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Discussion Starter #21
Adaptive System Fuel Injection

An article I found whilst reasearching my problems

I've always loved the puzzle. Check Engine warning lights have become an everyday chore for me over the last five years. It's a challenge that extends my interest and creativity in the auto service profession.

Before I deal with some specific Mercedes-Benz faults that I've researched, I must say that the ability to really solve these puzzles in any car depends upon two important factors. First, and most important, is a working knowledge of the system involved and the specific nature of the fault that's been recorded. This means knowing what conditions must exist to set up the evaluation that failed, as well as the nature of the test that failed. The second factor is the nature of the tooling available for testing the criteria being faulted.

In a relatively short magazine article, I certainly can't teach the systems, but I can show a number of techniques that can change 70-80% of Mercedes Check Engine lights into money-making repairs, that will boost customer satisfaction in the process.

ADAPTION CAPABILITIES
Probably my favorite fault codes are the ones that deal with the adaptation capabilities of the system. In my CIS days, we (as technicians) centered the system so that electronic feedback control could work equally well correcting both rich and lean. In these cars, the adaptation fault codes were O2 sensor codes. The controller recognized when the O2 sensor was stuck at the rich or lean stop. Being stuck against a stop usually wasn't the O2 sensor's fault and the problem always boiled down to a mechanical mixture issue. With the change to electronic injector control (done to facilitate single cylinder cut-off necessary for future OBD II), the ability to center the mixture range was built into the software. In these first systems, LH and HFM, the diagnostic controls necessary for U.S. emissions control were not yet incorporated into the engine management hardware or software. These cars had their Check Engine light controlled by the diagnostic module (DM).

So, in the late '90s, we started seeing the first of the real fun adaptation codes on the DM. There's an M-B service bulletin applying to the Jacksonville Zone (I live 80 miles from Jacksonville, FL). It talks about the Code 19 Check Engine light and, while the concept of adaptation isn't mentioned, it says that a new controller is the solution. This code, if read from any simple description, blames the injectors. But the real problem is that the system has reached its adaptive limit. In the Jacksonville case with 119 model V8 engines, the lower partial adaptation and maybe the upper partial adaptation would bump against 0.85. This meant that the original fuel calculation of 1.00 had been reduced 15% to 0.85 under one or both of the measuring criteria. The way Mercedes repaired this problem was to increase the software's corrective capabilities. In cars that I've repaired with the new software, the mixture stabilizes at around 0.81 after two years (my oldest test case).

On all Mercedes vehicles with adaptation codes, it's necessary to reset the adaptation after repairs to the original 1.00 value. On the early LH and HFM systems, the relearning after such re-adaptations can take weeks and is not very usable to diagnostics unless you have a chassis dyno. For perspective, I want to explain a short research project I did on a 600SEL that had the estimate of both controllers to solve the Code 19 problem. The lower partial load correction was at 0.85 on one bank and 0.89 on the other. The upper partial was above 0.90 on both banks. At first, I readapted and drove the car. I gave it back to the customer, and it took two weeks to readapt to the point of setting the light. I finally put the car on the dyno and did the relearn using the aid of the scanner.

After doing the adaptation a few times, it became apparent why it took so long on the street. The program requires achievement of a certain condition: Load 40-80kg/hr; rpm 1,600-2,200. Once stable at that condition (easy to achieve on a dyno), the car's adaptation program goes active and it requires holding those conditions for maybe 10 seconds in lower partial. If you try to recreate these conditions on the road, it's almost impossible except when driving against exactly the right angle hill. At the load stated, the car accelerates unless it's on the right-size hill and quickly exceeds the rpm criteria, stopping the adaptation process.

We did a number of parts swaps, as the system on this 12 cylinder is actually two 6-cylinder systems. The swap that won was changing the air flow meters. We found that no matter where we put one of the units, we always got a 0.85 lower partial after the relearn. A new unit saved a bunch of money, for the moment.

For the moment, as Mercedes eventually found out, 15% was too little built-in correction, and all the cars since the ME engine management system have had 32% correction capabilities from 0.68 to 1.32. All replacement controllers for early LH and HFM systems also come with the new capabilities, solving the problem on early cars. You must recognize that the real problem in all these instances is that the mixture has changed from the standard. In the case of a 0.85 car, the system is subtracting 15% fuel to keep the range of correction in the center (remember what we did with CIS!). This brings me to the current, most common code going: The P0170/P0173 adaptive limits code.

