j fSTARTUNED    Information for the Independent Mercedes-Benz Service Professional                                        ...
FIRE...              . . . on all eight with www.startekinfo.com.Mercedes-Benz USA Dealer Workshop Services is the source ...
i;,!(•..•-•::•:. •.•.••:4:-,.:::^.fv;                                                         XXX+   fXXX<                ...
Iff   -it,.:.PI-H-iilS                      One of the                                                                   I...
~ln any team sport, players need to work together             dedicated ignition module controls the ground sideto achieve...
IGNITIONwere dealing with DC, that means when the                       tracks. This means the "electromotive force" willp...
—best combination of fuel efficiency, power, and                   Since preignition can slow down the speed of thelow emi...
IGNITIONcontrol ignition timing per cylinder, accurately                 the problem. Also, ignition can be used as a tool...
line, burn time, and coil oscillations. With a low-         from the output tower to its ME-controlled ground.current prob...
e DeaEvaporative emissionshave been tested andmonitored by the MEsince the beginning ofOBD II regs in 1996.This system has...
—                                                             Believe it or not, evaporative emissions controls           ...
SEALING THE DEAL Overview-Just as in the past, gasoline vapors that form inthe fuel tank are directed to a charcoal canist...
—Vehicle                |211.070                                                               Control unit    ME-SFI 2.8 ...
The Advantages of GenujMercedes-Benz Rem;                                                                          Mercede...
•                GENUINE MERCEDES-BENZ                REMAN A/C COMPRESSORS                                      REMAN PAR...
-t:,,i  SEALING THE DEALsystem you will simply see smoke coming out of the                                         subject...
^^3METALLI?t    , usaiysa Km                                                                                %             ...
As Good18   Mercedes-Benz   StarTuned
Chemical ccnding through the use of structural             a collision. Automakers are now aware that the mix  adhesiyesis...
As GOOD As NEW—For example, some repairsmay only require a two-stage                                       STRUCTURAL BOND...
STRUCTURAL BONDING BENEFITS                 High       Rely on other joining               Replication mode               ...
As GOOD AS NEWthan the materials being bonded. Be cognizant                                          and assemblies that a...
tin                                                                                         accidents. Specific year/     ...
As GOOD As NEW      Use the approved     attachment methods, be                                               ADHESIVES MA...
StarTuned Magazine February 2012
StarTuned Magazine February 2012
StarTuned Magazine February 2012
StarTuned Magazine February 2012
StarTuned Magazine February 2012
StarTuned Magazine February 2012
StarTuned Magazine February 2012
StarTuned Magazine February 2012
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StarTuned Magazine February 2012

  1. 1. j fSTARTUNED Information for the Independent Mercedes-Benz Service Professional • February 2012 U.S. $6.00 €9.00 Volume 12 Number I ^m % One of the Star Points: Ignition Sealing the Deal• Good As New on Air lfc- ! Mercedes-Benz
  2. 2. FIRE... . . . on all eight with www.startekinfo.com.Mercedes-Benz USA Dealer Workshop Services is the source for all the technicalinformation needed to support, service, and maintain Mercedes-Benz vehicles.Mercedes-Benz workshops rely on DWS products and services for getting jobsdone quickly and more efficiently. Our products include: STAR Teklnfo with WIS-net (Workshop Maintenance Manuals and Sheets Information System) STAR Service Manual Library CDs Electrical Troubleshooting Manuals WIS and DAS software updates Installation Instructions Star Diagnosis System (SDS) Technical Bulletins Operators Manuals and COMAND Manuals Campaigns Mercedes-Benz Equipment Mercedes-Benz Special Tools Inventory of technical publicationsSTAR TeklnfoDealer Workshop ServicesEngineering Services, Mercedes-BenzMercedes-Benz USA, LLC.
  3. 3. i;,!(•..•-•::•:. •.•.••:4:-,.:::^.fv; XXX+ fXXX< IN THIS ISSUE WelcometoStapTunedUhe-magazine for independent .service tecl*n;piapsvvorkingor-MerGede3-3enrvenie)es. Y31V ^ ; iMsroedes&enzdealejFsponsoPslSbnlTun^ • : ; ; : . r : " v ^ r "l":::.:::-:l-V;:.i ::J ^ - l ! r J x information coming your way in.each issue. - * t f J , + " * f q - ^ L J * ^ J, * 14. * ^ 4 ONE OfcliHE STAR POINTS: IGNITION Mercedes-Benz wants to present the information you-need to , 111 Our-digest of .|help;yojjsdlve • -v 5 " unanticioated prcplems quickly and expert*. : • ;fiieaseletiiS^nowiist-whaiskindsw features md;other diagnostic: seiwides^dufdl like.foiseeijniifcfotefteontlnueitb-; , •<:• bring you, selectediservice ibuUe^jhsfromiiylercedleVBenz and .articles covering the different^ystems-Ontnese vehicles. P - J /oufsuggescioTis,^---"" ^ - - • — - - - - • - L - 1 :StarTuned iQne Mercedes Drive., ; ••• •• . ! • Montvae, Ney.vJersev-076.45 - "... : Phone: 1 300 225 6262, ext. 7112 " •• Xh ;e-mail:andrew.v.ebb@mbusa.coin •~X:X StarTunpj ts a p u b l i c o - c, M m eete Be* 2 USA, I L : W J s n JNa pari q f f ^ i . magaziriu ;i,ay bt reproduced without tht e<pre<5s written* permsBJon .of MBWSA* Editorial and Circulation Offices l " J - r Rn - - " . - k . ~ ;: _ liar Vehicle servicing perfci-ntu ^y untrained ipersrjns could reskill in jriou linjiir. to those persons or other . ifcrnihiici 1 c: - - n ink m a ^ m <* hy trained jrtform these information trained technicians have the equipment, tools, safety instructions, ?nd ITCV> hrw 1 perform repairs correctly and safety. If a condition Is descnbed.DO NOT v rr.at a ^xx-x xr,Ay.xXXrxx^xxx^l topic covered in these cases automatical^ applies t« vnur vnrildle or i^1 your vehicle has that condition. Stan : , • 11 regisfe Itrademart MBUSA . ~r-* ^ yxx x^yxxx-x^ x-x:.. xxm. xx .-. ••• i-".,::;V".., •• ; ;--;i - -v:-. •• , , , ;"V:-, Group Publisher Contributing Editor 18 AS GOOD AS NEW X: Christopher M. Ayers, Jr. Tom Nash cayers@automotlvedatarriedia.com tnash@3UtQmotivedatamedfa.odm Chemical bonding".^ .increasingly. H Editorial Director MBUSA Technical Content Advisor preferred.joining technology. Bob Freudenberger Donald Rotolo •"•*:-•:• bfreud@automotivedatamedia.com : Don8id,RQtolo@mbusaxom Contributing Editor MBUSA Project Manager Bob Ghabot Adam Green bchabot@automotivedatamedia.com adam.greeh@mbusa.com 26 FLOATING ON AIR Contributing Editor Art Director & Circulation Mgr. Kerry Jonsson Christopher M. Ayers III Although Mercedes-Benz otTers a kjonnson@automotivedatamedia.com ayersc3@automotivedatamedia.com hydraulic suspension, system (Active. Body Control, or ABC), theres an Visit us at our website alternative. AIRmatic suspension www.MBWholesaleParts.com t o yievv this issue doesnt need hydraulic fluid, or a belt- and all past issues of StarTuned, along with a wealth of driven high-pressure pump to maintain information on Genuine Mercedes-Benz Parts. a level stance,Vehicles so equipped float on a cushion of air, so how do we: To locate a Mercedes-Benz dealer near you, keep them afloat? go to www.mbusa.com.
