TO OUR READERS:

IN THIS ISSUE

Welcome to STARTUNED, the magazine for independent service
technicians working on Mercedes-Benz vehicles. Your MercedesBenz dealer sponsors STARTUNED and provides the information
coming your way in each issue.
Mercedes-Benz wants to present the information you need to know
to diagnose and repair Mercedes-Benz vehicles accurately, quickly
and the first time; text, graphics, on-line and other technical
sources combine to make this possible.
Feature articles, derived from approved company sources, focus on
being useful and interesting.
Our digest of technical information can help you solve
unanticipated problems quickly and expertly.
We want STARTUNED to be both helpful and informative,
so please let us know just what kinds of features and other
diagnostic services you'd like to see in it. We'll continue to bring
you selected service bulletins from Mercedes-Benz and articles
covering the different systems on these vehicles.
Send your suggestions, questions or comments to us at:
STARTUNED
One Mercedes Drive
Montvale, New Jersey 07645
Phone: 1 201.263.7284
E-mail: Stefanie.A.Schweigler@mbusa.com

4

In order to maintain emissions
compliance, Mercedes-Benz engineers
have to control the temperature range
the engine will operate in and develop
engine management parameters within
this range . This may sound simple
enough, but how do you accomplish this
when the car might sit for an hour of
traffic on a hot summer day, or cruise at
highway speeds in the dead of winter?

12

Technical Advisor

Christopher M. Ayers, Jr.
cayers@automotivedatamedia.com

Tim Amun

Editorial Director

MERCEDES-BENZ CDI DIESELS: No MoRE
KNOCKING, SMOKING, OR STINKING

Unstable fossil-fuel markets, customer
environmental awareness, and
government regulations have all
contributed to automobile manufacturers
searching for the silver bullet fo!i mpg.
Mercedes-Benz has looked to its long
diesel engine history, and added a huge
dose of new technology.

STARTUNED is a publication of Mercedes-Benz USA, LLC ("MBUSA"). No part of this
magazine may be reproduced without the express written permission of MBUSA.
Editorial and Circulation Offices: 1348 River Road, Montague, NJ 07827.
CAUTION: Vehicle servicing performed by untrainedpersons could result in serious injury to
those persons or others. Information contained in this magazine is intended for use by trained,
professional auto repair technicians ONLY. This information is provided to inform these technicians
of conditions which may occur in some vehicles or to provide information which could assist them
in proper servicing of these vehicles. P
roperly trained technicians have the equipment, tools, safety
instructions, and know-how to perform repairs correctly and safely. If a condition is described, DO
NOT assume that a topic covered in these pages automatically applies to your vehicle or that your
vehicle has that condition. STARTUNED is aregistered trademark of MBUSA.

Group Publisher

NARROWING THE RANGE OF
TEMPERATURES WITH THE E-fHERMOSTAT

Donald Rotolo
Donald.Rotolo@mbusa.com

Bob Freudenberger
bfreud@automotivedatamedia.com

Contributing Editors
Bob Chabot
bchabot@automotivedatamedia.com
Michael Klaas
mklaas@automotivedatamedia.com
Tom Nash
tnash@automotivedatamedia.com
Frank Walker
fwalker@automotivedatamedia.com

22

MBUSA Technical Content Advisor

MEET THE CLA, MODEL SERIES

117

Big news from Mercedes-Benz! Not only
front wheel drive and MacPherson struts,
but also a host of other departures that
prove the superiority of the company's
forward-thinking engineering.

MBUSA Project Manager
Stefanie Schweigler
stefanie.a.schweigler@mbusa.com

Art Director & Circulation Mgr.
Christopher M. Ayers Ill
ayersc3@
automotivedatamedia.com
Cover photo:
2014 CLA250 (courtesy Mercedes-Benz}

Visit us at our web site
www.MBWbolesaleParts.com to view this issue and all past
issues of StarTuned, along with a wealth of information on
Genuine Mercedes-Benz Parts.
To locate a Mercedes-Benz dealer near you,
go to www.mbusa.com.

28

FWD & MACPHERSON STRUTS
CHANGE THE COLLISION REPAIR GAME

Many advanced steering, stability
control, and propulsion technologies in
the front-drive CLA depend upon precise
suspension geometry for proper vehicle
operation. Here are some front wheel
drive suspension basics for collision
repairers who will be working on this
history-making model.

When most of us think of technologica l
developments, we don't think about cooling
systems. We think about high-speed CAN data
buses th at al low the traction control system to
work with the electronic throttle to rein in a
vehicle. We may even think about fiber-optic
systems that carry music, mov ies, and media
for entertaining our passengers, and providing
nav igation. We think about electroni ca lly fueli njected hi gh-horsepower engi nes that sti 11 get 25
to 30 mpg.
Now think about a typica l ca r being driven in a
temperate cl imate that may sit for an hour in an
urban traffic jam on a 100 deg. F. day. Th is sa me
car may need to ca rr y its owner to work in si ngledigit temperatures on a February morn i ng. A car 's
cooli ng system does more than ju st prevent t he
engine from overh eating. It keeps it within the
temperature ran ge required to promote optimum
efficienc y and emi ssions control, and to allow long
life for mechanical components.
Engineer s design engines to work best within
a specific temperature range. The engine
management system uses coolant temperature
as a reference for controlling fuel deliver y and
ignition tim i ng. The pistons, r ings, va lve stems,

This is the e-thermostat location on a 221 chassis
with the V12 engine. It is buried under the
Secondary Air Pump motor and behind an idler
pulley for the drive belt. WIS can help you with
both testing and service procedures.
December 2013
5

bearings and other intern al engine parts will have
ex panded to the tolerances that wi ll maximize the
li fe of al l components. The cooling system's job is
to keep the eng i ne operating in that temperature
w indow as much as possible. Think of our example
of a ca r bei ng driven in traffic on a hot day. Most
of the ai rfl ow over the rad iator fin s would be
onl y what's ava ilable from the cool i ng fans. So,
the therm ostat opens all the way to allow the
maximum volume of coolant flow. On a cold day
at crui si ng speeds, the heat load is low, and so
is the temperature of t he coolant in t he rad iator.
The therm ostat will close as its element shrinks,
coolant fl ow is decreased. Thi s is how engine
temperatu re was maintained in its "Temperate
Zone" for decades.

1

c

• •
•
•
•

••

... ....
#

... -

•

•

#

•

I

"r"--~---~-~·--

•.-·

••
I

•

I

e:
I

I
I

WHAT'S AN E-THERMOSTAT'S PURPOSE?

To adhere to specific fu el mileage and efficiency
standards, engi nee rs needed t ighter control of
the engine's temperature. For the M272 engine,
Mercedes-Benz developed a more adva nced

..........

I

Right: In phase 3, the engine control unit starts to
energize the heater coil in the e-'stat and heated
coolant from th e engine block (passage 2) can
either flow through passage 3 (to the water pump),
or now to the radiator through passage # 1.
V1hldlK1•rcAt:•*ftUft'IOtr ~ l11H ll

Ill
W8

Cl'IH &ltmoot '"' CNt •

1 Ot' f"'*'Hl rtl'ICr!llM
.

#

•
......
I

3

· I.___ __ _ __ ___,

16U M ML. l$0 4MA.TIC • l7lte7 • A0 722t!le W7 C700 •

2.Stanau rth

*R'*MF
· ID g ic~1ooc.-nttt · I ~

© ~ · - · aD I ~ O;;; ~ F•;•""°'

vau.:,°'

P1~11or2

BooQMM

~ ~~=:::~~~------------~
I24.9.09

I

EPC

Use www.startekinfo.com to access WIS. This will give you all the steps needed to service the
e-thermostat. Here, we have looked up the procedure on a 164 chassis M -Class with the 272 engine.
6

Mercedes-Benz

StarTuned

·~

~

1

1 ln~eit~not ui ~
~~·
i' - @I ~l·-f
...,
- E:J E) CJll
GT 0 LJ
Q

-

thermostat that can control engine temperature
accurately in mu ltiple situations. It still functions
like a traditional thermostat with an ex pand i ng/
contracting element that opens and closes
according to coolant temperature, but it has three
disk s (meaning the thin, round meta l pl ates th at
altern ately cover and uncover coolant passages)
instead of the normal single disk to graduall y step
coolant fl ow, and a computer-controlled heating
element. The three disk s prov ide four di fferent
stages in openi ng the thermostat. Each stage
regulates the coolant tlow to match the cooling
prov ided by the radiator and the needs of the
engine. A ny thermostat, even the "e-'stat," has a
full y closed position when the engine is cold to
build up coolant heat quick ly. Rapidly reaching
normal operati ng temperature allows cr itical
mechanica l components to ex pand to th eir idea l
work i ng shape as soon as possible, and speeds the
transition to closed-loop operation.