ADAPTIVE LIMITS CODE
On the latest M-Bs, this most common code usually means one of two types of Air Mass Meter (AMM) failure. The first type, AMM failure, results in failure of the partial load multiplicative correction at 1.32. This means they are correcting a lean mixture by adding 32% more fuel to the original 1.00 calculation.

The second type of failure is more interesting. In this failure the output of the AMM is not linearly skewed as in the first. The partial load will probably be in the range of 1.10 to 1.20 or so. This correction is multiplicatively applied to all range of fuel control from cold start to idle. At idle, this AMM runs fairly accurately and, as a result, the Closed Throttle Position (CTP) additive correction has to repair the rich-running condition caused by the multiplicative correction. It does this with an additive correction of up to -1.0 ms (removing fuel). The limits of correction here are -1 ms to +1 ms.

Most of the P0170/0173 codes are on V6 and V8 models and AMMs are the common problem, but the two codes refer to right and left bank and they can be used to evaluate air leaks. One should always look to air leaks in cases of positive additive CTP corrections.

MISFIRE CODES
Leaving fuel adaptation, I need to make a small mention of another group of fairly unique Mercedes attributes in adaptation: Throttle and sensor ring. Mercedes uses something it calls sensor ring adaptation to compensate for regular deviations of crankshaft acceleration rate that appear at particular load and rpm blocks. This crankshaft acceleration rate is what is evaluated for misfire determination, so the adaptation is done to prevent driveshaft, flywheel, motor mount and other rhythmic vibrations from distorting this calculation. I suspect that many of the misfires of unknown origin come from mistakes the software makes in identifying a misfire, which then, of course, shuts down fuel at that injector, assuring there is a misfire until the key is cycled.

My wife may have had such a condition with her in-warranty ML320. She had a misfire on cold start nearly every day and would have to shut off the car and restart it to remove the misfire, and a misfire code would be set. It went to the dealer and the first repair was to readapt the sensor ring. This made the problem go away for more than two weeks. At the next visit, they replaced the ME control unit. I had looked at the load/rpm sensor ring blocks both before and after the new controller was installed, and the number of blocks was increased by at least three times from four to maybe 16 with the new software on the new controller. I believe that during the heavy, low-speed turning in reverse, the normal judder of early M-B 4WD was being misinterpreted as a misfire.

Throttle adaptation is one area that is fairly simple, but because M-B uses throttle control for idle control, cruise control and drive-by-wire, it's very important when evaluating any of these problems to be sure that the throttle is adapted. It's a PID on most scanners and is also a menu item under adaptations of most scanners. All that is necessary with most scanners is to erase the old adaptation and relearn with the key on and engine off for 30 seconds, followed by the key being switched off for 10 seconds.

There are a number of simple things to look for with Mercedes misfires. My first advice is to be sure no one has erased the adaptations on one of those P0170 cars. When they lose that 1.32 adaptation and then run at 1.00, they will set random misfire codes. Remember that most specific single-cylinder misfires (P030x) are caused by the resistors at the spark plugs, including the ones located below coils. They can be so common, intermittent and hard to view with a scope, that we've started replacing the three beneath the coils (p/n 000 156 36 42) when changing spark plugs on HFM motors (see Fig. 1). We see plenty of coil problems and usually achieve a diagnosis by moving the coil to another cylinder.

The P04xx group of codes probably are the gravy of the emissions business. From EGR, to secondary air, to evaporative emissions control, these codes represent the testing of emissions systems that mostly have no driveability performance effect. These are the codes the customers hate. In my small window on the trade, it appears that the pieces designed to do monitor tests are not designed to perform as the safety and hardware items have been. Most of these codes are for failing two tests over time. The tests are often run only once a drive cycle, so it takes a while for them to get run and, thus, the light can stay off for long periods of time with the problem still existing.