  4. 4. Iff -it,.:.PI-H-iilS One of the I," >: *-: •. •- :- • it! •••• ilrt ..:•.••, ••-;:• •;L.. •••::••• LWM £ * •-, ?• :; •,: . •: •t...j«f3 i : • ~ , " %wtipropertyymfy i S$$^- gm<0tm*i>yrmnge mqyims three elements to w$rkix^getherin perfect harmony: compression, :J {S,*:; fuel, and, our subject here, spark. Maintaining this harmony insures the legendary power and performance of Mercedes-Benz vehicles.
  5. 5. ~ln any team sport, players need to work together dedicated ignition module controls the ground sideto achieve a goal. The same applies to the of the coil. When the coil is grounded, a magneticinternal combustion engine. The basic engine is field is created in and around the primary windings.engineered to take in and compress quantities of The secondary windings contain many more wrapsair. The fuel system combines a flammable liquid of fine wire than the primary does. When thehydrocarbon with this air at the optimal ratio to module or computer "un-grounds" the coil, theprovide a clean-burning mixture. In a diesel engine, circuit is broken and the magnetic field collapsesignition occurs naturally, so when that happens is into the secondary windings, and the result isdetermined by the timing of the injection event. In high voltage. The ignition systems found on oldera gasoline engine, on the other hand, the mixture vehicles before the mid-90s had coils with singleis compressed to a point where it is ready to secondary towers. The spark out of this tower wouldburn, then the ignition system provides the high- be sent to a distributor cap and rotor, which wouldvoltage, low-amperage spark that ignites it. If then distribute the spark to each cylinder in its turnthis spark were to occur at the wrong time in the timed to coincide with its piston approaching TDCengines cycle, harmful emissions would increase, (Top Dead Center).fuel mileage would fall, and performance wouldbe reduced. Internal engine damage is anotherpossibility. In the old days, we were able to adjust How We Get kV from Just Vspark timing by twisting the distributor, or changing -The induction phenomenon that generates manythe gap of the ignition points. Now, of course, the tens of thousands of volts at the spark plug gapcomputer provides vastly more precise adjustments from mere battery voltage is both interesting andthroughout the rpm range. subtle, but its not our purpose here to provide a detailed physics lesson. Suffice it to say that the ignition coil is actually a voltage step-upThe Ignition System transformer. Like all transformers, it only transforms~To properly diagnose ignition systems, you need voltage from its primary windings to its secondaryto have an understanding of how they work and windings when the current flow changes. Sincehow they can affectdrivability. The system x ;:::; K <I !D -"-I d ««•««*< ^ ^ DUqnctticis divided into twoparts, primary andsecondary. The primaryside controls whenspark occurs, and issometimes referredto as the triggeringmechanism. Thesecondary side doesthe actual work ofigniting the mixture.It all starts in theignition coil, which isfed voltage throughthe vehicles powerdistribution system. An Using startekmfo.com you can pull up a wiling diagram of the ignition system, such as thisME (Motor Electronics) one for the CLK 320.You can see that the center pin (#2) is the voltage supply to the coil.control unit, or a You can check the resistance of the coil windings between this pin and the outer two. February 2012 5
  6. 6. IGNITIONwere dealing with DC, that means when the tracks. This means the "electromotive force" willprimary circuit is broken by releasing the ground. not make it to the spark plug to ignite the mixture.The primary has only a few windings (and thus a The cylinder will not produce power and raw fuel wilrelatively low resistance), while the secondary has pass into the exhaust stream.many more windings (and a higher resistance). —This total lack of, or incomplete, combustion is—While the coil primary circuit is grounded (called called a "misfire." On 96 and later models, OBD II"dwell"), the current flowing sets up a powerful regulations require that misfires be monitored, and,magnetic field inside and around the coil. When if one occurs, that the MIL (Malfunction Indicatorthe ground is released - changing the current flow Lamp, also called the CEL for "Check Engine Light")- t h e energy in the magnetic field is released in the must flash on and off. This warning is emphasizedform of a higher voltage through the coil secondary. because of the fear that unburned gasoline willWhen this voltage reaches a certain level, an overheat the catalytic converter.electrically-conductive spark forms across the sparkplug electrodes. Because the spark is conductive, —Of course, for many years Mercedes-Benz hasthe voltage drops somewhat and remains relatively been using "COP" (Coil Over Plug) ignition, whereinconstant until the energy stored in the coils theres a small separate coil for each spark plug.magnetic field is exhausted. This eliminates the distributor cap, rotor, and plug wires, so there is never a problem with those—Traditionally, this has been described as components. The coils themselves or their control"collapsing lines of flux" (meaning the primarys circuitry can still fail, however.electro-magnetic field) inducing high voltage in thesecondary windings. The Basics Of Ignition Timing-The secondary voltage must be kept high as —It is important to know that spark does notit passes through the coil wire, distributor cap, occur at TDC. This would be too late. The pistondistributor rotor, back through individual spark plug would already be on the way down by the time thewires and finally across the spark plug gap. This expanding gases started pushing on it. So, the air/high voltage, like any electrical current, is looking fuel mixture is ignited just before the piston reachesfor the easiest path to ground. So, it will "leak out" the top of the compression stroke, and how muchof any component that has cracks, cuts, or carbon before is calculated electronically to achieve theOn 10-1 and I I I engines, the waste spark ignition system is used. A single coil serves the plugs of two cylinders, oneunder compression the other during the exhaust stroke.You can see here that the resistance of the secondary windingis 7,370 ohms.The primary resistance is about .25 ohm.These readings will change slightly with temperature.6 Mercedes-Benz StarTuned
  7. 7. —best combination of fuel efficiency, power, and Since preignition can slow down the speed of thelow emissions. In the past, this "advance curve" crankshaft, it can have the same effect as misfiringwas determined on the basis of rpm by means of in turning on the OBD II MIL, and may also causecentrifugal weights, and engine vacuum by means of failure of a state or local emissions test. Also, unduea diaphragm and lever mechanism. stress is put on the pistons, rings, connecting rods, and bearings. Multiply this by millions of revolutions and you can understand how catastrophic engineProblems w i t h Ignition failure happens. So, the timing of the spark and the— As we said, if the spark occurs too late the piston actual spark output need to be verified during thewill already be on the way down and power output testing of any drivability problem.will be reduced. If the mixture ignites too early, onthe other hand, the flame front will hammer therising piston. This will also reduce power output Who is in Control of Timing?because whats wanted is a smooth push, not an "When it comes to ignition timing, you needexplosion, but it can also cause serious engine to understand that it is all computer-controlled;damage. This condition is known as pre-ignition, therefore it is difficult to test manually, and thatdetonation, or "pinging" from the distinctive sound is probably not necessary anyway. Basic ignitionit makes, and it can have multiple causes. Cheap, timing is set