You can measure the resistance of the heating
Think of the e-therm ostat as hav ing one si ngle
element in the e-thermostat to see if it's okay.
A good one will have about 14.7 to 15.0 ohms at
upper di sk and two staggered lower disks. The
room temperature. The electrical connection is
upper disk di rects coolant flow to the rad iator, and
a little difficult to get to, so you may want to put
the lower disks can either al low coolant to be spl it
your test leads across one of the wires that share
between the eng ine and the radiator, or totally
the po wer supply and the pin on the ME control
block flow to the engine forci ng all of the coolant
unit that g rounds it.
flow through the
radiator. During a
••
cold start, both the
'
upper disk and one
of the lower di sks
total ly block coolant
fl ow allowing the
engine to bu i Id heat
rapid ly. The heat of
.,,.
"'
the engi ne coolant
opens the fi rst
stage supply i ng
the heater core in
the cabin . In the
th i rel stage, the
computer controls
the current flow i ng
,.
"
th rough a heater
Here we are looking at the electrical control of the e-thermostat. The upper blue
element inside the
trace is the voltage signal. The lower brown trace is the amperage draw. Soon after
body of the e-'stat.
a hot restart, the ME grounds the element for a fe w seconds and we can measure
This assistance
th e amperage dra w. If amperage draw is too lo w or too hig h, the e-thermostat has
occurs on both a
probably failed.
Mercedes-Benz Sta rTuned
8

..

Cl(

..

..

...

...

...

.

..

hot resta r t where the eng i ne temperature reads
over 208 deg. F. (98 deg. C), or after a cold start
where t he engi ne temperature is about 82 deg. F.
(28 deg. C).

WHEN THE

ME IS IN

COMMAND

The ME control un it (aka the PCM for Powertrain
Control Module, or engine management computer)
can r egulate the temperature bet ween 185 deg.
F. (85 deg. C) to 22 1 deg. F. (105 deg. C) wh ile the
engine is runn in g. Above these temperatures, the
ME com ma nd s t he thermostat to block coolan t
flow back into the engine, directing all coo lant
flow to the radiator for maximum cool i ng. ts you
can see, wi th cooling temperatures reaching above
221 deg. F. (105 deg. C), and the boiling poi nt of
water being 212 deg. F. (100 deg. C), it is critica l
that the mixture of Mercedes-Ben z extended l ife

® Me1~edes-Benz
A~ticorrosion/
Antifreeze AGENT
Pro1ec1i
aqo Ir

tadlator ano
Can,,tezJno ano raJ engine lrom corrosion
lat Se~~:eo~ lo MerceJ::.Jha boiling polnl.
rooucts sheet N Specifications
anz
o. 325. 0
P
111 Hurnbtr

!~ 1030004

""'-c;

""°"·l~LllRES

~°'"'""' ""'-lOWto '--..uo
. ......

It makes no sense to use anything but genuine
Mercedes-Benz antifreeze for cooling system
service. The current blue-dyed formula carries the
part number BO 1 03 0004, which is also designated
as G48. It only comes full-strength, not pre-diluted.

coolant and water be i n the proper dilution ratio
to transpor t Btus efficien tly. The fundamental
functions of the cooling sys tem must be worki ng
properl y for the e-thermostat system to be able to
do its job. The water pump must stil l be capable of
provid i ng sufficient flow, and there cannot be any
air in the system. When diagnosing and se r vici ng
these systems, do not j um p to testing this new
technology until you have done some basic checks,
such as pressure testing.
The e-thermostat gets its voltage supply from
power dist ribution compone nts such as the front
SAM. The ME controls t he ground with a pulsewidth modulated signal. It determines how much
cu rrent should fl ow t hrough the heat ing element
usi ng coolant temperature, engine speed, engine
load, and vehicle speed as references. You ca n
mon itor the vo ltage signal and curr ent flow directl y,
or you can monitor e-t hermostat operation through
Xentry software. vlhile it is possible to test the
element at t he therm ostat itself, in most instances
it is difficu lt to get to and may require tha t some
components to be removed . What may be easier is
to measure the resistance, voltage and current at
the ME. Looking at a wiring diagram available on
www.startek info.com, you can identify the grou nd
pi n locat ion at the ME and put your other lead on
one of the shared power suppl y wires.

STAGES
The ME controls thee-t hermostat in three
stages. It ca n leave t he heat ing element alone by
not provid ing any g round. Without a ground, the
circuit is incomplete -- there is no current fl ow and
therefore no e-thermostat activ ity. Or, the ME can
pulse the ground thereby heating up the element
to a specific temperature and maintaining th at
temperature. It can also ful ly ground the element
to allow maximum current fl ow, thus generating
the max imum heat the element is capable of. You
ca n monitor th is ci rcuit for vol tage and amperage.
As the wi rin g diagram shows, you shou ld find
batter y vol tage on t he circu it when the ME is
not g rounding the element. When the ME star ts
to ope rate thee-therm ostat, you may see your
read ing go directly to ground, or find a pulsew idth modu lated sig nal. Hemember, the pulsew idth moclulated signal holds thee-thermostat
December 20 13

9

in a static position to regulate the coolant tlow
between 185 deg. F. (85 deg. C) and 221 deg. F.
(105 deg. C).
I f you measure the current tlow w hile the
e-thermostat is being grou nded, you shou Id see
about 7/ I Oths of an amp (0.7A). I f you measu re
directly, t he meter wi ll probably average the
signal over time so you w ill see less amperage
wh ile the signal is pulse-width modulated . You
w i II have to wait for the eng ine to run long enough
to full y ground thee-therm ostat to measure the
amp draw accurately. If you use a scope w ith
an i nduct ive m illiamp probe, you can monitor
both the voltage and amperage at the same time.
A lmost immediately afrer a hot resta r t, the ME
operates thee-thermostat for approximately six
second s, du rin g w hich time you ca n eas il y r ead
the voltage and amperage. I f you are usin g Xentry
software to v iew the computer 's management
actions, it w ill g ive you a data PIO to evaluate the
comma nd s to thee-thermostat.

IT'S STILL A COOLING SYSTEM
As mentioned earli er, ever y other aspect of t he
coolin g system must be function ing properly for
the e-thermostat to be able to do its important job.

~·

If you're doi ng a flush and refill as maintenance,
or w henever you've done any major cool ing system
worl< that required dra i ning, it's recommended
th at you use coola nt exc hange equ ipment. Not
only is it a lot fa ster and neater, it does a much
better j ob of completely fl ushing the ent ire system,
el iminates trapped ai r that can cause various
troubles, ensures a complete fill, and even helps
you find lea ks. By the way, thee-thermostat has
a check ba ll to al low ai r to pass through it during
th e fillin g.

Of course, to keep t he ca rs i n you r care troublefree, always follow the cool i ng system maintenance
i nter vals stated i n the Owners' Manual or on WIS
to the letter, and use on ly genuine Mercedes-Benz
antifreeze for top-ups and refi lls.
Know in g how a system functions and w hat you
can do to ser v ice it is what keeps your customers
comin g back. By purchasing genu i ne MercedesBenz pa rts from your dealer you have a partner i n
the ma intenance of your customers' veh icles who
not onl y suppl ies properly-engi neered parts, but
also offers the best wa r ranty in the i ndustry. Who
would n't wa nt a partner li ke t hat? I

:::- ·
1

.J !p91:1Ip EM1f!t

1 J

1

/>

eltlOuaoout

l!W!f1'UlpQ• Q?

'"9' '~'lt'"t:Y-'C"
S:::

.,

A 1nlOOOlU

O.UtM"IAI

r ~br. A2122'000.&tS

J IPPI p10 prn raornzt Jt'l>S1iH

~·
l)MlfnnfMQ l!QQWHfremDt

r

50

ACIDD9Hl20)

• Dflt Wls...DIC

r

60

A mlDJ CO.,

. CAs&rl
1lfJtN)$'1AJTOTM«:OCA!Z

SC&)6~.. . .

I- - - - r

60

A mJOJOUO

00 1

~ fPM]IQ fM!!t'.!OOW21IpDMtOZ
· ~

_
CIO I

THJtNZTAT 10 1lMM: ~

1-- ----~ !0C?!! EC2!!! ED'Z'f

r
r

,.

r

IO

'.Xrn-"'J.! rrmo1

"'

090

.J !5!0l!I9 Enzr1 )9Ct".tOl l1PN 0'2

.......

o~

"°""""

..J ~

l:l.J!.la_
HQOOOQ000 111,

HUAlOIUlAA 80l.1

00)

nOHOST.t.T fO BCH;CA2 Mfill.U

r

.,

......