All of these fault codes are best tested with the activation programs built into proper scanners. In the case of EVAP codes P0440 through P0455, Mercedes uses a vacuum-style test of the system for vapor leaks and current supply calculations from internal dropping resistors to evaluate solenoid control. In normal operation, the engine controller pulses the purge valve in varying amounts, pulling air over the fuel vapor absorbed in the charcoal canister, moving it into the engine for burning.

To evaluate the system for leaks, a cap is placed over the charcoal canister air inlet and a vent valve placed there is closed. Closing the canister seals the system, and the subsequent opening of the purge valve allows the tank system to be placed under a small vacuum. The test for this system is straightforward with the help of a scanner. The scanner needs to interpret the tank pressure and be able to close the vent valve. When run by a scanner, you are told to pull no more than 25 millibar (mb) on the system and then watch the decay over time. It can't drop more than 5 mb in 60 seconds.

I built a tool based on this design that's posted on iATN (see Fig. 2). Based on a 5V-powered GM tank pressure sensor, we made a connection through a new gas cap (see Fig. 3). I built this tool because even though M-B scanners will use a manually run test, BMWs and Volvos use a forced monitor with pass/fail results. In these cars, the test is run and, if it fails, there are diagnostics. But if it passes, you have no help. The tool allows you to watch what is happening during a forced monitor or a manual one such as what M-B uses.

In Fig. 4, we have a graphing multimeter record of a manual test we performed on a SLK230. The first ramp is the period where the vacuum is created in the tank. It is pulled by a hand vacuum pump at the purge line to 25 mb, as determined by the scanner (see Fig. 5). The peak is 25.4 mb. At the peak, the hand pump has stopped and the leak criteria is that the system must not leak more than 5 mb in 60 seconds. The increased leak rate slope starts when the scanner reopens the vent valve. At that point, the scanner had 21.3 mb. From the graph, you can see that the time interval is well over 60 seconds and the drop is 4.1 mb, which is well within the criteria.

In the second graphing multimeter image (see Fig. 6), a 0.040-in. hole has been drilled into a piece of hard plastic vacuum line placed between the hand pump and the purge line. It was originally covered with tape and the vent valve closed and the system hand- pumped to a little over 25 mb again. The small down slope is the natural system decay, and the larger slope is after the tape is removed. The slope of the line now is way beyond the failure spec of 5 mb per 60 seconds.

This imaging gives a context to the testing of small leaks. The testing of large leaks is very seldom an actual leak. The car looks at the upward slope as in the GMM images. The slope of that section depends on the rate of hand pumping in these tests. When the car runs the test, the test value must be achieved in a certain time. If a leak is too big, then the pressure in the tank never rises or rises too slowly. The SLK we were testing had a large P0455 leak code. The problem was that the line coming out of the charcoal canister to the tanks was plugged. There was no leak but, because the tank never saw the vacuum that was applied, the assumption was made in fault analysis that all of the vacuum had leaked rather than make it to the tank. We've also found the purge valve itself to cause large leak codes due to being plugged with charcoal or not opening at all.

While working on the SLK, we used our new toy to mimic another uniquely Mercedes purge test. This test is not used on the SLK, but we set it up for view. On many mid-'90s cars, M-B had both an Air Mass Meter and a MAP sensor installed. During purge testing, the MAP sensor was shunted to the purge line from manifold vacuum by a switchover valve. During purge, the controller looked for pulses on the MAP signal in frequency with the purge flow duty cycle. In Fig. 7, we've mounted the GM tank sensor tool into the line after the purge valve and the output is channel 2 on the scope pattern. Channel one is the signal to the purge valve (see Fig. 8). This mechanism for faulting the purge valve is used on 202 models with HFM and 129 models of ME, using 104, 119 and 120 motors and maybe others.

TESTING FOR OTHER CODES
Secondary air codes are another type of code made simpler with the use of a good scanner. Secondary air injection is used for burning the rich mixtures of cold start and for heating both the O2 sensors and the catalyst. They have to be shut off before closed-loop fuel control can take place. M-B uses an intrusive test with the O2 sensors to evaluate the "causal chain" of secondary air. Causal chain is a M-B text term that baffled me for a time. I've now come to the conclusion that this phrase means that a fault in causal chain means that everything necessary for a result to happen, happened, but the result didn't happen. In the case of secondary air injection, it means that the air pump was turned on and the check valve was directed open, but nothing happened.