by a calculation of the ME control unitlow-octane fuel may ignite at lower combustion based on the crankshaft and camshaft positionchamber temperatures before the spark occurs. sensor signals. On earlier model engines, you mayHigher-octane fuels are more resistant to pre- only have one crank and one cam position sensorignition from heat and therefore will not ignite until even through you have a V8 with two banks. V12the spark arrives. Also, inexpensive fuels may not engines usually have two six-cylinder systems matedburn completely leaving carbon deposits behind together as System 1 and System 2. Later-model,inside the combustion chamber. These may retain more sophisticated engines have a position sensorthe heat of combustion and "glow," which can ignite for each camshaft, particularly if they also havethe incoming charge before the carefully-timed variable valve timing. The combination of crankshaftspark occurs. and multiple cam sensors allows the ME unit toOn a 119 engine, you should see a coil primary resistance of about .5 ohm between the two outer pins of the three-pinconnector. The middle pin is wired to ground and is attached to the secondary windings. Verify the ground connection for thesecondary windings. February 2012 7
  8. 8. IGNITIONcontrol ignition timing per cylinder, accurately the problem. Also, ignition can be used as a tooldetect misfiring cylinders, and also to test the to identify problems present in other systems. Youoperation of the variable valve timing system. As might perform static testing first, which is typicallya result, any problem with cam and crank timing a matter of checking the electrical characteristicswill be identified by the self-diagnostics. Other of the components. Measuring the resistance oftests, such as that for engine compression, can be a spark plug wire is a static test. Dynamic testingperformed, of course. usually involves measuring the kV and amp draw of the components as you would with an ignition— The next largest influence on the timing oscilloscope. Starting with static testing, you shouldcalculation is that of the load sensor. Since the always verify that you have battery voltage at theearly 90s, Mercedes-Benz has used a Mass Airflow coils positive terminal. A quick look at a wiringSensor (MAF) almost exclusively to measure engine diagram on www.startekinfo.com will help youload (it is a requirement of OBD II). If the MAF identify the coils voltage source. Next, you can testchanges ignition timing enough to affect drivability, the coils primary winding resistance. You couldyou can identify the cause of the symptoms with have readings from a few other coils to compare,additional testing. The additive and multiplicative but ideally you would use WIS (accessible throughfuel trim readings would also indicate there may be startekinfo.com) to get specifications.a problem with the MAF. ""Typically, Mercedes-Benz powers the coils by means of drivers in the ME control unit. You canTesting The Primary scope the primary trigger of the coil. The way the—What you will need to do to accurately diagnose voltage that results in the spark passes through thea MIL-on or drivability issue is to test and verify, secondary windings affects the electrical signal ofor eliminate, the ignition system as the source of the primary, so you will see the conventional firingThis coil is really two coils mounted in one housing.Therefore, there are two secondary windings. Short spark plug wiresare used with this dual-plug system, but they still need to be checked.You dont want to see much more than 2k ohms,or replacement is necessary.8 Mercedes-Benz StarTuned
  9. 9. line, burn time, and coil oscillations. With a low- from the output tower to its ME-controlled ground.current probe, you can monitor each coils amp Finally, there are engines like the 1997 119 that havedraw. The ME control unit will increase dwell with one coil wire per cylinder. The secondary windingrpm, but draw is typically limited to one amp. The runs from the spark plug through the coil to ground,critical part of the signal to watch is the rate at which is the center pin (brown wire) so you canwhich the amperage slopes upward. You can use check resistance across those two points.other cylinders that are not misfiring as a guideline. Using the Ignition SystemTesting The Secondary for Troubleshooting—The coil primary windings are only half of the —Monitoring the coils secondary output kV is veryequation. The resistance should be checked on important when evaluating the ignition system.the secondary side also. To do this, you will have You can tell exactly what is going on in thatto know how the coil is constructed. In the past cylinder under multiple conditions. You will needtwenty years, Mercedes-Benz has mainly used three an oscilloscope with an adapter for the various coildesigns for its ignition systems. On the older in- designs Mercedes-Benz uses. The first part of theline four 111 engine and six-cylinder 104 engines, a pattern you will come across is the dwell, or groundcoil-over-one-plug design is used with an additional time. This is when the primary circuit is complete.coil wire going to another cylinder, which is referred The next change you will see is often referred to asto as a "waste spark" system. This coils secondary the firing line. This is the initial arc across the sparkwindings fire at both ends, one positive and one plug gap. A high firing line generally means the sparknegative. There is no longer a direct connection plug electrodes have eroded leaving a gap that is toowith the positive side of the coil. Spark travels from wide, but a bad plug wire, or a lean condition canthe ground side of one spark plug electrode to the also be the cause. A relatively low firing line meanscenter electrode, then passes through the coil and the plug gap is too small, probably from physicalonto the companion spark plug. In the case of the damage, or perhaps a rich condition is present. 112 and 113 engines, a single coil fires two plugs. On After the firing line comes what is sometimes calleda 113, this happens in a single cylinder as each one "burn time." This is the condition of the spark whilehas two plugs. The design is essentially two coils in the mixture is being ignited. You would like to seeone housing, sharing the same power supply. The a smooth, flat, even line that would indicate idealplugs can be fired individually and are staggered to combustion. The final part of the pattern is the coilshelp completely burn the mixture in the cylinder. oscillations. These tell you if the coil is up to its task.You can check secondary resistance by measuring You should see minimal oscillations with a normal coil as the excess energy in the primary winding of the coil dissipates. No oscillations can mean aWhat you are looking at fi 2aa^OIV UIPROBE 0 1QVDC teUPfiOBE tOVOC shorted coil or loose connections. Trlfliftfis the primary waveformof a 119 engine.The -Taking the few steps outlined here should helppattern starts off with —&, you confirm whether or not the ignition systemvoltage to the coil, whichis then pulled to ground U is working properly, and isolate problems. Also,during the dwell period.When the ground is U looking into the secondary ignition system is an excellent way to diagnose other troubles with either the fuel system or the basic engine mechanicals.released, the spark line fl_Si_followed by a normal A t flVSBWE B»» OFF An accurate, informed diagnosis is why yourbum time (usually customers choose to come to you, and whatsbetween .8 and 1.8ms) are shown.There are minimal coil better than that? |oscillations from a single coil for a single cylinder. February 2012 9
  10. 10. e DeaEvaporative emissionshave been tested andmonitored by the MEsince the beginning ofOBD II regs in 1996.This system has beenone of the more difficultair pollution-reductionsystems to diagnose andverify. SDS software hasmade the job easier.
