Replace and clean all , components 100% other critical components that components. with new OE part. components. do not meet specs. Rebuilt Process (Typical Aftermarket) 1. Identify damaged 2. Replace damaged 3. Re-assemble, part or parts. part with non-OE test and box. part and clean. *See your Mercedes-Benz dea ler for details and a copy of the Mercedes-Benz Spare Parts Limited Warranty.
  • 20. A QUESTION OFTIMING Continued from page 17 lnf~bOXl UIII'MI ~ A8BY9T Your paid subscription to ~~~ ~~~~~~~____~_________________ '''== "hm ".=1 ~ ,.g' ../../- www.startekinfo.com will Ooc .m. ~"05~~~.!601~V' s...~mcdt P,g,' SI ...... al ... dl : allow you to access WIS 3 Remove the rags trom the ~mln~ case recess documents. Here the correct rn Otherwise. they could get pulled into the liming csse reCaSS I'otlen the engine Is cranked. step-by-step procedures are 4 Tum £t1e crankshaft slOVi1y In the engine's dlraction of rOfa~on (arrow) and draw In the newtlmlnr;; chain (2) unbl the ends of the new timing chsln (2) canbe connected. rn flJ:, the new ~ming chain (2) is being dravm In (arrows). pull laid out for you. You are also out tne end oflhe old timing chain ( 1) evanly as Itbecomas tree. 5 Cover over bming case recess WIth e clean clotl'1 linked to pages that let you rn The dmlng case rscess must be secured against parts failing down Parts that have lellen into the timing case recess must be removed know what special tools you 6 ISJOetach the assembly link (01). and separate the old timing chain (1) from the new timing chain (2). will need. The procedure for m assembly link (01) must be remov.;.d The assembly link The Is only en aid for assembly and Is nol suitable lor engine operation . '--~------.-'------"--.- drawing in the new chain IS pictured here. : .. _ There is a straightforward procedure, however, that makes replacement possible anyway. The first step is to remove the valve covers. Also remove the spark plugs to make it easier to turn the crankshaft by hand. You may want to start with the engine at TOC, it's not really necessary. In most Mercedes-Benz "Checking Engine Timing" procedures, you are asked to rotate the crankshaft to a specific point on the pulley. This is usual ly not TOC, but a specific degree mark past TDC . If yo u are so inclined, you can apply paint marks on the cam gears and adjacent marks on the timing case cover to check your work once you have changed the timing chain. : :B! iI. _ The next step is to use the cha in separating tool to force out the two pins of one outer link. This will break the chain and leave two sid es of On this III engine, if the camshafts inner lin ks exposed. Install a service master link on the chain leading into the upper portion of the are in their home position you will be engine. Use one pin to attach this link to the able to install a com positioning tool upper side of the chain currently installed in the engine. Connect the other half of the service in the bocks of the com sprockets. master link to the new replacement chain. You The screwdriver indicates the loca- should now have one long continuous chain half installed in the engine . Grab the lower half of the tion of one of the holes (intake old timing chain coming up from crankshaft com). Notice how the intake and toward the passenger side camshaft and pull. While doing this, rotate the crankshaft pulley exhaust com lobes are facing one clockwise. This will draw in the chain. It is critica l another. This gives you a ballpark not to rotate the engine counter-clockwise at any ideo that you have the timing close. po int in the repair. If you do, the chain tensioner 20 StarTuned
  • 21. " .. ' - ~ - ·_shouid-the;:g9mg~~tg . li~et911gh:.~·-: =_~: - - -' , -:, - ', ' ~',' ..-~,:.:,-.","-~", ' ,•. - ".::~ ::.- .. - - .--- Small scratches, stane impacts, dents and blemishes - and the custa,mer's Mercedes can quickly lase the shine fram its exteriar.And because that is annayance enaugh, we keep th e casts far a reprir fS ,lo'y; ~:s passible - with Mercedes-Benz Small Repair. Speci'~(i:~paiX rpethads mean that small appearance defects vanish in nexft6 na time. It gaes withaut saying that .our kits meet the high, tested Mercedes-Benz quality standards that yau expect. Sa if yam custamers are driving araund with a small imperfectian, it may be able ta be repaired with Mercedes-Benz Small Repair. Small Repair Kits are available fram yaur authorized Mercedes-Benz dealer. Training an the Small Repair methad s are available fram Reliable Autamative Equipment. Please cantact Reliable Autamative Equipment ta inquire abaut training yam staff ta perfarm these repairs quickly and efficiently. RAE RELIABLE AUTOMOTIVE EQ1JIPMENT, INC. 1.800.328.7855 StarTuned 21