.J e"?fllsf11-• w u uraprr

(I?

TtOMOS'TATTO TMt«; CJ«.

IO-----J &r?! [t90f~t )9!?!.11Hfr;:mQ1
r
L:io
• 2n mo:n 1
VAl'rt
C'l'l.HXJl tUD, LD'l u:AA

.,,~

.:J

Use Mercedes-Benz EPC to assist you in identifying the proper part. While you should always trust the
knowledge of the parts man at your local dealer, EPC will help you identify other parts you may want to
replace during the job, such as a new electrical connector if the old one was damaged.
10

Mercedes-Benz

StarTu ned

Mercedes-Benz CDI Diesels
No More Knocking, Smoking, or Stinking

12

Mercedes-Benz

StarTuned

Unstable fossjj-fuel markets, customer envjronmental awareness, and
government regulaUons have all contrjbuted to automobile manufacturers
sear ching for the silver bullet for mpg. Mercedes-Benz has looked to Us long
djesel engjne hjstory, and added a huge dose of new technology.

Ask powertrain engineers and they wi ll all
tel l you thei r ultimate goa l is " the free lunch." Of
course, Ii ke the physici sts' Absolute Zero, that's
not rea ll y attainable, but it at least provides a
clea r direction. The goa l of an engin eer is to
optimi ze an intern al combustion engine's output
in order to produce max imum power while usin g
the mini mum amount of fuel. Approaches such
as turbocharging, variable va lve timing and lift,
direct fuel injection, etc. all contribute to this
mai n objecti ve.)
There's a concept that goes even furth er,
however: compression ignition. Diesels have
always sq ueezed more u seful work out of a
ga llon of fuel th an gasoline-burning engines,
and w ith Mercedes-Ben z's application of
adva nced tech no logy t hei r inherent draw backs
in term s of noise, smel l, emi ss ion s, cold sta rtin g,
and lacklu ster perform ance have all been pretty
much elimin ated. This ar t icle is intended to
help you keep up w ith t h is tech nology so that
yo u'll have a better understanding of the ser v ice
req uirements invol ved.

SINCE 1936
Mercedes-Benz has always felt that the diesel
engi ne has tremendous adva ntages when it
comes to incr easing fuel economy and reducing
harmful emi ss ions, although on ly the former was
germ ane in 1936 when the compa ny introduced
the 2600, the world's first diesel passenger ca r.
It has successfull y sold diesels to the A mer ican
pub! ic for decades. With the modern push for fu el
effi ciency and clean ex haust, Mercedes-Benz has
pract ica ll y reinvented the compression ignition
engine. Elect ron ical I y-control led high-pressure
di rect injection and an after-combustion cataly tic
system are just t wo of its prominent advances.

December 2013

13

But revolutionary
engineerin g
improvements rarely
come w ithout additional
levels of techn ical
complex ity, which makes
our job of keeping
ever ythin g operatin g
properl y challeng ing.
A/e believe, however,
that you will find that
your ex perience w ith the
electron ic management
systems of gasolineburning eng ines w ill be
ver y helpful.

MAJOR PSI

With a paid subscription to www.startekinfo.com, y ou can access function
Th e Mercedes-Ben z
diagrams in the ETM section. These let you know wha t sensors and control
CDl (Common rail Direct
units ar e involved in the system you are working on. This is a function
Injection) system has
diagram of the smooth-running system on the 642 diesel engine. The
an elect r ic fu el pump
CD/ control unit looks at all of these components to mitigate crankshaft
that supplies relati vely
fluc tuations through individual cylinder injection control.
low pressure, but h ig h
volume, to the mechanica l
high-pressure pump that's driven by a camshaft.
The 5,000 to 30,000 psi (!) generated is routed
th rou g h a common rai I t hat bran ches to the
indi vidual injectors, so it 's simi lar to a typica l
port-ty pe gasoline EFJ albeit at up to 600 times
the press ure. The injectors are opened when the
CDI control unit sees fit, aga in si milar to EFI.

As in any modern eng ine, the control unit gets
signals from both crankshaft and camshaft posit ion
sensors to determin e where the eng ine is in its
four-stroke cycle (many oth er inputs are invol ved
in the grand scheme of thin gs , too, of course), thus
when to fire each injector, but it's relieved of the
duty of cont rolling an ig nition system. The serious
pressure in this system not onl y g reat ly enh ances
fuel atomi za tion , it also makes th e effi cient direc t
inject ion feature work better.
Once diesel combustion ha s taken place and t he
last possible ounce of power has been ex tracted
fro m the air/ fuel charge, Mercedes-Benz made sure
the ex haust comes out squeak y clean by mea ns of
the Selecti ve Catalyst Reduction system (SC R) th at
aids in th e continued co mbustion of any excess
14

Mercedes-Benz

StarTuned

It was 77 year s ago when Mercedes-Benz
introduced the world's first diesel-powered
passenger car, the 2600.
fuel tha t did not burn i n the combust ion chamber.
Thi s utili zes urea i njecti on -- a chem ical add it ive,
commercially called Ad Blue® Diesel Exhaust Fluid
(DEF), is sprayed i nto the SC R system. This type of
system has been around for yea rs in t he Eu ropea n
trucl<ing industry, so is not a new, unt ried
concept. It's needed to make the engi ne emi ssionscompliant, and be full y functional in order for t he
eng ine to be allowed to r un.
An easil y-accessible Ad Blue® DEF tan k is
mounted i n th e vehicle, and each gallon lasts at

least 2,500 m iles . A level sensor lets the control
un it know how much flu id is i n the ta nk. lf the
flu id drops below a specified level, a message w ill
appea r in the i nst r ument cluster ("C heck Ad Blue®
/
Check Diesel Ex haust Flu id (DEF)"). I f t he veh icle
is driven for a certai n amount of t i me with the
wa rn i ng i ll umin ated, a gong w il l be sou nded. The
number of gongs sounded starts at someth ing li ke
21, dependi ng on the model. If t he level is al lowed
to drop even fu rther, the nu mber of gongs w i l l go
dow n also reflec ti ng the nu mber of engi ne sta r ts
permi tted. Once it reaches zero, the control un it
wi ll either put t he engi ne into id le mode, or prevent
it from sta rt i ng, dependi ng on the model. Add i ng a
ga l lon of AdBlue® w ill get thi ngs going aga in .

THE PLAYERS

Here's what the ADBlue® DEF tank filler cap looks
like. The fluid level is continuously monitored to
make sure there is enough. When it gets low, a
message will appear in the instrument cluster,
then t here will be a warning gong.

We al ready know the CDI control unit completes
the ci rcuit to the fu el i njector s. We also lrn ow that
the control unit rece ives cran k and ca m position
sensor signals so it ca n determine when to fi re t he
injec tors. But, as mentioned above, t here are many
ot her sensors and solenoids that help ma nage al l
that fue l press u re. Si nce t ime is of t he essence in

Test of high-pressure regulation
, Actual values
.

I"""

600

624

361

1338
-10s

_j_

Os

Rail pressure regulation : Rail pressure regulation Ilia press ure regulator vallle
Pressure regul ator valve and quantity control valve (mixed-fuel operation)
- - - ------- -- - - - ---- - -- - - - -- - - --- -- -- ---- - --- -- - -- - -- - - - ---- -- - - - --- - - - ------------~

Rail pres sure regulation Via quantrty control valve
--- ---- -- ---- - - ------- - - - ---- ------ -- --- - --- ------ --- - - - - ----- - - - - ----- - -- -- ------~

Rarl pressure regul ation via pressure regulator valve

With a XENTRY system you can graphically display the fuel rail pressure as picked up by the fuel rail high
pressure sensor. Here, we see the thick black line indicating the increase in psi as the engine is cranked
and started (then immediately shut off). This can help in the diag nosis of a no- or hard-start condition.
December 2013

15

a high-pressure direct fuel inject ion system, more
is needed t han just increased inj ector on-t i me to
add enough fu el under acceleration. The pressure
itsel f is increased in order to get more fu el into
the combustion chamber under high demand. This
is one in sta nce where diesel eng ines di ffer from
their gasoline counterparts. With gasol i ne fuel
i njection, injector pul se w idth is increased to meet
the demands of acceleration, but system pressure
stays pretty much con stant.
COi controls t he amou nt of pressure in t he fuel
system with a combination of a Quantity Cont rol
valve (mounted on the high-pressure pu mp) and
t he Pressure Control valve mou nted on t he fuel
r ail. Both receive pulse-w idth modulated signals
from the COi unit.
The COi cont rol unit needs to be aware of the
actual pressure i n the fuel rail (also ca l led a

" mani fold ") i n ord er to ca lcu late pu lse w idth and
pressure requ irements. Lt gets t his i nformation
via a high-pressure sensor mounted on t he ra il.
As w ith any other diesel, the high compress ion
generated by the engi ne starts t he combust ion
process. On ver y cold days, it is somet i mes
difficult to get th e fire star ted. In older desig ns,
there was a pre-cha mber w ith a glow plug
installed. When the ig nition key was t urned on,
the glow plug heat i ng element was suppl ied with
electri c current. Th is wou Id heat t he fuel as it
entered the chamber, maki ng it easier to ignite.
Wit h COi, penci l-t ype glow plugs are mou nted
directl y i nside the co mbusti on chamber for preheati ng. A separate glow plug cont rol un it supplies
the necessa r y am perage wi th t he igni tion key
on and duri ng the wa rm-up phase to i ncrease
effi ciency. The glow pl ug control unit takes its
orders f rom the CDI control unit.