  11. 11. — Believe it or not, evaporative emissions controls have been around for over four decades. For most of that time, they were relatively simple, comprising a liquid/vapor separator in the tank, a charcoal canister with a vacuum-operated purge valve, a special gas cap that didnt vent pressure unless it exceeded maybe two psi, or vacuum until it reached several inches, and related plumbing (many of you wont remember that there was even a hose from the carburetor bowl vent). When the engine was started and run above idle speed, ported vacuum opened the purge valve, the stored vapors were drawn through a hose into the intake stream, and fresh air entered the canister through a filter. These systems not only reduced a vehicles hydrocarbon emissions by up to 20%, they also saved a little gasoline. And they were pretty much trouble-free. ^With the advent of OBD II regulations, EVAP had to go high-tech with the PCM actually performing tests to make sure the tank and hoses were vapor-tight. If not, commonly because the gas cap has been left loose after a fillup, therell be a MIL-on situation and youll get a visit from the customer. If a loose cap were the only potential problem, thered be no need for this article. But sometimes youll be presented with a diagnostic mystery.Vehicle Control unit ME-SFI 2.8| ActuationsY32 (Air pump switchover valve). M33 (electric air pump) ( fig), EURO 3 , EURO 4 . D4 )Y62jFueT injectors)M16/6 (Throttle valve actuator)M3 (Fuel pump)Y58/1 (Purge control valve)Y58/4 (Activated charcoal canister shut-off valve) i @ )Y31MJEGR vacuum transducer)Mixture adaptationElectric suction fan for engine or air conditioningFuel tank leak test ( @ )Ignition circuit shutoff T1/x (ignition coil(sj)Y22/6 (variable intake manifold switchover valve) ESC F1 This is a good example of why investing in an SDS will make you a true Mercedes-Benz specialty shop. Under the heading "Actuations," youll find various tests you can perform on the EVAP system, including activating the purge solenoid, shut-off solenoid, and EVAP leak test. February 2012 11
  12. 12. SEALING THE DEAL Overview-Just as in the past, gasoline vapors that form inthe fuel tank are directed to a charcoal canister for storage, then routed to the combustion chambers to be burned. Whats different today is the control of canister purging. In old systems, this was accomplished by the simple expedient of portedvacuum either drawing off the stored fuel vapor directly, or opening a valve that allowed manifoldvacuum to do the job. Now, of course, mixture management is much more crucial, and only the ME (or PCM) can provide the precision needed.—So, the purge solenoid, sometimes referred to asthe regeneration valve, is under the command ofthe ME. It is pulsed as necessary to allow manifold Here we are adding smoke and we have dosed the cut-offvacuum to reach the charcoal. solenoid. If you look closely, you can see a small amount of smoke coming from the vent. Is this enough to cause our—Under OBD II, if theres a leak in the EVAP system leak code? We wanted to he sure.the ME control unit needs to be able to detect it. Ifits less than the air that would be lost from .020-in.hole, its acceptable. If the leak is larger than that, —Mercedes-Benz uses the vacuum decay methodbut lower than that of a .040-in. hole the ME sets a to determine if there are EVAP system leaks. Thesmall-leak code. Anything larger than that results in regeneration valve, or purge solenoid, is pulseda large-leak code. If any individual part of the EVAP open to draw the system into a vacuum. The fuelsystem fails, the ME detects it. tank pressure sensor (FTP) measures the drop in pressure just as a MAP sensor measures the pressure drop in an intake manifold. When the FTPMeasuring EVAP Leaks signal reaches a predetermined level, the purge—Two strategies may be used to allow OBD II to solenoid is closed. With the canister close valvetest EVAP to see if everything is sealed properly. energized and the purge solenoid de-energized,One uses pressure decay, and the other vacuum the EVAP system is completely sealed. The vacuumdecay. In the former, pressure is applied to the should hold and the FTP signal voltage shouldEVAP system and measured. If the pressure drops remain steady. If the voltage changes, vacuum istoo quickly, a leak must be present. In the latter, being lost, so there must be a leak.vacuum is generated in the system and any drop isalso measured. Okay, How are We Going t o Test it?—In either case, measurement cant be —You could manually close the canister close valveaccomplished unless the normal channels are and open the purge solenoid. You could then watchsealed. This is the job of the canister close valve. the signal voltage of the FTP and allow the purgeRemember, fresh air needs to be taken into the solenoid to close while seeing if the FTP signalcanister to allow the vapors out. This air comes voltage changes. You need to know what a good FTPthrough the close valve, which is normally open. signal is without any pressure or vacuum in the fuelDuring the testing, the computer energizes the tank to verify that the FTP is reliable. You also havevalve, closing it. to know the change in vacuum by how it affected the FTP signal.12 Mercedes-Benz StarTuned
  13. 13. —Vehicle |211.070 Control unit ME-SFI 2.8 Another way you can check[Fuel tank leak test for leaks is to "smoke it." An During the fuel tank leak test the shutotT valve ot the activated charcoal canister Is closed and a vacuum Is built up in the fuel rank by operating the purge valve. The subsequent actual pressure loss may be max. 5.0 hPa within 60 s. EVAP-compiiant smoke machine Fuel tank pressure difference at start of test Fuel tank pressure difteience at end of test generates a small amount of Outgassing collection value pressure and blows smoke into Actual pressure loss the EVAP system. You still need to close the canister close valve to seal the system, but you dont need to run the engine. so as » » —Obviously, wherever you see smoke is where your leak is. You will have to expose theUsing the Fuel Tank Leak Test, you can vsatch the pressure in the fuel tank in plumbing to isolate the source,hectopascals (hPa). Here, the pressure increased by eight hPa over 60 seconds which can be time-consumingThe outgassing factor was because the gas cap was removed and reinstalled depending on the model yourebefore the test. working on. Also, if the purge solenoid is the source of the leak you will not see the smoke since it will enter the intake manifold first before exiting the air filter housing. Once you find the source and