  • 22. A QUESTION OFTIMING Look at the intake com on the right and you can see the camshaft timing adjuster. Since the engine rotates clockwise, you need to turn the adjuster counter-clockwise all the way until it stops, then engage the timing chain. wil l co llapse and probably all ow the cha in to In severe cases, this can snap off a cam j ump teeth on one of the sprockets, thus throw- sprocket! To reset the tens ioner, remove the cen- ing off valve tim ing. If you continu e to rotate th e ter cap with a hex key socket, and the pre-load engine clockwise you will eve ntually draw in the spring wi ll fallout (watch out for the alum inum entire section of new doub le-ro ll er cha in and sea lin g washer). Th ese are hydraulically-assisted Wl._ once again see the service master link. At this point, you must remove the service master link as it is onl y intended to be used dur- tensioners that require engine oil pressure to add tension as engine rpm rises. Th e pre-load spring pushes on a piston that in turn pushes on the ing service . Install the permanent link with a chain tensioner guide. The piston ratchets chain link pin installer. The tensioner may be outward to apply tension. Once it ratchets out, it pushing on the cha in hard enough as it comes wi ll not return even with the spring removed. So, up from the crankshaft that the two ends won't remove the who le body of the tens ioner, pu ll the meet. So, you can loosen the tensioner to help piston out and away from the pre-load sp rin g cap . with the insta ll ation of the permanent link . Don't , -- ---, Now you can mount the body of the tensioner take the tensioner out all the way as t hi s may into the tim ing case cover, making sure the allow enough slack for the cha in to jump time. alum inum sea ling washer is properly installed. The permanent link outer plates need to be Put the piston into the open ing of the tensioner installed and a chain ri vet insta ller must be used body fo ll owed by the pre-load spring, then instal l to sta ke down the roller pins just like those of the cap over the spring and thread the cap into the other links. Rotate the engine severa l times the tens ioner body. Some force will be requ ired by hand and watch for your paint marks to be to compress the spring, wh ich is necessary to sure va lve timin g is correct. keep the chain tight enough for start-up. Once ~_. At th is point it should be safe to remove the the engin e is running, oil pressure does the job. tens ioner and either insta ll a new one or reset the That's why it's important to replace both old one. Resetting the tensioner is critica l. As you alu minum seal ing washers even if you're reusing ran the new cha in in and the old one out, the the old tensioner. By the way, when ordering a tensioner's spring pushed outward to take up the new tens ioner you shou ld be aware that it does slack in the chain. If you were to leave it in this not come with the threaded cap, so you will need position, the chain wou ld be far too tight. to use the cap from the old one. 22 StarTuned
  • 24. A QU ESTION OF TI MING access the crankshaft sprocket and you will also have access to the chain gu ides . After removing the tensioner, va lve coverts). cha in gu ides, cam sprockets and oil pan, you wi ll be able to remove and replace the unbroke n cha in. This procedure also requires some special tooling since you have to properly align the camshafts and crankshaft. C:::_ _ Over the years, Mercedes-Benz has used sev- eral different ways to assure that the camshafts and crankshaft are prope rly synchron ized - too many to be thorough ly explained in a magazin e article. So, we will provide a simp le overview. There are usually a few types of special tools to lock down the camshafts. Some enter t hrough the rear of the sprockets. An ali gnment pin pass- es through a hole in th e cam cap and a ho le in the sprocket. With variab le va lve timing comes the important step of setting the intake cam sprocket to the home position (retarded). Hold the camshaft itself in the locked posit ion with a wrench and twi st the camshaft adjuster in the opposite direction of t im ing chain rotation, wh ich Mercedes-Benz usually times its results in the retarded position. If there is any engines at a position other than question of a camshaft adj uster not moving TOC. In the case of this I I I engine, freely, now would be the time to change it. The use of non-approved oils in these engines can the timing pulley should be set to cause sludge build-up and jamming in the 20 deg. after TOC. This puts the adjuster mechanism. Thi s can lead to misfires, poor idle and the Mll/CE l com in g on . On newer keyway in the crankshaft at just engines, special tools bolt down to the va lve about the I2 0 'clock position. cover flange on the head, and tabs lock into the cam sprocket, but these will be covered in future Now, you should be able to line articles . Generally, the crankshaft is located a up the cams. few degrees past TOC and is not locked down . Closing Up Second Scenario With the timing chain and camshaft adjuster in ::::JI_ _ If more extensive service work such as a cylin- the proper position