Here's th e fuel rail of th e new four-cylinder Mercedes-Benz diesel eng ine that 's gaining so much notoriety.
Metal lin es car ry the pressur ized fuel to the individual injectors. The fuel volume is very small, so even a
small leak will not allow pressure to build. This can lead to a hard- or no-start condition.
16

Mercedes-Benz

Sta rTuned

INJECTION ACTUALITIES
When we th in k of traditional gasol i ne EFI, we
t hin k of a computer energizing a solenoid that
allows pressurized gasoline to pass t hrough a
nozz le. vVith a high-press ure diesel fu el system
capable of produci ng 30,000 ps i or mor e, it may
seem that it wou ld be virtuall y impossible to
electrica ll y open an i nj ec tor whose pi ntle has
t hat mu ch force bea rin g on it. Engineeri ng
injectors that could do j ust that dependably was
one of COi's break throughs. Depend ing on the
year, model, and countr y of sa le, eit her t he Piezo
type or electric soleno id ty pe has been used.
Rega rdless, t he t raditional diesel's rattle and
k nock are practica lly eli m inated by up to seven
injection events occurri ng for each power st roke.
It's not j ust one big blast any more, but a relati vely
slow, con trol led burn .
Bein g a seq uent iall y-fi r ed injec ti on system, CD I
is prone to some of the sa me dr ivability issues
usually associated w ith gasol i ne SEF I. Older diesel
i njection systems ty pica ll y had a mechanical ly
or electrically-cont rolled pum p. A rack inside t he
i njection pump would be moved to provide more
or less fuel to all of the cy linders. If you had an
i ndi v idual cyli nder misfire, or " nailing," it was
due to eit her the injector itself, or to an eng i ne
mechan ica l problem, such as a bad va lve .

With com mon-rai l, each cyli nder is i ndi v idual ly
control led . CDI has the sensitivity to continuously
mon itor and adj ust inj ector tlow rates to match the
needs of i nd iv idual cylinders. The CDl unit needs
to k now the flow rate of any injector t hat is bei ng
replaced. T his in for mation is entered i nto t he CDI
unit t hrough the SDS/XENTRY software. As the
i njector wears, t he flow rate may change over
t i me. The CDI uni t also monitors t hese cha nges
and per for ms "adaptat ions" accordingly. These
adaptatio ns need to be cleared after replaci ng
i njec tors or otherw ise serv ici ng the system so the
CDI does not inject fuel usi ng i n for mation from
the old i njectors. These adaptations can be v iewed
and reset wit h your SDS XENTRY system.
/

WE NEED FEEDBACK
Just like modern gasol i ne i njecti on systems,
t here needs to be a sensor tha t mon itors t he
effectiveness of fu el contro l. The CDI un it is
always ask i ng itself, "Am I inject ing too much or
too little fuel for complete combu st ion?" To get
an accurate answer to that quest ion, t he CDl unit
uses a w ide-band oxygen sensor -- t he gasoline
engi ne equiva lent would be cal led an ai1jfuel ratio
sensor. These sensors have a si x-pi n connector
and use a millia mp sig nal to indicate a r ich or
lea n mi xture to the CDJ control unit. They ar e
capable of measuring a wider r ange of m ix t ure
ratios th an cou ld a traditional zirconium oxygen
sensor. Hav i ng a good understand i ng of modern
Mercedes-Benz diesel fu el i njecti on systems wi ll
allow you to perform proper maintenance and
more acc urate diagnosis of any complai nts. Your
local Mercedes-Benz deale r 's pa r ts depart ment
is a part ner i n this process, and w ill support you
in mak in g sure you have t he k nowledge and t he
qua l it y parts needed to se rve your customers in
t he most profess iona l manner possible. I

Left: Between the fuel pump and the high-pressure
pump, there is a fuel filter with a "water in fuel"
sensor. When the filter's water separator is more
than half full of H20, a warning light in the cluster
will turn on. This filter needs to be replaced at
the specific intervals outlined in the maintenance
booklet, but may need to be replaced more
often depending on the quality of the diesel fuel
available to your customers.
December 2013

17

Reman Airmatic Strut

MSRP*

New MSRP*

% Savings

A219 320 1113 80

$1,140.00

$928.00

-19%

A219 320 1213 80

$ 1,140.00

$928.00

-19%

A211 490 0819 80

$1,720.00

$890.00

-48%

A211 490 0919 80

$ 1,180.00

$581.00

-51 %

A642 010 4006 80

S3 0 ,170.00

$ 13,830.00

Genuine Mercedes-Benz Reman Parts:
Value, Quality and Reliability
All Genuine Mercedes-Benz Remanufactured
parts are renewed and produced to the exact
Mercedes-Benz specifications, ensuring
optimal performance at significant savings.

~ - Cl~

Ou••.&G..10)46h.tf.CM. ~

Mercedes-Benz G

Remanufactured p rt

For the complete portfolio of Remanufactured
products, please contact your authorized
Mercedes-Benz Dealer or visit
www.mbwholesaleparts.com

.
enwne

ll~IDiL

@ Mercedes-Benz
•Excludes core charge.

Let's just hit thi s head-on: In spite of w hat some
snide automoti ve journa l ists have said comparing
the Amer ican i ntroduction of a Mercedes-Benz
FWD platform to "the fall of Western Civ ili zat ion,"
or "the end of life as we know it," it is anyt hin g
but. Instead, it represents an i mportant, positi ve
departure t hat w i ll allow the St uttga r t company
to weather the pred ictecl tu rm oi I of extreme fuel
economy ancl emissions regulat ions, ancl , w ith it 's
high-value pricing, attract anoth er whole level of
buyers to the brand , whi ch ca n' t do any thing but
help Mercedes-Ben z ser v ice special ists l i ke you.
The FW D CLA belongs to the company's "New
Generation Compact Ca rs" fami ly, whi ch w ill
go a long way i n defining its futu re, here and
elsewhere. The Model Seri es 117 is a fou r-cloor
premium coupe in th e compact segment, bu i lt
on the current A-Class and B-C lass moclels solcl
elsew here. Innovations abound in thi s class that
i mprove energy efficienc y ancl further reduces
emissions, besides offering unprecedented safety
ancl comfor t in a car at thi s price point.
Wh ile you probabl y won' t be seeing these cars
in you r bays for some yea rs, we at StarTunecl
bel ieve you shoulcl have a clear iclea of w hat your
future holds, so here we're going to lay out the
amazi ng array of features the CLA presents (well ,
ma ny of the important ones, at least).

FOUR -- WHO NEEDS MORE?
The AMC CLA 45 versi on , at $ 17,550 more than
the CLA 25 0, is bil lecl as hav ing the most powerful
production fou r-cyl i nder in the world w ith 355 hp
ancl 332 ft. lbs of twist. But you'll be seeing a lot
more of the CLA 250, which is no slouch. With
208 hp and 258 ft. lbs. of torque, it produces a nice
combin ation of 0-60 in less than seven seconds,
along with 26 city/38 hi ghway mpg -- incredible
for a 2L in a 3,300 lb. car.
Th is feat is achieved by means of the fol lowi ng
engine character istics (among other thin gs):
• Low i nterna l fr iction
• Gasol ine direct injection
• Piezo injectors for multiple fuel injection events
• Tw in-pipe/ scroll turbochargin g w ith up to 27
psi (1.8 bar) of boost
• Highl y-evolvecl intake ancl ex haust cam shaft
dy namic t i ming adj ustment
• Dem and-controllecl multi-spark ig nition
• Opt i mi zed thermal management
• ECO star tjstop function
•Opt i mi zed regulation of the oil and cooling
ci rcuit pumps

DRAG

& MULTI-SQUIRT & SPARK

Mercedes-Benz was the first automaker to use
cast-in si licon-alu minum cylinder sleeves w ith a
low-friction surface that allows piston-rin g spr ing
tension to be reduced by 50 perce nt. In the CLA's
case, t he cyl inder sleeves get a "NANOSLIDE"
coating to optim i ze both the production process
and friction characteri stics.
Other mechan ica l eng ine features include forged
pistons des igned to w it hstand ign it ion pressure
loads of 2, 100 psi (140 bar), a forged cra nk shaft
w ith eight coun ter weights, bearing caps made
of cast iron with nodu lar graphite, and a v iscous
vibration cl amper.