repair it, you will then have to drive the vehicle to verify your repair. The EVAP monitor is one of the more difficult monitors to run. Variations in outside temperature, fuel temperature, fuel level, atmospheric pressure, etc. all have an effect on whether or not the monitor actually runs, so this can take a lot of time. Using conventional methods will make it difficult to verify your repair. Is there a way around this dilemma? SDS to The Rescue —SDS offers advanced testing of this system. Not only will it allow you to verify your repair, but it can also be used in the diagnostic process to help determine the source of the problem. When accessing the ME control unit, you will probably look for DTCs first. Once you determine they are EVAP leak codes, you can start testing. Under the heading "Actuations," you will be shown a list of various components on the car that you can activate through SDS software. This also lets you know the computer is capable of groundingTo verify that the cut-off solenoid was closing, the vent port solenoids and is not the ultimate source of thewas blocked. There should be no difference whether the cut- problem. One of the actuations you can do is that ofoff solenoid is dosed and the vent port is blocked since they the canister close solenoid. This can be useful if youboth seal the system. However, there is a difference in theresults of the leak test. are smoke testing. If you apply smoke to an open February 2012 13
  14. 14. The Advantages of GenujMercedes-Benz Rem; Mercedes-Benz The best or nothing. uality, Reliability and ValueReman A/C Compressors are not rebuilt or refurbished, they are brought back tothe exact Mercedes-Benz approved specifications and tolerances, thus ensuringoptimal performance.Additionally, these units come preassembled with the clutch attached, so atechnician can get right to installing the entire assembly, saving time and money.By using Genuine Mercedes-Benz Remanufactured Compressors, you could save40% or more when compared to the cost of new. And like all of our remanufacturedparts, its covered by the Mercedes-Benz limited parts warranty.Genuine Remanufactured installed. Mercedes-Be,,;,Problem solved!hor more information, visit www.mbwhoIesaleparts.com.
  15. 15. • GENUINE MERCEDES-BENZ REMAN A/C COMPRESSORS REMAN PART MODEL REMAN PART VEHICLE MODEL VEHICLE MODEL NUMBER YEAR NUMBER1984-1992 190D2.2 A00023012I180 CL600, CL65 AMG, 2000-2006 A001230011180 S65 AMG. S600 260E, I90D2.5, :3()0TD,1984-2002 A000230241180 2000-2009 E320, S350 A000230911180 300D, 300CE, SL500 42 OS lit., 56QSEC/SEL, 2002-2007 C32 AMG A0002307811801986-1991 A00023025I180 560SL A000230971180 2002-2007 C230CL1.81986-1995 190/300 series, 1:3001) A000230II1180 CLK-Glass, C55 AMG, 2002-2010 A001230191180 300E, 300GE; 600SI., SLK55 AMG1986-2002 A000230051180 S 1.600 2003-2009 CLK500 A0012301611801990-2002 500SL, SI.500 A000230061180 2003-2010 SLS5 AMG A0012300211801992-1993 500SEI. A119230111 (80 E55 AMG, E320, E500, 2003-2010 A001230121180 400SE, 400SEL, 500SEC CLS5001992-1995 A 119230001180 S420, S500 ErClass, CLS55 AMG, 2 003-2010 A001230I4I180 CLS550 GOOSEL, S320, S600, A0002301711801992-1999 A001230551180 300SEL 2003-201O SL550 300SEi rtOOSEC. S600, A0OO230221180 SLK280, SLK300, A0012305411801992-1999 2005-2010 S320, CL600 SLK350 CI.500, 300/400/500 R350, R500, ML350,1992-2004 series, S/SLK/C/CLK/ AO0O2 307O1IHU 2006-2010 ML500, ML550, GL450, A001230871180 li-Class GL5501994-2000 C220, C2H0, C36 AMG A000230131180 R350, R500, ML350, 2006-2010 ML500, ML550, GL450, A002230521180 ML.320, M U 3 0 , Gl.550199H-20O5 A000230681I80 ML55 AMG 2009-2010 G300, C350 AOO12305011801998-2010 Ml.500, ML350 A00123028I180 2010 GLK350 A002230311180 ML350, ML500, E500, A0002309011801998-2010 201.0 E350, E550 A002230381180 S1.500. C/CL/S/G-Class Made with the same OE components as original factory parts Assembled to original Mercedes-Benz specifications Results: Mercedes-Benz Quality, Reliability and Value Remanttfactured for MercedesrBenz by Available only through your local Mercedes-Benz Dealer
  16. 16. -t:,,i SEALING THE DEALsystem you will simply see smoke coming out of the subject, this test has failed. To isolate the leak, youcanister vent. You can now close the vent solenoid can remove and block off various hoses, and re-runand see if smoke comes out anywhere else. the test. If it now passes, you now know the leak must be in the part of the system you blocked off.—If it still comes out of the close solenoid, then yousimply have a bad cut-off solenoid. You may want —Keep in mind that much of the EVAP system hasto verify that the solenoid is being grounded by the hard plastic lines, which you shouldnt crimp as theyME. It may be difficult to see if smoke is still coming will probably break, creating more leaks. The saferout of the cut-off solenoid. way is to remove the line at a flexible hose and plug it. In our test vehicle (211 chassis), we temporarily—The SDS software can also perform the entire blocked off the vent of the canister close solenoidEVAP test on newer chassis like the 211. This is a and ran the test again. During the test, the closesignificant time-saver. When you are done with your solenoid should be closed anyway, so blockingrepairs, you can test the system to verify that it off the vent port should not have had an effect onwill pass the monitor. The engine must be running our test - but it did. The EVAP system passed thefor the test since you need engine vacuum to draw test with the vent port plugged. This told us thatdown the EVAP system. The automated test grounds the close solenoid wasnt completely sealed andthe close solenoid and opens the purge solenoid. allowed the vacuum to drop in the system. On the 211, the canister close valve is incorporated into the charcoal canister assembly, therefore the entire Monitoring the Situation canister had to be replaced.