To make this evaluation, the car and scanner causes the air pump and check valve to work on a car in closed loop and the O2 sensor voltage must reach either 80 mV on early cars or 40 mV on later cars within a certain time span. I used my scope to verify such activity on a 1999 E320. I did cheat and use the scanner for activation, but I backprobed the O2 sensor for the output. I swear this is a real scope pattern of the test (see Fig. 9). It almost looks too perfect.

Most M-B problems with secondary air originate in the vacuum controls and sometimes the electrical components of the pumps (including clutches on belt-driven pumps) and weak O2 sensors. The real nasty ones are the restricted passageway causal chain codes. These are happening mostly in 119 engines.

A quick way to determine if the reduced capability of a system is O2 sensor or secondary air flow-related, is to first run the test above. If you get only a drop to 100 mV before fuel correction moves it back up, try as a second test to monitor the O2 sensor and crack the line to the brake booster. With a good sensor, the value will pass the 40 or 80 mV criteria, without even making the car run bad when the vacuum line is cracked.

At this time, I haven't heard of any way to clear the restricted secondary air passages in 119 heads except by head removal, making this the all-time most expensive fault code for a failure of a non-performance test.

EGR codes are fairly simple on most M-Bs. They are often vacuum control problems, but most commonly the pipes that carry the EGR into the intake get clogged. One interesting note about these clogs is that the clog is not from EGR gasses. The clogs come from oily PCV vapors in the intake baking onto the pipe carrying the EGR gasses. So when looking for the restriction, start at the intake end. On 104 motors, this is the common place (see Fig. 10). On 112 and 113 motors, there is a stainless pipe that enters the intake in the middle rear. It must be removed and then can be easily cleaned.

A proper scanner again gives the basics in testing through activation. If it activates with noticeable motor effect and still sets a code, the chances are high that the line is restricted. One can do a similar test by teeing into the vacuum to the EGR and driving. EGR will take place at most throttle settings other than closed and full. Once vacuum control is verified, a vacuum placed on the valve with the engine running at idle finishes the effect of the scanner test. If it passes both tests, and still sets a code, look to the pipe.

There are lots of other codes but space is short, so the last code I want to talk about is another strictly M-B code. It is the upshift delay codes P1700 and P1701. These codes would only apply to the mechanically controlled automatic transmissions used before 1996. Those transmissions used a throttle pressure cable (control pressure) for determining shift points under various loading. In order to heat the CAT and reduce the cold running time, Mercedes used an electrically controlled, vacuum-operated bellcrank-type lever action to change the capabilities of the control pressure cable. In other words, when cold, vacuum at the switchover valve is switched to a vacuum chamber at the transmission end of the shift cable. There, the actuator movement changes the effective length of the cable. The common problem here is the diaphragm in the actuator element, but testing is simple.

The first test is to see that vacuum is at the switchover valve when running. Next take the line to the transmission from the switchover valve and apply vacuum. In the common failure, the element won't hold vacuum, and you're done with diagnostics.

If the vacuum element holds vacuum, then you must tee into the line at the element and evaluate the vacuum when cold. If there is vacuum at cold running, and a code is present, then evaluate the shift against the criteria. The element is adjustable on the replacements and the cable is always adjustable. A poorly adjusted shift cable adjustment could make the added shift delay not large enough to satisfy the controller.
 

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Discussion Starter #22
Instrument Cluster Tests

IF you need to run Instrument cluster function test. To do it start engine, then press small button in the center of clock adjusting knob (not the knob itself) for more then 5 seconds. You'll need something like a sharp pencil to do it.
The first test will appear on the outside temperature display. It will read something like 35.1, were 35 is gas in the tank in liters and 1 is the number of the test. To advance to the next step pull the clock knob and turn it clockwise.
There are 9 steps:
1. Gas in the tank in liters
2. Momentary fuel consumption 34.2 is 3.4 liters per hour 2 is step number
3. Engine oil pressure in bar 20.3 means 2.0 bar step 3
4. Engine rpm x 1000
5. Engine oil level 0.5 is OK, 1.5 not OK
6. Activation of the oil pressure, fuel consumption, and fuel tank gauges - needles in the first quarteer of the dial. Indicator 0.6 for step 6
7. Activation of the oil pressure, fuel consumption, and fuel tank gauges - needles in the second quarteer of the dial. Indicator 0.7 for step 7
8. Activation of the fuel consumption, and fuel tank gauges - needles in the third quarteer of the dial. Oil pressure gauge stays in the second quarter. Indicator 0.8 for step 8
9. Activation of the fuel tank gauge, needle in the fourth quarter of the dial, oil pressure remains in the second qurter, fuel consumption remains in the third quarter. Indicator 0.9 for step 9
Done
You need to verify oil pressure reading in step 3 and gauge in steps 6...9
 