Don't be shocked to see that four-cylinder engin e
in there transversely. It 's an essential element
of Mercedes-Benz's "New Generation Compact
Cars" fam ily. Shown is an A-Class, which has been
successful in other markets.

Another first for the company was the ori gin al
gasol i ne direct inj ect ion system on the legendar y
1
954 300S L Gull w i ng. The t hi rd generation
of modern GDI uses piezo-cerami c cr ys talline
elements i n the inj ectors. Replacin g mechanical
solenoids, the piezo cr ys tal changes shape
December 2013

21

in stantl y when electrical current is applied,
wh ich makes it possible to progra m several small
injection events per cycle. The first occurs as
t he piston is descending on the intake stroke.
Depend i ng on speed , load, and temperature
conditions, another i njection (or two) takes place
durin g the compression stroke before ignition,
for mi ng a strati fi ed m ix ture. A fourth inj ection
can stabili ze combustion if it's needed. System
pressure, by the way, is up to 2,840 psi (190 bar),
i n the range of a pre-common ra il diesel.

• Electronic accelerator
• ECO startjstop function
• Stepless adjustment of i ntake and
exhaust ca mshaft tim i ng
• Turbo boost pressure
• Torque i nterface to ESP, tra nsmi ssion,
and air condition i ng
• Alternator i nterface

Coord i nated w ith th at sophisticated meteri ng
of gasoline is mu lti-spark ignition. After the first
spark, the syste m ca n recha rge and deliver up to
three more sparks w ithin a single millisecond,
creatin g a gas plasma w ith more expansion than
convent iona l ignition wou ld allow. The ti me lapse
between spark s is adjustable, so combustion
duration ca n actuall y be controlled, r esulting i n
two percent better fuel economy, and a tota l of four
percent improvement in combination wi t h di rect
fuel injection.
Of course, t hese prec ise fu nctions are
orchestrated by t he M E-S FI control un it, wh ich
is attached to the ai r Fi lter housing for cool ing.
It does a lot more than that, t hough, i ncluding
management of:
• Cyli nder-selecti ve, adaptive knock control

22

Mercedes-Benz

StarTuned

Here's the mighty AMG version of the CLA 2L
engine. At 355 hp and 332 ft. lbs. of torque, it's the
most powerful production four-cylinder in the world.

• Thermal management for shortening
warm-u p phase
• Engine oi l pum p control
• Ex hau st fl ap control
• Diagnosis and fault storage
• Drive authori zation system and immobili zer

If the M E detects a mechanical fault i n the
electronic accelerator throttle actuator, the fu el
i njectors are partia lly shut off in order to restr ict
engi ne speed to 1400 r pm at idle, and 1800
r pm whi le dri vi ng. Ano ther safety-r elated job
is shutting dow n t he fu el pump in the absence
of an engine speed signal, or if a crash signal
is received indirect ly v ia the chassis CA , or
direct ly from t he supplemental rest ra i nt system
control uni t. In addition , t he injectors are briefl y
actuated to depr ess u r ize t he fu el system.

CURRENT MANAGEMENT
The electrical system batter y (GI) is located in
the driver 's side of the engine compartment. A n
add itional batter y (G l/ 13) for the ECO star t;s top
fun ct ion is i nsta lled in the front passenger footwell.

The bottom end looks indestructible. The crank,
rods, and pistons are all forged.

The energy managem ent system ensu res that
the engine can be started and that al l electrica l
consumers receive a reli able power suppl y. Th is is
ach ieved th rou gh the major assembly coordinator
and on-board electrical system management
subsystems. The major assemb ly coordinator is

A low-pressure pump moves gasoline from the 50L high-density polyethy lene tank (six layers with a block
layer made of ethylene vinyl alcohol to prevent hydrocarbon evaporation) to the high-pressure pump,
which can generate an impressive 2,840 psi (190 bar).
December 2013

23

for usage with the startjstop func tion. When
thi s function is acti ve (engine off), the electric
auxiliary oil pump supplies the shift elements and
actuator s w ith oil.

integrated into the ME and forms the interface
of the on-board electrical system management to
the alternator. T he ME communica tes with the
altern ator v ia the powertra in LIN (LI N C1). The
major assembly coord inator regu Iates the power
output of the alternator i n accordance with the
instructions of the on-board electrica l system
management, taking engi ne load into account.

Automatica ll y controlled all-w heel drive
(4M AT IC) is optional, w ith power sent to a mu ltidisk clu tch i n t he rear ax le differential.

ELECTRICALLY-POWERED STEERING
Yet another big advance is the electric power
steerin g, wh ich consists of a rack-a nd-pi nion steeri ng
gear, a torque sensor, an actuator motor, and a
control unit. The steering assista nce is transm itted

The on-boa rd electrical system diagnosis
function provides precise analysis of causes i n
the event of complaints. The last 100 dri vi ng and
idle cycles are stored with im portant in form ation.
Th is can be read out using Xentry. In
addition, the diagnosis function now
makes it possible to r ead the no-load
cu rrent curve for the most recent hours
and display it graph ica lly.

The lG-DCT transaxle is a sevenspeed, dual-clutch, three-shaft unit.
Clutching and gear changes are
rapid with no rpm flare.

TRANS
The adoption of FWD and
the ti ghtened requirements for
performance and fuel efficiency
r esulted in a trul y unique new
transax le. The 7G-DCT is a 7-speed
dual-clutch, three-shaft transmi ssion
unit. It consists of two subtransmissions each w ith its own clutch.
Clutch operation and gear changes
occur rapidly w ithout interruption of
tractive power for improved effi ciency
and sport y vehicle dynamics.
A few more important features of t he
7G-DCT:
• Wet, hydrau lica l ly-operated dual
clutches
• One oil circuit for
hydraul ic control
and lubrication of
the gear set
• Integrated electric
aux iliary oil pump
• Integr ated shiftby-w i re
Cooling is hand led
by an ac ti ve oil system.
It is also suitable
24

Mercedes-Benz

StarTuned

At a Glance ...

MSRP
Fuel Economy
Engine
Performance
0-60 (sec.)

CLA250
$29,900
City: 26MPG
Highway: 38MPG
Combined: 30MPG

CLA 250 4MATIC
$3 1,900

TBA

2.0L lnline
4-Cylinder Turbocharged
208 HP
258 lb-ft torqu

2.0L lnline
4-Cylinder Turbocharged
208 HP
258 lb-ft torque

6.9

6.8 (est.)

by the motor to the rack-and-pinion to boost the
steering moment applied by the dri ver. Compared
to hydraulic power steering, electric steering force
assistance offers the follow ing advan tages:

• Electron ic brake fo rce distribution (EBD)
• Anti-lock braking system (ABS)
• Acceleration skid control (ASR), electronic
traction system (ETS)

•Im proved steering feel

• Brake Ass ist (BAS)

• Fuel sav ings

• Dry braki ng

• No power steerin g fluid req uired
• Compact design

• Precha rg i ng, depending on acceler ator
pedal actuation

• Speed-dependent steering force assistance

• Prechargin g, depend ing on lateral acceleration

• Ass isted steerin g return

• Standstill coordinator (SSK)

•Diagnosis capabil ity

• System fault d isplay

The brake and engi ne intervent ion function s of
ESP, which are intended to stabi li ze the vehicle, have
been supplemented by steeri ng torque intervention.
This additional steerin g torqu e is prov ided in the
form of electri c steerin g force assistance.

