TO OUR READERS IN THIS ISSUEWe lcome to StarTuned, th emagazine for independent service 4 ANOTHER CHANCETO BURNtech nicians working on Mercedes- Just like a blacksmiths bellows, the Mercedes-Benz AISBe nz veh icles. You r Me rcedes- Benz "fans the flames," promoting rapid oxidat io n of pollutantsdea ler sponsors StarTuned and in the exhaust stream.provides the information comingyour way in each issue .Mercedes-Benz wants to prese nt theinform ation you need to know to 10 SAFE & SECURE -diagnose and repa ir Mercedes-Benz MERCEDES-BENZ PNEUMATICcars accurate ly, qu ickly and the f irst CENTRAL LOCKINGt ime ; text, graph ics, on-l ine and other One of the convenience features used most by yourtechn 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 byFeature articles, derive d from making it pneumatic instead of electrical.approve d company sources , focuson bein g useful and interesti ng.Our digest of technica l informationcan help you so lve unant icipated 16 A QUESTION OF TIMINGprob lems qu ickly and expertly. Mercedes- Benz timing chains and tensioners lastOur list of Me rce des-Benz dealers and last. But, given the tremendous numbe r ofcan help you f ind Genuine miles people put on these vehicles, they will needMerced es-Benz Parts. attention sooner or later.We wa nt StarTuned to be bothhe lpfu l and informative, so please letus know just what kinds of featuresand other diagnostic services youd 26 THE STRAIGHT & NARROWlike to see in it. Wel l continue to When evaluating chassis integrity after collis ion damagebring 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 definitelycovering the different systems on makes these extra steps worthwhile.these vehicles.Send your suggestions, questionsor comments to us at:StarTuned 31 GENUINE MERCEDES-BENZOne Mercedes Drive PARTS ... NEARBYMo ntvale, New Jersey 07645 Wherever you are in the United States, theres a nearbyPhone: 1 8002256 262 , ext. 7112 source of genuine factory parts for your customerse-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 ofMBUSA. 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 ousinjur 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 isinformat 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 assistth 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 repairscorrect 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 hasth at condition. StarTuned is a registered trademark of MBUSA.
STARTUNEDInformation for the Independent Mercedes- Benz Service ProfessionalFebruary 2009 U.s. $6.00 € 1 2.50 Volume 9 Number IGroup Publisher Contributing Editor MBUSA Technica l Production ManagerChristoph er M. Ayers, Jr. Chip Keen Content Advisor Devon Ayerscayers@cmacomm.com ckeen@cmacomm .com Donald Rotolo email@example.com Donald.Rotolo@mbusa.comSenior Project Director Contributing Editor Circulation ManagerTamra Ayers Ke rry Jonsson MBUSA Project Manager Joann Turnertayers@c macomm.com firstname.lastname@example.org Stephen Langelotti j turner@cmacomm .com Stephen .Langelotti@mbusa .comEditorial Director Contributing Editor List ConsultantBob Freudenberger T Nash om Art Director NFocusbfreud@cmacomm .com email@example.com Jef Sturm firstname.lastname@example.org
Just like a blacksmiths bellows, theMercedes-Benz AIS "fans the flames,"promoting rapid oxidation of pollutantsin the exhaust stream Whether you believe technological the fire in the old two-way catalyticdevelopments are motivated by tightening converter. In th e early 80s when thegovernment regulations, or by the desire to three-way cat became popular, the airadd va lue for new-car buyers, theres no was piped into the cat downstream of thedoubt that they are coming along at an redu ction section after the engine warmedever-increasing rate. Secondary air injection up so that it wouldnt interfere with thesystems, however, have a long history - reaction that broke down NOx, yet wastheyve been fighting air pollution since the available for the oxidation section.1970s. Of course, theyre way different todayfrom what they were then . Seltless Originally, a belt-drive n pump forced airin to the exhaust manifold to help oxidize A modern Mercedes-Ben z secondary AISescaping HC and CO. This was taken one (Air Injection System) does away with thatstep 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 