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Discussion Starter #23
HorsePOWER

The first thing to remember is that BHP is not measured on a dyno - only torque, BHP is a factor of torque and engine speed - its just a theoretical calculation

First, power, what do we mean by that?

Well, we usually express power in terms of the amount of time it takes to do a certain amount of work... for example, one horsepower is measured as the amount of work required to lift 33,000 lbs over 1 foot in 1 minute (huh -that's obvious, _). As this is such an obviously Scottish measurement (as James Watt first devised the calculation) , we have a metric equivalent... the metric horse could lift 4,500Kg a metre in a minute... 98.6% of a good British horse. The Europeans decided to call it a PS (Pferde Starke - German for Horse power&#33instead of an HP to cover their shame. Also, in the newfangled metric system, 1hp is the equivalent of 746 Watts of electrical power. So, to recap briefly:

1 HP = Roughly the amount of work a horse can do lifting coal up a mineshaft, assuming his heart was really in it = 1.014 PS = 0.746 KW - easy huh _

Now we need a way to measure this output - so we use a defined force or "brake" to see how much energy we need to apply to stop it - Hence "Brake Horsepower" - and is defined as it's maximum performance at a certain rpm.


The other thing we babble on about is Torque... Torque is the amount of force applied to turn something multiplied by the distance from the axis of it's rotation... sounds all weird, until you realise that we use the engine to rotate the front wheel, so torque is something that would be nice to calculate. Something interesting is that 1hp is 550ft/lbs of torque per second.

Now, it's fairly easy to measure torque... this is where the dyno comes in, and we calculate horsepower from an engine's torque output multiplied by the revs...


A dynomometer is just a heavy drum (brake), an accelerometer and a computer... if you know the weight of the drum, and you know how fast it's being accelerated, you can calculate the torque that must be being applied to the drum. What you also want to take into account are the frictional losses on the drum, and the air temperature at the time (which is why you'll see air temperature, pressure and a correction factor calculated by the software... as air temperature goes up, so the effective power output goes down, so the correction factor has to go up to normalise this).

Taking a Dyno Run
( As used today at PTS - differs slightly if they use an inductive loop)

So, to measure torque, we strap the car to the dyno, start it up and run it up in the gears to 3000RPM the dyno operator holds the car at a steady 3000 for 6-7 seconds and the dyno learns the road speed for that car at 3k. ( Some dynos use an inductive loop to accurately measure RPM - but the rev counter method works fine for most modern cars) - now with a given road speed the RPM can be calculated.
... cars tend to do their power runs in 4th gear, as it's the best gear for acceleration at speed and less chance of the wheels slipping, as the calculation errors get smaller the bigger the numbers are. 4th is used because on cars these days 5th gear tend to be a bit of an overdrive.
The throttle is gently floored, and the dyno slowly allows the speed of the engine to increase - this measures the torque of the engine. When the engine reaches maximum RPM, the operator puts the car in neutral, and allows the wheels to decelerate of their own accord - this measures the losses of the transmission,driveshafts,bearings brakes (if they are sticking) and tyres

Now here comes the maths

BHP = Torque (lbft) x RPM
_ _ _ _ -------------------
_ _ _ _ _ _ _ _ 5252

This means that BHP is always equal to torque at 5252rpm _- if its not then there is something wrong!

Now using Pauls results from today we get max power of 169.3BHp @ 7869RPM but 115.0lbft of Torque. The important factor here is that it makes its maximum power at nearly 8000rpm!