TONS OF BRAKE FEATURES
Mercedes-Benz has spared no effort to make
su re the CLA has an i ntegrated bra ke system
that's more than a match fo r the compet ition where
high-technology is concern ed. For exa mple, ABR
(Adaptive Brak e) assists the driver in da ngerous
situation s which occur suddenly. Th e fa mili ar
system has been adapted to t he new model ser ies
and consists of the fo llow ing subfuncti ons:

• ESP dynam ic cornering assistant
There's even a n electric par king brake, wh ich
is identical to t hat fou nd on models R231 (SL)
and R172 (SLK). It acts on the rear w heels by
makin g use of spec ial elect r ically-adapted brake
ca lipers, w hich ar e oper ated via a sw itch on the
in strument panel.
As you can see, t here's way too much new
technology in the CLA for us to be able to delve
very deeply into it in one magazine article, but we
w ill concentrate on the operation and d iagnosis of
spec ific systems in future issues of StarTuned. I

• Electronic Stability Program (ESP)

4MATIC is a great option. The rear axle carries
a multidisc clutch, and up to 50% of the engine's
torque can be directed to the rear axle.

This may look like terra incognita to you -- FWD,
MacPherson struts, and electrically-powered
steering -- but it's thoroughly modern and wor ks
superbly. Note the long link between the stabilizer
bar and the strut.
December 2013

25

Mercedes-Benz Mobil 1
Part Number

Quantity

BQ 1090144

Bulk - No Equipment

BQ 1090162

6/ 1 Quart Cases

BQ 1090151

Product Name

Product Description

Recommended Consumer Applications

Fully synthetic formulas designed
specifically for gasoline passenger cars

55 Gallon Drum

Low SPAsh. Available at most MB dealers

Fully Synthetic formula specifically
designed for Mercedes-Benz engines
that require the 229.5 Specification

.
.
Mercedes-B.e.nz ~ngm~s that require
229 · 5 Specification Oil

Fully synthetic formulation designed
to meet the requirements of many
European vehicles

Porsche A40. Many European vehicles.
HT/TS applications.

Advanced full synthetic formulas
designed specifically for diesel
passenger cars that have particulate
filters

Low SPAsh. Available at most MB dealers

Higher viscosity, advanced full synthetic
formula designed for performance
vehicles

Porsche A40. HT /HS applications.

Mercedes-Benz SPEC.

Mobil 1
Formula M 5W-40
Genuine
Mercedes-Benz Oil
MB 229.5
Specification
SAE 5W-30

A0009898301 USA6

12x1 Quart Cases

A0009898301 USAB

55 Gallon Drum

A0009898301 USA9

Bulk - No Equipment

BO 1 090010

Bulk - No Equipment

BO 1 09 0015

6/1 Quart Cases

BO 1090016

55 Gallon Drum

BO 1090135

Bulk - No Equipment

BO 1 090142

6/ 1 Quart Cases

BO 1090143

55 Gallon Drum

BQ 1 09 0133

16 Gallon Keg

BO 1090134

6/1 Quart Cases

Mobil ATF 134

BO 1 09 0166

55 Gallon Drum

Extra high performance automatic
transmission fluid formulated with
selected HVI base oils

Recommended for use in Mercedes-Benz
automatic gearboxes

Mobil 1 ESP
Formula MB 5W-30

BO 1 09 0165

12x 1 Liter Cases

Advanced full synthetic formulas
designed specifically for passenger car
diesels that have particulate filters

Low SPAsh. Available at most
MB dealers.

AdBlue"' 1/2 Gal.

A 000 583 0107

1/2 Gallon Bottle

Diesel Exhaust Fluid
55 Gal

BO 1470002

55 Gallon Drum

BO 1 09 0017

6/ 1 Quart Cases

BQ 1 09 0018

55 Gallon Drum

BO 1090019

6/1 Quart Cases

BO 1 09 0020

16 Gallon Keg

BO 1 09 0021

55 Gallon Drum

BQ 1 09 0083

6/1 Quart Cases

BO 1 09 0084

55 Gallon Drum

BO 1090169

6/ 1 Quart Cases

BO 1 090168

55 Gallon Drum

BQ 1090174

6/ 1 Quart Cases

BQ 1 090164

6/ 1 Quart Cases

BQ 1 09 0163

55 Gallon Drum

BO 1090023

BO 1090085

Mobil 1 OW-40

Mobil 1 ESP
Formula M 5W-40

Mobil 1 5W-50

Mobil 1 5W-30

Mobil 1 lOW-30

Mobil 1 15W-50

I

Mobil 1 Gear Oil
(Mobil 1 Gear Lube
75W-90)

I

Vehicles that require 5W-30. Corvette
approved.

Vehicles that require 5W-30 or lOW-30

Most vehicles that specify OW-20 (newer
Toyotas and Hondas), 5W-20 and certain
hybrids

Advanced full synthetic formulation
designed for enhanced fuel economy
and cold weather performance

Most vehicles that specify 5W-30 or
l OW-30

Multi-vehicle, fully synthetic fluid
designed to meet the demanding
requirements of modern passenger
vehicles

Vehicles that require Dexron Ill, Ford
Mercon and Mercon V performance
levels

55 Gallon Drum

Boosted, higher viscosity, advanced
full synthetic formula designed for
performance vehicles

HT/HS applications. Racing and Flat
tappet applications

12/1 Quart Cases

Exceeds the most severe service
requirements in both conventional and
limited slip applications

SUITABLE for use in modern high
performance automobiles like SUV's,
Vans and Light duty trucks requiring API
GL-5 level performance

Mobil 1 OW-20 AFE

Mobil 1 Synthetic ATF

Advanced full synthetic formula
designed for domestics and imports

Recommended for use in MercedesBenz, Volkswagen + BMW AdBlue"' (DEF)
applications

vanced u I synt et1c ormulat1on
designed to meet the requirements of
many newer vehicles including Hondas,
Eatds Cbt)lslets aad aewet Ia)latas
designed for enhanced fuel economy
and cold weather performance

Mobil 1 5W-20

Mobil 1 OW-30 AFE

Non-toxic solution that transforms
harmful Nitrogen Oxide (NOx) emissions
from diesel-powered vehicles into
harmless water vapor and nitrogen
designed to meet the requirements
of many domestic, including GM, and
im orted vehicles

Vehicles that require 5W-20

M
ercedes-Ben z automobi les are designed to perform on
the most challenging roads and conditions. Shouldn't the oil
used in Mercedes-Benz engines do the same? We think so.
Th at's why Mercedes-Benz and Mobil I have partnered ro
offer an unbeatable combination of total eng ine performance
and driving luxury.
Please have a look at our oil portfolio which is available
through your local Mercedes-Benz dealer. Our dealers are able
to offer you a w ide variety of oil grades at competiti ve prices.

Product Name

Part Number

Quantity

Product Description

Recommended Consumer A llcatlons

BQ 1090085

12/ 1 Quart Cases

Exceeds the most severe service
requirements in both conventional and
limited slip applications

SUITABLE for use in modern high
performance automobiles like SUV's,
Vans and Light duty trucks requiring API
GL-5 level performance

BQ 1 09 002464

Bulk - No Equipment

BQ 1 09 0171

12/1 Quart Cases

BQ 1 09 003064

55 Gallon Drum

Formulated from quality base stocks
combined with modern performance
additives to give the engine the expected
protection and performance under a
wide variety of operating conditions

Recommended for gasoline fueled
automobiles and light duty trucks
requiring an API SN/SM/SL/ SJ

BQ 1 09 003164

Bulk - No Equipment

BQ 1090172

12/ 1 Quart Cases

BQ 1 09 003764

55 Gallon Drum


requiring an API SN/SM/SL/SJ

BQ 1 09 003864

Bulk - No Equipment

BQ 1090173

12/ 1 Quart Cases

BQ 1 09 004464

55 Gallon Drum


automobiles and light duty trucks where
a higher viscosity API SN/SMSL/SJ oil is
preferred or recommended

BQ 1 09 012464

Bulk - No Equipment

BQ 1 09 0170

12/ 1 Quart Cases

BQ 1 09 013264

55 Gallon Drum


requiring an API SN/SM/SL/SJ


automobiles and light duty trucks where
a higher viscosity API SN/SMSL/SJ oil is
preferred or recommended

Extra high performance diesel engine
oils that help extend engine life in
the most severe on and off-highway
applications while delivering outstanding
performance in modern, high-output,
low-emission engines including those
with Exhaust Gas Recirculation (EGR)
and Aftertreatment Systems with Diesel
Particulate Filters (DPFs) and Diesel
Oxidation Catalysts (DOCs)

Specifically recommended for the
latest low-emissions, high performance
diesel applications equipped with
aftertreatment systems using Diesel
Particulate Filter (DPF) and Diesel
Oxidation Catalyst (DOC) technologies

Fully synthetic supreme performance
heavy duty diesel engine oil that helps
extend engine life while providing long
drain capability and fuel economy for
modern diesel engines operating in
severe applications

Recommended for use in all super high
performance diesel applications, including
modern low emission engine designs with
Exhaust Gas Recirculation (EGR)

Formulated to provide excellent high
temperature performance with superb
adhesion, structural stability and
resistance to water contamination

Recommended for industrial and marine
applications, chassis components and
farm equipment

Extra high performance, automotive
lubricant formulated from select base
oils and an advanced additive system
specifically for limited-slip differentials

Recommended for use in limited-slip
differentials, axles, and final drives
requiring API GL-5 level performance

Mercedes-Benz SPEC.