—Youll see the FTP signal displayed in hPa insteadof a signal voltage on a graph. Youll also see thedrop in pressure (relative vacuum) as the purge Verificationsolenoid is opened and the cut-off solenoid is —Once the new replacement canister is installed,closed. Watch the FTP reading over time as the you should run the EVAP system test again. Youpurge solenoid is allowed to close. Observe the should see the FTP reading stay stable after thegraph as the 60-second test is run. The parameters regeneration solenoid is closed. If the systemare also given in the test screen. In the case of the passes now, you can return the vehicle to the211 chassis, the SDS does not want the FTP reading customer without the worry of he or she returningto increase by five hPa over 60 seconds. On our test multiple times for the same problem. | After installing the Vehicle 1211.070 Control unit |ME-SR2.8 new canister cut-off |Fuel tank leak test solenoid assembly, During the fuel tank leek test the sftutoff valve or the activated charcoal canister Is closed and a vacuum Is built up In the fuel tank by *j the leak test was operating the purge valve. The subsequent actual pressure loss may be max. 5.0 hPa within 60s. Fuel tank pressure difference at start Of test -19.8 hPa run one more Fuel tank pressure difference at end of tost -18.2 hPa time. The pressure Outgassing correction value 0.0 hPa ;| difference is less Actual pressure loss 1.6 hPa s- Fud tank pressure toreraxe than two hPa. This means the EVAP D | i : i i i j i : i i i i i i i : i i -9 system has passed -to the leak test and -18 i i • • • : • • • • • • 1 -* • -20 should pass the •28 j j t" 1 monitor as the •30 > S 10 18 20 25 30 39 40 49 SO 55 60 63 70 78 SO 85 90 93 vehicle is driven. TCTB [S| si 16 Mercedes-Benz StarTuned
  17. 17. ^^3METALLI?t , usaiysa Km % Like Chip Foose, BASF Brings A Little Extra To The Party. lll»15iI»M:|lfr^iI^llYMVillll^ll(ll»k1t:to^l^ nas oeen doing tne same witn its unique color management system, ie< COLOR-MAX®, the industrys most precise color matching tool. The paint-sprayed chips of COLOR-MAX ensure a perfect match the first time, every time, reducing comebacks and increasing productivity. And BASF Refinish coatings are approved by Mercedes-Benz and most major OEMs across North America. Beautifu :ia™fflM«i<(iiii:|eu^>--Ji|KfcajS^^||^Emm^ forov tfa: •*) t JjKt.*-a i •
  18. 18. As Good18 Mercedes-Benz StarTuned
  19. 19. Chemical ccnding through the use of structural a collision. Automakers are now aware that the mix adhesiyesis not new to the collision industry, but of material choices used to manufacture a vehicle the need for repair professionals to keep pace requires adhesives that were formulated to match with advanced adhesive materials, equipment, the materials being repaired. £nq procedures is now on the front burner. Goingp | p r c , khe repair of Mercedes-Benz body panels Modern adhesives are more crash resistantf ^ ^ t i i i e r components demands a commitment to -Applying adhesive is a more complicated process^p(firu":g :e?rring about bonding techniques and than just slathering on some glue and clamping practices, its also an opportunity. the parts together. Modern automotive structural adhesives are made from chemicals called epoxies, Advanced adhesive f o r m u l a t i o n s which typically come with two parts, a resin and •]are. available a catalyst that are kept separate until used. When -Structiurs adhesives are not new; theyve been combined during a repair, the catalyst initiates apBtefrcnone than 25 years in the automobile chemical reaction in the resin. Expect to feel theli|gstf?y. Early adhesives were of the single- bonded parts heating up as the resin develops its component variety, which at that time was sufficient bonding properties and the mixture cures. for some.irepairs involving conventional mild- s^eiigjiksteeis. These yielded to two-component —The two-stage structural adhesives in use today^aplsh-e formulations that provided improved include polyurethane epoxies, glassy matrix||™feTg,.proDerties and allowed more working time. epoxies (which have glass beads embedded in the , •v Sty resin), and rubber-based epoxies. Glassy matrix That was f ne until the materials that vehicles were epoxies are extremely strong and rigid, and they (iriajMactiuiied with began to change in response resist shearing stress - the lateral separationJjljterna^cs for lighter weight, more rigidity, better of the bonded parts - at very high force levels.| f | t e g and environmental performance, improved Polyurethane epoxies are more flexible and provideS ^ . , a r i i d f lower manufacturing costs. To stop the a better fit for some components, but they break ever-inereasii g mass spiral without penalizing safety under shearing forces at much lower force levels,andcopfort, automakers have transitioned from than glassy matrix epoxies. Newer rubber-based ln^j^ifnilcjtensile-strength steels to lighter weight, adhesives contain additives that allow synergisticMi stronger materials, such as higher-strength rubber toughening of adhesives to provide high- steels, ofr-er metals (aluminum, magnesium, strength epoxies with greater flexibility - a hybrid of titanium, etc.), thermoplastics, carbon fiber- earlier formulations.K]|fereed plastics, and other composites.iS/^i.Vffji;•.:;;. .,-.#••• :i< , —The curing ability is built in to the adhesive, butijKli •;i S-*sW-"/:i1:Sv. "^J; V i ;:•:•.-. • -This;omgoing evolution is driving the increased use it requires a lot of testing and some impressivegfe|!ewica1 bonding (using structural adhesives) as chemistry to meet an automakers specifications. she preferred dnd recommended joining method, In some cases, curing may be aided by baking orSlfffif£ than welding, riveting, or other practices. some other procedure involving applied heat. SomeiMa^afnel [repair instructions, for example, epoxies even cure with the application of ultravioletSpfehoply, prescribe chemical bonding procedures light. Note that the curing times for various (that -use aMesives. adhesives can range from just a few minutes to a day or even longer. Automakers know their vehicles, -But challenges exist for adhesives (as they do so following their collision repair procedures ifpfiptteii Technologies). The reason: High-strength and using the approved resources ensures that||W^.i3,Ndy5».and plastics come in different grades, technicians have adequate working time to effect a: wrijehiiiimpacts how each material performs under- safe, complete repair. various stresses during normal operation and during February 2012 19