you can start re-insta ll ing the der head R&R is performed, it may be easier to chain guides, oil pan, va lve covers and tensioner simply remove the timing chain as one unit. Start as outlined earli er. It is always a good idea to by removing the tens ioner. You can then remove rotate the engine by hand severa l ti mes to verify either the camshaft timing sprockets, or the all components are properly timed and that the camshafts themse lves, depending on the particu- chain meshes smoothly. The f inal step shou ld be lar engine . For instance, on the M272 motor the to install the spark plugs and fire up the engine, timing chain on ly drives the intake cam, which allowing time for oil press ure to reac h the then drives the exhaust cam by means of gears. tensioner before accelerating. In th is case, the cams will have to be removed to access the tim ing chain. Drop the oil pan to 24 StarTuned
  • 25. A Mercedes-Benz should be true to its origins. So turn to the Mercedes-Benz Classic Center for Genuine Mercedes-Benz Classic Parts. Their experts have access to over 40,000 true-fitting Genuine Classic Parts of the highest quality, plus a 12-month limited warranty. They sell direct, ship direct and even assist In parts specification. Mercedes-Benz Classic Center When you want authentic parts, only the source will do. MBUSA.com/ClasslcCenter To speak with our Parts Experts, call our Parts Order Desk at 1-866-MB-CLASSIC (1-866-622-5277). Mercedes-Benz Classic Center USA, 9 Whatney, Irvine, CA 92618 Call or vi sit for additional details and a copy of the Limited Parts Warranty. <02008 Mercedes-Benz USA, LLC
  • 26. FEATURE ARTICLE / COLLISION REPAIR The Straight & Narrow When evaluating chassis integrity after collision damage you need to take the extra steps to verify straightness. The inherent value of a Mercedes-Benz vehicle definitely makes these extra steps worthwhile. the next step is to look for indirect Look at the collision industry Assessment or secondary damage that was statistics co mpiled in the last few ye ars an d you will notice an One of the first steps that is caused by this collision. Although increase in vehicles defined as a often overlooked and/or taken for we realize this is not always t he tot al loss by insurance companies . granted is the damage assess- case, it is often a good idea to The reason for this is multi- ment. This is more than just a visu- start pulling the frame in a linear fa ceted . Increases in the cost of al overview of the parts that will direction extending the body front pa rts, the short age of certified need to be replaced. A deeper to rear. Pulling fron t to rear wi ll body techs, and collision repair analysis should be incorporated "stretch" the chassis into a fac ility tooling/environmental into the assessment. Look at the straighter position . Obviously, compl iance costs have all con- point of impact and determine its with corners and angled frame tri buted to the overall price of a direction. You should think like a panels this will not always be the repa ir. Also, the vehicles them- detective at this point and try to best way to go, but it is a start. selves often contribute to the recreate the accident in your head . Sometimes it is better to pull the added cost. Exotic metals, con- It sounds like common sense, but framework at 90 degree angles to struction welding technology and this usually gives a good indication the panel's original location . This fastening techniques have all of what points you should start may take several steps as you required retooling and training, pulling from . Also, this may be a change the location and / or the wh ich adds to the overhead of any good way to gauge from what direction of the pull point to stay col lision repair shop . Mercedes- direction you should start pulling perpendicular to the panel you are Ben z vehicles, however, retain suf- once the chassis has been initially pulling. These are just some gen- fi cient value to justify the cost of straightened. eral guidelines rega rding frame repa iring most collision damage. Next, look for damage at the far- alignment meant to get you think- Reputable shops know the thest point from the impact. This ing about the next step, which is importance of returning the vehi- gives you the total surface area of developing a repair plan. cl e's structu ral integrity to its pre- all of the damaged panels . Even if collision state. When dealing with the damage in this area is minimal, Measuring Up frame damage, it's essential to it needs to be straightened. During the pulling process, it can be used An old adage says, " Before you restore the basic framework for as a gauge of the straightness of can go anywhere you have to proper chassis dynamics (such as the overall section. If the farthest know where you are ." The same suspension alignment) and future point of damage after pulling has can be said for frame straighten- crash-worthiness . You may ask now returned to its original shape, ing. This next step in the repair yourself, "When should I check you may want to start pulling from process involves measurin g chassis alignment?" and, "How another point. chassis alignment on a bench or can I do a better job of pulling that Back to assessing the damage, "jig" against Mercedes-Benz or chassis into alignment?" 26 StarTuned