Mobil 1 Gear Oil
(Mobil 1 Gear Lube
75W-90)

Mobil Special 5W-30

Mobil Special lOW-30

Mobil Special l OW-40

Mobil Special 5W-20

Mobil Delvac 1 5W40

Bulk - No Equipment

BQ 1 09 0058

12/ 1 Quart Cases

BQ 1 09 0059

4/1 Gallon Cases
55 Gallon Drum

BQ 1 09 0086

Bulk - No Equipment

BQ 1 09 0051

Mobil Delvac 1300
Super 10W30

55 Gallon Drum

BQ 1 09 0060

Mobil Delvac 1300
Super 15W40

BQ 1 09 004664

BQ 1 09 0053

Mobil Special 20W-50

4/ 1 Gallon Cases

60 / 14 oz Cartridge

BQ 1 09 0079

120 lb Keg

BQ 1 09 0080

400 lb Drum

BQ 1 09 0098

40/14 oz Cartridge

BQ 1 09 0096
Mobil Lube HD
Plus 80W90

55 Gallon Drum

BQ 1 09 0078
Mobil Grease
XHP 222

BQ 1 09 0052

120 lb Keg

BQ 1 09 0097

400 lb Drum

r
FWD & MacPherson Struts
Change the Collision Repair Game

Many advanced
steering, stability
control, and propulsion
technologies in the front-drive
CLA depend upon precise suspension
geometry for proper vehicle operation.
Here are some front wheel drive suspension
basics for collision repairers who will be working
on this history-making model.

If y ou work exclusively on Mercedes-Benz vehicles, this will
be new to you. Of particular importance in collision repair
are the position of the cradle, and differences in suspension
alignment set tings. Note the long stabilizer bar links.

For the youn g, upsca le market th at the CLA
250 is i ntended to att ract, it offers lux ury, a ton
of advanced technology and sa fet y features, and
aggressive design cues, all at a new, compet it ionbusting price poi nt. Technicians - i f you cut your
coll ision repa ir teeth on Mercedes-Benz rear
wheel drive vehicles, read on because FW D and
MacPherson stru t front suspension mean there are
some new things to take i nto consideration.
The suspension of this front w heel dr ive model
is tasked wi th controll ing veh icula r movement
under a vari ety of speeds, weight loads, road
condit ions, and driver intentions. This routinely
requ i res resisting or red i rec t i ng t he k i net ic
energy of a 3,300 lb. vehicle t hat is in a consta nt ly
changi ng state of motion.

THAT NEWTON GUY
Newton's First Law says t hat a body in mot ion
will continue t hat motion u nti l it is acted upon by
an opposing force. Just to make l ife fun , Newton's
Second Law says t hat there is always an opposi ng
force, and it w ill generally eq ual t he other.
Think about a veh icle about to enter a turn.
The inertial force established by t he vehicle's
speed, weight, and ba lance wa nts to pu sh st raight
30

Mercedes-Benz

StarTuned

ahead . As the driver t u rns the steer i ng w heel,
the cornerin g forces of t he ti res act against t he
mom entum of the vehicle to change its di rection.
Newton's First, meet Newton's Second.

A

LITTLE PATCH WILL HOLD US
A ll of the forces t hat cont ribute to di rectional
control, corn eri ng abi l ity, vehicle stabi l ity, velocit y
or t hrust, and r ide comfort mu st accomplish thei r
goa ls t hrough the small patch of t i re t read t hat
is actua ll y i n contact with the road at any one
t i me. The job of t he suspension is to turn, t i lt, and
pos ition t he wheels so t hat little patch of tread
maxim izes its gri p on t he road i n spite of all of the
di fferen t forces at play.
SECONDARY DAMAGE
Collision energy can travel t h rough t he veh icle
to other areas that may be on ly indirectly
related to t he point of impact, w here it can cause
seconda r y, or h idden, damage.

Secondar y damage may be di fficu lt to catch wit h a
trad it ional visual inspect ion. If you miss a bent strut
or control arm , the ti re patch won't hold the road
properl y, and your fi nished repai r wi ll come back
from the al ignment bay need ing add it ional work.

The position of the strut
towers is particularly
important. Any deviation due
to collision damage will have
a big effect on caster (not
adjustable), camber, and
vehicle dynamics.

If you want to avoid an unpleasa nt 5 o'clock
surprise (most likely not included on t he original
estimate), you must search for secondary damage.
Check for loose or worn ball joi nts, lea kin g or bent
struts, and damage to upper strut mou nts and lower
control ar ms, tie rods, and other key components.

Measure the distance between reference points
("VB, " not to be confused with a type of engine
the CLA doesn 't have) at each front strut tower. If
there is a problem with a strut itself, MercedesBenz recommends replacing only th e damaged
side, not both struts.

Since you are probably used to workin g on rear
w heel dri ve wit h upper and lower cont rol arm s or
w ishbones, you should rea lize that it's i mportant
to spend a little ex tra time maki ng sure that stru t
tower placement and cradl e alig nment match
OE speci fi cat ions. In its Work shop Informat ion
System (WIS), Mercedes-Benz recom mends tak i ng
a series of measu rements to check for bent fro nt
suspension components and mounti ng poi nts. The
l ist of measure ments includes, but is not l imited
to, t he distance between t he front bea rings of t he
front ax le carrier, between t he rear outer mounts
of the fro nt ax le carrier, between t he front bea r i ng
of the front ax le and the rea r outer mount of
the front ax le carrier, a nd the distance bet ween
suspension st rut towers.

THREE ANGLES, PLUS . . .
The big three suspension ang les to check on an
FVVD vehicle are the sa me as fo r a RWD -- cas ter,
December 2013

31

camber, and toe -- but there are some subtle
differences. We'll go through the basics here to
make it easier to see them.
Caster refers to t he til t of the steeri ng ax is when
viewed from the side of the vehicle. The steering
axis is a line drawn through the upper and lower
steering pivot points. On t raditional MercedesBenz vehicles, these would be t he upper and lower
ball j oints in t he control arm s. With the strut
system i n t he CLA 250, on the other hand, t he
upper pivot is the center of the strut's top bearing
mount and the lower pivot is the lower ball joint.
Regard less, positive caster til ts the top
pivot towa rd the rea r of the vehicle. When an
i magi nary l ine through the steering ax is meets
t he ground at a point ahead of the center point of
the tire contact area, it cr eates a sel f-centeri ng
force that helps keep the wheels pointed straight.
Th is is responsible for pu 11 i ng a vehicle back to
the straight-ahead position w hen the driver lets go
of the steerin g wheel while coming out of a turn.
Since the top strut mounting position on the
CLA 250 is fixed, caster ca nnot be adjusted.
Large deviations in specified caster
may be due to a bent lower control arm,
damaged or misa ligned front ax le carrier,
or body damage that affects the position
of the upper strut mount. A fter mak in g
the appropriate collision repa irs, compare
caster measurements on the vehicle aga in st
speci fications in WIS to confirm that you
have corrected the problem.
CAMBER
Ca mber is the inward or outward ti lt of
the top of the wheel when viewed from
the front or rea r of the vehicle. Measured
in degrees, an i nward tilt is said to be
negati ve, and an outward til t positive.
Proper camber helps position the wheel so
th at it contacts the road with as even an
amount of force as possible across the width
of the tire as th e spring compresses and
rebounds. This minimi zes uneven tread
wear, and, more i mportantly, helps keep the
vehicle rolling st raight dow n the road.

32

Mercedes-Benz

StarTuned

A difference in camber angle that exceeds 1/2 a
degree side-to-side wi ll cause t he vehicle to pull to
the side with the higher camber. In other words,
a vehicle wi ll pull toward the side w ith the most
positive camber, all other th ings bei ng eq ual.
Possible causes of camber t hat does not match
specifications include a bent spind le, strut, or
control arm, or collision damage that has shi fted
an upper strut mount to one side (the first th ing to
measure is the distance between the strut towers).
For safet y reasons, NEVER try to st raighten any
suspension components, such as struts or control
arms. If bent, they must be replaced.
Front suspension camber is adjustable on the
CLA. Check in W IS for the exact settings to
achieve the desired front axle camber.
TOE IN OR OUT?
Toe is simply a comparison of the distance
between the leadi ng and trailing edges of the
front or rear pa ir of tires. If the lead ing edges are
closer together than the trai lin g edges, ali gnment
is sa id to be " toed-in," and vice versa.