  20. 20. As GOOD As NEW—For example, some repairsmay only require a two-stage STRUCTURAL BONDING I RAMPING UP Sadhesive, while others mayrequire the use of adhesives 140and rivets - a process known 1 2006as rivet-bonding - or the O 120 / /combination of spotwelding.Technicians should note that 100 /repairs involving aluminum 1 -I a. 2004should use aluminum rivets, 80 /those involving steel shoulduse steel rivets, and that a 1 £ I s 2002 60coating of zinc dust to preventcorrosion may be required. Be osure to use the number of rivets I 40 0)specified in Mercedes-Benz 2 1997 |service information. 9n i l i • i • " 1996 1998 2000 2002 2004 2006 Year (Source: Dow Automotive)Chemical bonding Beginning in the mid-1990s, structural adhesives usage began to accelerate. Inprovides stronger and 1996, for example, approximately 35 meters of adhesives could be found in a nev/ Mercedes-Benz S-Class model. By 2006, the S-Class had over 135 metersmore durable repairs present. Its continued to grow since and this trend is prevalent in other Mercedes-—While based on earlier Benz classes. (Image — Dow Automotive Systems)two-component structuraladhesives, newer adhesivesalso include advanced specialpolymers, epoxy resins, adhesion promoters, and -Reduces the number of welds that would haveother additives that improve bonding, manage otherwise been required. For example, Mercedes-stress more effectively, provide better mechanical Benz requires OEM rivets and OEM structuralproperties and resist corrosion when compared to adhesive to be used in areas that squeeze-typealternative joining technologies. resistance spotwelding (STRSW) arms cannot access, or when replacing USIBOR (boron) - According to several industry sources, these components. Adhesive bonding is also a well-newer adhesives provide a number of advantages. known complement to help resolve problems withDow Automotive Systems and 3M note that using cracks around spot welds occurring as a result ofthe new two-part adhesives and procedures fatigue loads.recommended by Mercedes-Benz for chemicalbonding repairs: —Allows the various stresses during vehicle operation or a collision to be more evenly^Provides more durable and stronger repairs distributed across a region that is joined withwith less corrosion risk than welds alone. In fact, adhesives compared to those joined only by welds,adhesives usually form a bond stronger than the rivets, or other joining methods.materials theyre bonding together. In the future, ascarbon composites are increasingly used, adhesives —Enables the flow of energy force transferred inmight be the only way to bond them, as carbon fiber an accident to remain truer to the automakerspanels cannot be welded together. design intent.20 Mercedes-Benz StarTuned
  21. 21. STRUCTURAL BONDING BENEFITS High Rely on other joining Replication mode techniques in addition to Down gauging of sheet metal c/> o> / A adhesive bonding components Early adopters of technology, • - .c_ L Reducing no. of spot welds •4— move cautiously <D "O Investigating innovative ways c c Have not established to reduce total system cost 5 o CO QQ implementation strategies Optimizing joint designs 5 « "- D Use adhesives to enhance Primary use adhesives for lized truct corrosion resistance stiffness and durability improvements Use adhesives in areas where (0 0) welding or other joining Have not recognized the o> ^. options are limited benefits of fully fracture cc o • toughened adhesives Structural adhesives not • aligned with long-term strategies Low DD High Technology Acceptance (Source: Dow Automotive) The shift in the acceptance of chemical bonding technologies by automakers is leading to the realization of many benefits, some of them unexpected surprises, such as the opportunity to use thinner body panels without sacrificing performance or safety. (Image — Dow Automotive Systems)—Facilitates the down-gauging of metals (e.g. thinner components without compromising strength, safetyand lighter body panels, less steel reinforcement) for or durability.lightweight, optimized vehicle construction. —Adhesives also enable hybrid sandwich—Replacing otherwise necessary sealant materials construction to be employed in manufacturing. Forwith adhesive not only seals out water, it also instance, the front flexural and supporting structureimproves noise, vibration, and harshness (NVH) in some models (e.g. CL) is a load-bearing assemblyby dampening airborne noise distribution and made of carbon fiber-reinforced plastic sandwichedminimizing body vibrations. between aluminum sheets. "Improves the structural integrity during side- -It is important that adhesives not be theimpact IIHS tests. weakest link when joining adherent surfaces or components. Modern bonding adhesives provide- E m p o w e r s the introduction of lighter-weight acceptable or improved elasticity and flexibility, in carbon fiber roofs and other non-steel and non-alloy addition to better tensile and shear stress strength February 2012 21
  22. 22. As GOOD AS NEWthan the materials being bonded. Be cognizant and assemblies that are welded, riveted or bondedthat Mercedes-Benz employs different mixes of to the vehicle structure during the assembly/construction materials than other automakers during manufacturing process. Replacement of structuralmanufacture. In addition, just like different grades body panels/members/assemblies (clipping orof new and emerging steel can be used, repairers partial clipping) with recycled parts is unacceptableshould be aware that there are also different grades and not approved by MBUSA.of aluminum and other metal alloys, plastics, andeven carbon fiber. Mercedes-Benz collaborates with -Malfunctions caused by body repairs notadhesive manufacturers, such as Dow Automotive performed in accordance with Mercedes-BenzSystems and 3M, to develop structural adhesives specified repair procedures or otherwise not properlythat are best suited to their specific models and performed are not covered by the Mercedes-Benzrepair applications. These may or may not be the New Vehicle Limited Warranty and may cause the carsame ones required by other automakers. to not perform as originally designed in a subsequent collision to the repaired area.-MBUSA also has a number of position statementspertaining to body panels and chemical bonding —Consequently, it is critical that repairers knowadhesives. For instance: and use repair procedures developed by Mercedes- Benz, along with lists of approved supplies, tools—MBUSA does not support the use of critical and equipment. Hence, it is crucial that techniciansrecycled parts and assemblies, especially parts refer to Mercedes-Benz collision repair resources Need More Info About Using Adhesives? For access to Mercedes-Benz service information, technical bulletins, Workshop Information Systems (WIS) and more, visit http://www.startekinfo.com t subscription-based website. UHIMl.ink.ir.,11. www.mbcollisioncenters.com/pages/publicindex.aspx is accessible to Mercedes-Benz Certified Collision centers. Men nils Urn/ Certified i olllilon Program This website arms repairers in advance of what the composition of any part is before it is cut into - whether mild steel, high-strength steels and other metals, plastics, carbon fiber, or other materials. .._ —..—. .Mcrcn!»> IViu tVMmta I irti Finally, Mercedes-Benz provides access to archived StarTuned Magazine articles to collision professionals at w ^^•S ^ www.mbwholesaleparts.com/wholesale-parts/section/ jf lYlBEit startuned/archives, a website that allows repairers to L™,LMO STARTUNED search by year and date. For more information, use this V. (tics ET • »3> — link to access two earlier articles pertaining to the use _ _ ,__.._.......__ —. of adhesives in collision repair — When Welding Wont Do (May 2010) and Taking Stock in Bonds (December 2008). (Images -Mercedes-Benz USA)22 Mercedes-Benz StarTuned