systems 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 MEs 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 whats 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 youre 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 toIModel ! MEl IA c t iva t ions~ R AIR pump repair. Short of removing the cylinder head for am- 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 engines 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, theyve 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 inMercedes-Benz arc hives is from over 40 years ago. Back then, engin eintake manifold vacuum stored in tanks did the lock in g, but the systemsoon evo lved to use comb ination vac uum /press ure pumps to supp ly theforce needed. From 1983 onward, the change from vacuum topressure 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 theway, 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 theres 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 whats 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, its time to delve If you re not sure what youre dealing with, go to the into the EDW. passengers door and unlock. If all the other doors do the same, yo u ve got multi-point. If not, eith er youre PSE Modern System Operation working on a car with the old er single-point syste m (which unlocks on ly from the drivers door), or theres 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 youve 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 drivers 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 remoteCII_ _ 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
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 later1 Stal-Tuned 6
tion of Timing In order for a four-cycle engine to work, marginal, and making replacement at regularthere must be precise coordination among the intervals necessary. On the other hand, in aintake, compression, power and exhaust strokes . properly-maintained vehicle timing chains andAdvances in engine technology have helped related hardware can last well over 200,000increase performance throughout the rpm range. miles. Eventually, however, wear will reach theVariab le intake manifold runners optimize air point where diagnosis and replacement wi ll beinta ke velocity, variable valve timing has broad- needed, so you have to know how to performened the power band, and variable lift the job properly. This is usually not too difficultfurther fine-tunes air intake and exhaust flow a task providing you had the correct tools, andfor even greater performance, efficiency and any shop specializing in Mercedes-Benzeconomy. Regardless of how high-tech intake vehicles should have such items as a chainand exha ust events have become, maintaining pin remover/installer.basic cam/crank timing remains essential. First ScenarioKeeping Time _ _ _ Typically, you will need to deal with the timing Mercedes-Benz vehicles have always chain because of noise from a stretched chainexcelled in sound engineering and reliability. or weak tensioner, or because the cylinderFrom 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 removedsame engineering principles that are used to and put back into proper synchronization uponcreate a reliable ra ce engine are also used for reassembly. In the case of noise, the job is notproduction vehicles. One steadfast belief held by as daunting as you may think. Mercedes-Benzthe companys 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-Benzsix cylinder, V8 and twelve cylinder engines engines have the timing cover cast as one unitnatural ly have more mass to move than those of with the block, so the cover cannot be removedlittle 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 RemanufacturedAIC Compressor wasnt meant to be taken lightly. It is not only an exact replacementfor the original unit, its also remanufactured and tested to meet the same strictspecifications as the original, so it performs just as well. And like all remanufacturedparts, its covered by the Mercedes-Benz limited parts warranty.* In fact, the only detectabledifference you ll find between a Genuine Mercedes-Benz Remanufactured AlC Compressorand a new one is the price. Which were sure youll find quite refreshing.ITS ALL I N THE PROCESSRemanufacturing 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.