Andy Blower made more torque 123.5lb/ft - therefore it must be quite a bit more powerful right? - WRONG ! - he made his max figure at 7309rpm - and as BHP is proportional to speed and his engine was making its torque at a lower RPM value - he gets 169.4 BHP - a whole 0.1bhp more _

Shirish made 129.8lb/ft at 7466rpm - which equates to 170.4BHP

So now we have 115, 123.5 and 129lb/ft of torque - all at different engine speeds - All giving an output of 170BHP give or take a little bit

The moral of this essay is - it is better to make torque at high RPM for a screamer! - and thats why beause Hondas rev so high they produce the power!

I realise I've forgotten an important part of the calculation _

Where did the 5252 figure come from ?

As discussed what we actually measure is torque, expressed in ft/lb, and then we calculate actual horsepower by converting the twisting force of torque into the work units of horsepower.

Visualize a one pound weight, one foot from a fulcrum on an "invisible weightless" bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (pi times a two foot circle), and, we have done 6.2832 foot pounds of work.

OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per revolution of the weight into 33,000 foot pounds, we come up with the fact that we have to rotate that weight at the rate of 5,252 revolutions per minute in order to do 33,000 foot pounds per minute of work, and thus do work at the equivalent rate of one horsepower.
Therefore, the following formula applies for calculating horsepower from a torque measurement:

Horsepower = ( Torque * RPM ) / 5252

Thats where the 5252 comes from


Torque is only half the story. While torque is the force created, it doesn't account for the importance of revs.
Imagine trying to remove a wheel nut from a car with a standard wheelbrace and all the torque you could produce can't loosen the "Kwik fit special" airgunned super tightened wheel bolts. You apply lots of force, i.e. torque, but you still can't generate any rpm. Therefore nothing is accomplished, no power generated despite your cursing and kicking. So - Without rpm, torque is useless!

Two engines may make 125 foot/pounds of torque, but if one is a FixOrRepairDaily turning at 5,000 rpm and another is a Honda turning at 10,000 rpm, the Honda is doing more work than the FixOrRepairDaily, therefore generating more power.

HP = Torque x RPM / 5252

so the FixOrRepairDaily makes 125*5000 / 5252 = 119HP,
but the Honda makes 125*10000 / 5252 = 238HP_
 

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Discussion Starter #24
Key Pro-game-ing..??

19/97-4 GROUP 82 - MODEL 140, INTRODUCTION OF ROLLING
CODE UNIVERSAL TRANSMITTER: As of vin # A367861 with production
date of 03/27/97, all Model 140 vehicles are now equipped with a garage
door transmitter which is capable of functioning with rolling code garage
door openers. The new style transmitter can be identified by amber
LED's as opposed to red LED's on the previous version. The
programming procedure has also changed, and is listed below. A
Service Information on this topic is being prepared and will be released
shortly. PROGRAMMING THE UNIVERSAL TRANSMITTER: 1) Prepare
for programming by erasing all three factory defaults by holding down
the two outside buttons until the light begins to flash (20-30 seconds).
Release both buttons. 2) Hold the end of the hand-held transmitter
against the universal transmitter keeping the light on the Universal
Transmitter in view. 3) Using both hands, push the hand-held transmitter
button and the desired button to be programmed on the universal
transmitter. Hold down both buttons until the light on the universal
transmitter flashes, first slowly and then rapidly. When the light flashes
rapidly, both buttons may be released. (The rapid flashing light indicates
successful programming.) 4) Repeat steps 2 and 3 to program the
remaining channels (if necessary).
If after repeated attempts, you are unable to successfully program the
transmitter, the garage door opener may be equipped with "rolling code"
security. This can be established by either of the following: a) The
hand-held transmitter appears to program the universal transmitter, but
thereafter the vehicle's universal transmitter does not activate the garage
door. OR b) The garage door opener was manufactured after 1995. To
train a garage door opener receiver with the rolling code feature, follow
these steps (the aid of a second person is suggested): 1) Locate the
training button on the garage door opener receiver (this is the opener unit
itself). Location and color of the button varies by manufacturer.
Reference the garage door opener manual or call 1-800-355-3515. 2)
Press the training button on the garage door opener receiver until the
light next to the button begins to flash (1-2 seconds). 3) Press the
programmed universal transmitter button in the vehicle until the training
light on the garage door receiver turns solid (1-2 seconds). Release the
button on the universal transmitter, and then re-press which turns off the
training light. Confirm the operation of the garage door by pressing once
again
 