  • 27. Vehicle Dody Informalion lUrudn .£j.nz. vthld15' 9o!1)'andBodyl,lat.rlallnlollna~on lor DodyslloP'. acclcl.nt UUUOI' alllllnlllram:.e camplnill Men;cdcs-Benz 230 ..... Home .~ '" ", ,~ '" '" '" ,,, '" • n •= ,,, M'" at.rlel, EIII/!pm.nI&TooI. OM :ldS!(I(II · >300rl/ """'It"'~l.ttcnltn •111&" ."1111,111 lie.! '" ~50 " /mm' !Cr.de wenltn • LUlI'ts"'m O Al~mlolUm . PI.a"~1 IB Oala ShH I230 Bodyfuluru Mod. rn hybf1 dbO"Ystructur, Intludlng hlgh-,ltenglh sin'. alum'num and mag onium • D. bCl'llbl, !font and lUI modules ma~. bod:)' repair easltr -----~-- -.. ~ Before you start the pulling process you need to know what met- als you are working with. Mercedes-Benz uses different metals with dif ferent strength levels to achieve structural strength and occupant safety. A visit to www.mbcollisioncenters .com and your membership gets you this important data. Car Bench is a Mercedes-Benz approved alignment jig for frame straightening. There are various models available, and by visiting www.carbenchna .com you can arrange bench rental and download measurement specifications.
  • 28. COLLISION REPAIR / SUB FRAME R&R !iil WISI.,RA no! " .. on, GJ@[gJ the frame until you match the measurements. These measure- ments are supplied by Mercedes- Benz through WIS-Net, wh ich you can access with a paid subscrip- tion to www.startekinfo .com. Aside from having the step-by- step procedure to rep lace interior body panels, it also conta ins measurements for K-point frame diagnostic procedures. If you have a hard time locating the K- point measurement spec ifica- tions, try entering a chass is num- ber or the entire VIN and look under group 40.30. Newer vehicles util ize a different procedure: measuring off of an alignment bench. Mercedes-Benz With a paid subscription to www.startekinfo.com. you can use has approved two bench manufac- WIS-Net to pull up the K-point measurement data. This infor- turers for chass is alignment, t he mation is only used for diagnostic purposes, particularly on Car Bench, and the Celette chassis older models built before the turn of the millennium. You can alignment bench. If you have invested in the Celette or Car use these measurement points to see how bad the damage is. Bench jig, you can access those the bench manufacturer's specifi- measurements from their web- cations . Here is where a hard sites. The Celette website is dec ision has to be made: Is the www.celette-us.com. On the home f rame damaged beyond repair? page, select the "Fixture bench No one wants to put in all the Setup Sheets" field, then select labor to get to this point and not your model chassis. There may be repair the vehicle. Tota ls should VIN number differences, so be have been weeded out during the sure to select the correct identifi- damage estimate. cation number. The Car Bench On earlier Mercedes-Benz mod- website is www.carbenchna.com. els (previous to the 210 chassis), From the home page, select chassis damage was measured "Support," then "Resources." Here is a Celette bench with off of a K-point. That is, a point From there, select the "+" symbol a 230 chassis set up for within the driveshaft tunnel that next to the heading "Datasheets," measurements and pulling. was hopefu lly the least likely to followed by the type of bench you The framework setup and are working with, the manufactur- be hit in an accident. The K-point procedures are all available er (Mercedes-Benz), model and is a diagnostic too l for body men on the website. Remember, chassis variant if applicable. to use to straighten frames. From this K-point you measure the dis- you can use higher strength Rental units are available from tance to all suspension pick-up steels to pull lower strength either manufacturer. These are the points and see if the chassis has steel, but you cannot reverse two chassis alignment jigs official- twisted. From here, you pull on the rule. ly approved by Mercedes-Benz . 28 StarTu ned
  • 29. They inherited our strongest genes. Not all remanufactured parts come from such hardy stock. re li abi lity. And they feature the same-as-new Replacement Genu ine Mercedes-Benz Remanufactured Parts strictly adhere Parts Limited Warranty. Access over 700 parts in 20 product to factory specifications - fo ll owing a uniform, precis ion lines for today's vehicles, and classics too. Offer your customers process. In fact, all wear and tear parts are replaced with OE affordable Genuine Mercedes-Benz Remanufactured Parts. pa rts - tested to OE specificatio ns - for higher qua lity and Visit mbwhelesaleparts.com or contact your dealer.