A QUESTION OFTIMING Continued from page 17 lnf~bOXl UIIIMI ~ 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 Iotlen the engine Is cranked. step-by-step procedures are 4 Tum £t1e crankshaft slOVi1y In the engines 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 clotl1 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, its 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,mers Mercedes can quickly lase the shine fram its exteriar.And because that is annayance enaugh, we keep th e casts far a reprir fS ,loy; ~: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-assistedWl._ 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 wont 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 . Dont , -- ---, 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 Thats why its important to replace both old one. Resetting the tensioner is critica l. As you alu minum seal ing washers even if youre reusing ran the new cha in in and the old one out, the the old tensioner. By the way, when ordering a tensioners 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
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
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FEATURE ARTICLE / COLLISION REPAIRThe Straight & NarrowWhen evaluating chassis integrity after collision damage you need totake the extra steps to verify straightness. The inherent value of aMercedes-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 wasstatistics co mpiled in the last fewye ars an d you will notice an One of the first steps that is caused by this collision. Althoughincrease in vehicles defined as a often overlooked and/or taken for we realize this is not always t hetot al loss by insurance companies . granted is the damage assess- case, it is often a good idea toThe reason for this is multi- ment. This is more than just a visu- start pulling the frame in a linearfa ceted . Increases in the cost of al overview of the parts that will direction extending the body frontpa rts, the short age of certified need to be replaced. A deeper to rear. Pulling fron t to rear wi llbody techs, and collision repair analysis should be incorporated "stretch" the chassis into afac 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 frametri buted to the overall price of a direction. You should think like a panels this will not always be therepa 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 theadded cost. Exotic metals, con- It sounds like common sense, but framework at 90 degree angles tostruction welding technology and this usually gives a good indication the panels original location . Thisfastening techniques have all of what points you should start may take several steps as yourequired retooling and training, pulling from . Also, this may be a change the location and / or thewh ich adds to the overhead of any good way to gauge from what direction of the pull point to staycol lision repair shop . Mercedes- direction you should start pulling perpendicular to the panel you areBen 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 framerepa 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 isimportance of returning the vehi- gives you the total surface area of developing a repair plan.cl es structu ral integrity to its pre- all of the damaged panels . Even ifcollision state. When dealing with the damage in this area is minimal, Measuring Up frame damage, its 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 ..... 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 • LUlIts"m O Al~mlolUm . PI.a"~1 IB Oala ShH I230 Bodyfuluru Mod. rn hybf1 dbO"Ystructur, Intludlng hlgh-,ltenglh sin. alumnum and mag onium • D. bClllbl, !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 metalswith dif ferent strength levels to achieve structural strength andoccupant safety. A visit to www.mbcollisioncenters .com andyour membership gets you this important data.Car Bench is a Mercedes-Benz approved alignment jig for framestraightening. There are various models available, and by visitingwww.carbenchna .com you can arrange bench rental and downloadmeasurement 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-BenzWith 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 hemation is only used for diagnostic purposes, particularly on Car Bench, and the Celette chassisolder models built before the turn of the millennium. You can alignment bench. If you have invested in the Celette or Caruse these measurement points to see how bad the damage is. Bench jig, you can access thosethe bench manufacturers specifi- measurements from their web-cations . Here is where a hard sites. The Celette website isdec ision has to be made: Is the www.celette-us.com. On the homef rame damaged beyond repair? page, select the "Fixture benchNo one wants to put in all the Setup Sheets" field, then selectlabor to get to this point and not your model chassis. There may berepair the vehicle. Tota ls should VIN number differences, so behave 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, selectchassis damage was measured "Support," then "Resources." Here is a Celette bench withoff of a K-point. That is, a point From there, select the "+" symbol a 230 chassis set up forwithin 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
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COLLISION REPAIR / SUB FRAME R&RBending ToYour Will Once the chassis is on the bench Dor; . no. tr«I~~~! ""11 1 01 s..o._~ .. ","",and the measurements have beentaken, 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 aresome relatively new concerns withMercedes-Benz designs and metalcomposition . In some cases, ofcourse, the damage to a panel willbe so great that straightening maynot 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 lniCknessto rep lacement. In the case ofhigh-strength steel, this becomesa requirement. High-boron steel is With your paid subscription to www.startekinfo.com. you canvery difficult to reform after crash access step-by-step instructions for alignment bench assemblydamage because it is so strong. and measurement procedures. You also are provided withMercedes-Benz uses fou r grades replacement procedures for interior structural panels as wellof steel: mild steel, high-strength as exterior body panels.steel , modern high-strength steeland final ly ultra high-strength virtually impossible to reform and strength steel and weld or bondsteel. Mild stee l is much easier to will need to be replaced. When and rivet in the new sections. Inpul l. The higher strength steels can damage is localized, it is much the case of the 215 chassis, yoube pul led, but often return to the easier to cut out the damaged sec- have to be even more carefu lpre-pulled shape . Ultra high- tion and replace it. pulling panels since high-strengthstrength steel is heat formed, so Ultra-high strength steel is more steel and mild steel is mated withwithout 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 thethe bench. Points on the and align lower-strength steels, Mercedes-Benz recommendedchassis 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 the230 chassis, you need to be in the process. Use ultra high- chassis you are working on shouldaware 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