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Discussion Starter #26
Self leveling

IF your ADS system might be a little slow to respond some of them are if they are not used often or they have switched themselves off to protect things... when you have filled with clean oil try lifting the back from the diff housing with a trolley jack,so tyres just touching floor(do this on flat surface)whilst running engine and switch ADS on and off a few times.. then drop and lift a few times.5times front each side 5times back switching between hard5 and soft5. check the colour of the oil.. and the magnet in the reservoir .. see if you have muck.. will flush system round a bit give it somthing to do..last time should remain HIGH for some time and settle slowly..then you can do the trunk test.. get two of your larger friends to climb into the back and watch to see if the self levellig system takes you back to level again..should be less than 30 seconds and then if the ride seems a bit harsh to start with.. It might just be it needs to re-learn what to do.. If you have no lights on then I would give it a couple of hundred miles to sort itself out.. then see if you need spheres etc..
 

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1997 S600 (sold)
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Getting to know your closing assist pump: function, tips, and fixes.

Getting to know your closing assist pump: function, tips, and fixes.

I. Introduction

If you’re reading this, you must be having problems with your closing assist system. Probably it doesn’t work at all. You may have experienced the slow door by door failure that many seem to report. One door stops working. Then over the course of a week or so, all the doors and the trunk stop working one by one until eventually nothing works. Before you let a less knowledgeable person convince you that you need a new pump (about $400 right now), allow me to see if I can convince you otherwise.

Before I say more, one of the best things I did was get a subscription to www.alldatadiy.com for my car. It’s a very well-spent $25 for the first year and $14/year thereafter. Alternatively, you can purchase a W140 manual CDROM from various sources for $150-$200. I have both, and I have found that alldata has had everything that I’ve looked at on the CD so far.

I bought my W140 (1997 model S600 sedan) knowing that the closing assist system was not functioning. Some posts on this board got me started in the right direction, but I learned more than I expected as I dug into the problems with my system. I’ve been able to breathe new life into my pump and return my system to 100% reliable operation for almost a year so far. This document compiles my expertise gained from troubleshooting my own system and from helping a couple others on the board do the same over the last few months.

There are two air pumps onboard your W140, the pneumatic system equipment (PSE) pump (also referred to as the central locking pump) and the closing assist pump. The PSE pump performs several functions including locking/unlocking of doors, inflation of lumbar support bladders, operation of reverse antennae on the earlier cars, extension and retraction of the trunk handle, release of the trunk striker eye for auto-closing, and providing vacuum to the vacuum reservoir when the car is not running. This pump is located under the rear seat on the passenger side. The closing assist pump is involved only with the auto-close function of the doors and trunk lid. It is located in the trunk.

II. Accessing the Closing Assist Pump

The closing assist pump is simply crammed into a foam cube tucked between the left rear fender well and the gas tank. You must remove the trunk liner on the left side, and it helps a lot to remove the liner piece at the forward wall of the trunk. It is possible to just bend the corner down to get the pump out, but access is much easier if you remove the whole liner. It only takes removal of a few more of the plastic push rivets. If you have a CD player, you must remove this first in order to remove the left side liner. It’s easy: 2 screws and one electrical connector. If you don’t see the pump at first, follow the bundle of red plastic air lines.



Just pull the pump out. The lines are labelled with initials which, I believe, are short for German. VR = vor rechts = front right door. HR = hinter rechts = rear right door. VL = vor links = front left door. HL = hinter links = rear left door. HD = not sure = trunk. SK = not sure of this one either = pump outlet line, hooked up to nothing.



III. Pump Function

Understanding how the pump functions is central to identifying any problems with your system. The heart of the pump is a sizeable electric motor that directly drives the air pump. What is neat about the design is that the pump can both pull a vacuum or develop pressure on any of the door or trunk lines independently and at the same time. That way only the door or doors that need it get pulled closed. This is accomplished by electric solenoids that switch each line between pressure and vacuum. The solenoids are controlled by the pump electronics which receive signals from microswitches in the door latches and trunk latch telling the pump that a door has partially closed and needs to be pulled shut.