  23. 23. tin accidents. Specific year/ TYPES OF STRESS model repair instructions can be found at the subscription- Tensile stress stretches Shear stress twists a based StarTeklnfo.com website. a bonded repair bonded repair laterally Be sure to refer to it and other MBUSA resources before beginning any repair. —For example, the new aluminum-body CL-Class uses aluminum panels as part of its load bearing structure. Outer body panels are constructed Compression stress Torsion stress wrings from aluminum, magnesium, shrinks a bonded joint a bonded repair and composite compounds. Aluminum is used for the roof, outer door panels, rear quarter panel, hood, and more. These new materials, such as load- bearing aluminum body panels, offer advantages. However, in Chemical bonding using MBUSA-approved structural adhesives, tools and many cases, standard welding procedures enables body panel repairs to better handle various type of stress methods cannot be used to compared to other joining technologies. The best place to use a structural join materials. Where welding adhesive is in a location where the primary forces are either compression (where is not approved for the repair, the joined pieces are pushed together), or shear, where the force tries to slide the chemical bonding provides joined surfaces against one another, like pressing your hands together and trying a viable alternative. In some to slide them apart Structural adhesives are typically not good to use if the force cases, Mercedes-Benz requires acting on the joint would pull the two pieces apart as most adhesives have poor a combination of riveting and peel strength. Another poor location for a structural adhesive would be one where bonding agents to maintain there are forces that would bend the joint which could allow the joint to cleave chassis strength. and then peel. In these latter two cases, repair procedures may specify that adhesives be used with rivets (rivet-bonding) or in conjunction with certain welding techniques. (Image — Dow Automotive Systems) —Lets consider a repair example where rivet-bonding is required. Here are some key noted in the Need More Info? sidebar. Otherwise, a considerations when making the repair: repair that looks fine cosmetically may in fact have durability and corrosion-related concerns, as well as Know the composition - Technicians less occupant safety should another accident occur must be aware of what they are going to cut in the future. into before doing so. MBcollisioncenters. com provides critical information regarding the construction of vehicle parts and An adhesive repair example: components. For example, various body Rivet-bonding panels on new models - roof, hood, —New vehicle construction techniques mean quarter, door, etc. - may be constructed of new procedures in collision repair to maintain the magnesium, aluminum, high-strength steels, integrity of a vehicle in the case of any following and even carbon fiber composites. February 2012 23
  24. 24. As GOOD As NEW Use the approved attachment methods, be ADHESIVES MAKE VEHICLES SAFER it replacement, welding of some type, or chemical bonding with adhesives — Attaching vehicle parts that are of two different materials should only be done if approved by Mercedes-Benz Chemical bonding using adhesives (illustrated in the SLSAMG diagrams above) using the repair procedures helps keep the absorption of energy forces during a crash truer to designed the automaker specifies. The load paths.The basic principle is to ensure mat the joining of adherents, at StarTeklnfo.com website is manufacture or after a collision repair, remains stronger than the adherents the best resource for specific themselves, so that the latter absorbs most of the unwanted crash energy, while information, especially the adhesive itself only absorbs a very small portion of this energy. the procedures laid out in (Image — MBUSA) the Workshop Information Systems (WIS). Different grades of carbon fiber -.•-JSC" ueSSSHSBBSS mm material require different chemical bonding procedures and/or agents. In addition, BE14414TE 2096 should dissimilar metals such as steel and aluminum The adhesive kit Betamate 2096 from Dow Automotive Systems is now available be joined, it is critical that (Part # A 009 989 36 71) and must be used for the repair procedures described repairers avoid any cross in all WIS which require body adhesive. The structural adhesive must also be contamination by working applied using the adhesive dispensing/metering gun for 2-component adhesives on the separate metals in (Part # W 220 589 03 63 00). In some cases, Zinc Dust Paint (Part # A 000 different areas and with 986 36 42) may be required tp prevent corrosion, (image — MBUSA) different tools. In addition, repair procedures such as rivet-bonding may be required rather than as thoroughly versed in Mercedes-Benz welding, as the latter could deform the vehicles - remember, its your responsibility metals and the interaction between the to make the full, correct repair - be sure metals may lead to premature corrosion to ask what the specific steel grades of the beneath repainted finishes. rivets and body panels are, and also whether or not any adhesives or other supplies you Source quality parts, fasteners and purchase meet MBUSA requirements. adhesives — When fastening body panels together, the use of proper fasteners is Cleanliness is essential — Clean surfaces paramount. To rivet-bond aluminum, be sure are required for proper bonding, just as to utilize aluminum rivets; to fasten steel they are for welding. It is also important panels, use steel rivets. Also, ensure that that bare metal be bonded to bare metal the rivet gun being used is strong enough and not painted surfaces. Repairers may for the job. Body panels, other parts, need to grind a body panel down to bare rivets and adhesives are available from metal by removing enough of the corrosion Mercedes-Benz or aftermarket suppliers. inhibitor layer to expose sufficient bare Because aftermarket suppliers may not be metal to assure a thorough bonding. Finally,24 Mercedes-Benz StarTuned