  • 30. COLLISION REPAIR / SUB FRAME R&R Bending To Your Will Once the chassis is on the bench Dor; . no. tr«I~~~!' ""'11' 1 01' s..o._~ .. ","", and the measurements have been taken, you can start pulling. Frame 1 Position modular members on indelC tiekl15 end 21 3 Mount Mu~I·Z on Side pbs (8). alaments M.Z 260 (arrow points towards the Iront) 2 Mount side Jibs (8) on modular members. straightening is an art developed 4 Insert cy~ndrical supports (10) Into Ml 260 (upper hOle) through experience, but there are some relatively new concerns with Mercedes-Benz designs and metal composition . In some cases, of course, the damage to a panel will be so great that straightening may not be the best option compared Fasten longiludln~1 portel member (9) at cylindrical supports with bolts M12 >:35 (11 2 and 8) 6m m ...- lI the rear lender Is removed, nLr~~r 'QnnQr l Insert spacer (dj (Shael lniCkness to rep lacement. In the case of high-strength steel, this becomes a requirement. High-boron steel is With your paid subscription to www.startekinfo.com. you can very difficult to reform after crash access step-by-step instructions for alignment bench assembly damage because it is so strong. and measurement procedures. You also are provided with Mercedes-Benz uses fou r grades replacement procedures for interior structural panels as well of steel: mild steel, high-strength as exterior body panels. steel , modern high-strength steel and final ly ultra high-strength virtually impossible to reform and strength steel and weld or bond steel. Mild stee l is much easier to will need to be replaced. When and rivet in the new sections. In pul l. The higher strength steels can damage is localized, it is much the case of the 215 chassis, you be pul led, but often return to the easier to cut out the damaged sec- have to be even more carefu l pre-pulled shape . Ultra high- tion and replace it. pulling panels since high-strength strength steel is heat formed, so Ultra-high strength steel is more steel and mild steel is mated with without extensive equipment it is widely used in new Mercedes- aluminum structural panels. On a Benz chassis such as the 204, 216 positive note, when pulling alu- and 251 , and to a lesser degree on minum Mercedes-Benz always the 164, 171, 211, 215 and 220 recommends replacement over chassis. The 216 chassis has repair work. incorporated even more higher- strength steels than other Mercedes-Benz models. When In Conclusion pulling ultra high-strength steel, it Your extensive experience as a will obviously react differently body man will serve you well while from modern high-strength, high- assessing the damage, measuring strength and mild steel. The key the alignment points and during point to remember is that you can the actual pulling procedure. Here is a frame attached to use higher-strength steels to pull Simply keep in mind the the bench. Points on the and align lower-strength steels, Mercedes-Benz recommended chassis can be measured but you cannot do the opposite for procedures outlined in WIS- from here, and you can start obvious reasons. You will simply Net and the knowledge of the var- the pulling process. On this deform the lower-strength steels ious metal compositions of the 230 chassis, you need to be in the process. Use ultra high- chassis you are working on should aware of the different metals strength to pull the chassis, then yield a structurally-sound and trou- and their relative strengths. cut out the sections of ultra high- ble free-repair. 30 St arTuned