To adjust camber on the CLA 250, loosen the nuts (1b)
that attach the strut to the steering knuckle. Use a wedge
between the strut tube and the wheel rim to force the rim
outward to achieve a more positive setting, and to hold
the setting in place. Once you've got camber where you
want it, tighten the upper nut first, then the lower nut,
and re-check the setting. Torque the nuts to 110 Nm, then
twist an additional 90 deg.

Here's where RWD and FWD differ. With RWD, as
the vehicle is being powered dow n the road, t read
drag tends to push the leading edges apart. This
force is obviously not present while you are making
the adjustment, so the specification will typically be
toed in slightly to compensate for dynam ics.
With FWD, the front wheels are pulling the
vehicle forward whenever engine power is applied
to t hem, wh ich wou ld tend to force the lead ing
edges of the tires together. So, you mi ght ex pect
that the specification would be toed out. That
doesn' t take into account coasti ng, however,
during wh ich mode the forces would be the same
as t hose of a RWD vehicle. A lways check WI S
for the specified settin g, wh ich represents a
proper compromise. Mercedes-Ben z engineered
in less than 1/4 of a degree of toe-in. Permissible
difference in toe between the right and left sides
of the front ax le is ±0° 1O'.
Toe settings have a major impact on tire wear.
Excessive toe-in or out causes tires to scrub
against the road surface even w hen dri vin g
straight. If toe is off by 1/ 8 in. (3mm), each tire on
that axle w ill scrub the road sideways 28 feet for
ever y mile traveled. Too much toe-in accelerates
outer tread wear, w hile excess toe- out causes rapid
wear of the inside tire edge.

The front axle toe specification for the CLA 250 is
0° 1 (±10'). With the steering wheel and steering
2'
gear locked in center position, hold the tie rod
(10) and loosen the jam nut (10f). Rotate the tie
rods to adjust the toe angle (see WIS for rear toe
specifications and adjustment instructions).

Normal wear to the tie rod ends and other
steering linkage parts, in add ition to col I ision
damage, ca n cause toe to become out of
compliance w ith the carefull y-consider ed OE
specification s. A ny other toe setting w ill produce
the scrubbin g that eventuall y causes a feath ered
or sawtoot h wear pattern on t he tire.
Check for feathered or sharp edges by rubbing
your hand lightl y across the tread. If it fee ls smooth
when you move your hand toward the center of the
vehicle but rough when you reverse hand movement
toward the outside, the cause is excessive toe-in.
Sha rp edges wi ll point in the opposite direction if
t he problem is excessive toe-out.

THRUST ANGLE
If the steering wheel is not centered while the
vehicle's wheels are moving straight, or the body
appears to be movi ng at an angle ("dog tracki ng"),
you have a thrust angle problem. The first steps in
correcting th is problem include ensuri ng that sideto-side speci fications are met, and replacin g damaged
tie rods, control arms or other rear suspension
components. You can adjust rear toe to the vehicle
centerline as part of a fou r-wheel alignment.

RIDE HEIGHT

& SAi

If ride height is unequal by as little as 1/8"
(3mm) side-to-side, it ca n negati vely affect both
toe and ca mber. Sagg ing, bent, or broken spri ngs

Toe is adjustable in the CLA 's double wishbone
independent rear suspension using the cam bolts
(60a). If cam bolt repositioning does not bring
rear toe into specification per WIS, replace the
tie rod (60).
December 2013

33

can ch ange the vehicle ride height and ther efore
alter the suspension angles.
You can no longer jud ge whether or not ride
height is in balance by how hi gh the fender edge
on each side comes up your leg. Mercedes-Benz
measures the vehicle level side-to-side difference
in degrees, and speci fie s that t here ca n be no
more than ±1.3° difference between the ri ght and
left sides at the CLA front ax le.
Keeping the ti re patch in the ri ght place wou Id
be relati vely easy if road s were perfect ly smooth
and had no turns. Since that is not the case in
the rea l world, we have Steering Ax is Inclination
(SA I). This is accompli shed by hav ing the spindle
attached to the ax le at an angle t hat moves the
swivel line downward from the top position, thus
enlisting gravity to help keep the wheels in the
straight-ahead position and to significantly reduce
t he steerin g im pact of road bumps.
This angle projects the sw ivel line close to the
centerline of the t ire at ground level. The di stance
between th e tire centerlin e and the sw ivel line
at ground level is ca lled the "Scrub Radius." The
smaller (narrower) the scrub rad ius, the less effort
is req uired to turn the wheels. A smaller scrub
radius also minimi zes tire wea r. A positive scrub
rad ius projects the sw ivel line down at an angle
that projects the t ire centerline outboa rd of t he
swivel ax is at ground level. SA i and sc rub rad ius
must be the same side-to-side on t he vehicle.
Before attempting to adjust camber to fine-tune these
angles, look for a bent spindle, a strut tower that is outof-position at the top, or a misaligned front cradle.
Many other factors ca n negatively affect
suspension angles and front wheel drive
performance. For example, after a colli sion,
Mercedes-Benz req uires check ing for damaged
ba ll joints at the fl ange connecti ng the lower
control arm to the steering knuck le, and where the
link rod connects to the stabili zer bar.
By payin g particu lar attention to suspension and
steerin g linkage angles during colli sion repai r,
you will ass ure that a CLA vehicle has the range
of motion needed to maintain traction, stability,
and ri de com fort. I
34

Mercedes-Benz

Sta rTuned

17

Check front axle rubber boot (1l m in photo) of
flange ball joint (17), and boot (1 Om) of ball joint
(10k) at link rod end (10) for leaks and condition.
Check link rod ball joints for play by pulling and
pushing on the stabilizer bar (11). Also check
ball joints by firmly pulling and pushing on lo wer
control arms (18). Photo is of a 2004-12 A-Class
(not sold in the U.S.), but instructions apply to the
CLA as well. If the rubber boots leak or the ball
joints show signs of excessive wear, MercedesBenz requires replacement of the applicable lower
control arm or link rod.

STRUT-RELATED NOISE COMPL.MJ

1. Use the following procedure to ab,e

noise before replacing a strut:
2. Determine the side causing ~
by driving with one side of
on a rough surface.
3. Unhook the stabilizer bar
to the test drive and chec
noise changes.
4. Release tension on the s
suspension strut and tiSJ
to-drive state.

noise source.

4

NET

Sourcing Mercedes-Benz
Repai r and Parts Information

Mercedes-Benz Wholesale Parts

Extens ive information on
Genuine Mercedes-Benz
Service Parts such as
Brakes, Wipers, Filters,
Batteries and Oil

Revamped WebParts
overview page and
refreshed manuals on
WebParts and the EPC

Genuine Mercedes-Benz
Remanufactured
Parts Catalog and Core
Return Policy, as well as
cu rrent price updates

StarTuned magazine
section with archive
search functionality and
downloadable articles

www.mbwholesaleparts.com

@ Mercedes-Benz

COMPLIMENTS OF R B - OF ATLANTA, INC.
M
770-390-0601

--- $65·~
.,_
__,...A203A210) 12

@-

Performance. Reliability. Success.
With our competitively priced rep lacement parts, you no longer have to settle for anything less than
Mercedes-Benz quality. But that's just part of the story. You see, our brake pads, rotors, v-belts and
spark plugs all carry a 1 2-month, no mileage-restriction warranty. So our parts are not only a great
deal. They're a great value. Since they're genui ne Mercedes-Benz, you can have confidence they'll
last, and so wil l your relationshi p with your customers.
Contact an authorized Mercedes-Benz dealer or learn more at www.mbwholesaleparts.com.

n

MSRP excludes state and local taxes and freight applicable. Prices rllil'J v.1<y by dealer. Se< )l'.Xlr autho<ized
Mercedes-Benz dealer fOf additional details or a copy ol the Mcrccdes-6cnz parts limited warranty.

@

Mercedes-Benz

Star tuned Magazine December 2013

Recomendados

Recomendados

Más contenido relacionado

La actualidad más candente

La actualidad más candente (6)

Similar a Star tuned Magazine December 2013

Similar a Star tuned Magazine December 2013 (20)

Más de RBMParts

Más de RBMParts (14)

Último

Último (10)

Star tuned Magazine December 2013