The pump does the closing of the doors and trunk with pressure. It pressurizes the lines causing the extension of pistons in actuators, which in turn move levers in the various latches, which pull the doors or trunk closed. The pump runs until one of two things happens: 1. It reaches a pre-set shut-off pressure (at which point the pump "thinks" it has properly done its job of closing the door or trunk), or 2. It never reaches its pre-set shut-off pressure and then runs for a set amount of time and turns off (that is, it "times out"). After pressurizing the line and doing the auto-closing, the pump then pulls a vacuum on the line, presumably to ensure retraction of the actuator piston. The pistons are spring loaded, but I suppose occasionally, they may not retract fully when the pump releases pressure.

Case 2 is where a lot of problems arise. If the pump times out twice on the same door or trunk line, the pump electronics permanently turn off function for that line. That’s just the way the system is programmed, and it’s usually why just one door stops working. The pump specifically turned off that line because it timed out twice. Back to why the pump timed out… because it couldn’t reach the pre-set shut-off pressure. Why couldn’t it reach its pre-set shut-off pressure? Two reasons: 1. Because an air leak has prevented build up of enough pressure or 2. Because the shut-off pressure is set too high. So the course of action is clear. If you don’t have an obvious air leak, you’ll want to address the shut-off pressure. The pump has a pressure sensing shut-off switch which is adjustable. The following troubleshooting section will show you how to reduce the shut-off pressure on your pump thereby preventing the pump from timing out and shutting down on its own.

This very simple adjustment completely restored reliable function to my system. Hopefully, it can for yours, too, but there are many other failure possibilities, which I’ll discuss in the next section.

IV. Troubleshooting Your System

Note: Be careful when removing the air lines from the pump. I used a screwdriver to pry them off and had no problems, but I know that others have broken off the nozzles, which may force you to buy a new pump. I don’t have any hints for easy removal of these lines.

a. Bringing Your Pump Back to Life

There are two reasons why a door may fail to close. Either your pump is not working, or your pump is not getting a signal telling it that a door has partially closed, i.e. the microswitch is bad or out of adjustment, or the wiring from the switch to the pump is bad. Most likely, it’s the pump that has shut down. First thing to do is to try pulling fuse 9 in the trunk fuse box. Pull it out, wait several seconds and replace it. This fuse is labelled for the closing assist pump. Try a door or the trunk to see if the pump turns on. Some have reported this works to bring their pumps back to life, but this never worked for me. At this point, pull out the pump as shown above and remove the electrical connector on the pump and replace it. Completely cutting power to the pump resets the electronics so that it will again operate all lines until the two time-out thing starts happening again. If you do nothing else, your pump may work for a while, but will again eventually shut down because of the same reasons that caused it to time out in the first place.

If your pump comes back to life, congratulations. You very likely don’t need a new pump. If it doesn’t, I probably can’t help you. Perhaps the electric motor has shorted out. It works hard and gets hot very fast inside the pump housing. Or maybe the brushes have simply worn out. It may be possible to replace the brushes, but I don’t know. If you’re electronically inclined, maybe you can tackle the problem. There is also a printed circuit board inside the pump. Plenty of components can fail there, but I cannot address this.

If you have a door that works intermittently (sometimes a door works and sometimes it doesn’t, seemingly at random), your problem may be a microswitch issue. Sometimes the microswitch gets tripped and sometimes it doesn’t when you close the door. Intermittent function is never a pump issue. Once the pump shuts down a line, it’s off for good (until you completely electrically disconnect it by pulling the connector).

Once you have the pump on your trunk floor, you can observe the two time-out then shut-down behavior of the pump. Disconnect the trunk line (HD) and leave the nozzle open. Now, simulate the closing of the trunk by operating the catch in the lower trunk latch with your thumb. The trunk lights will turn off, the trunk handle will retract, and the HD line will hiss loudly with air pressure from the pump. The pump will run for around 10 seconds and then stop. All seems well. Do it again. All seems well. Do it a third time, and nothing will happen with the pump any longer. Unplug the electrical connector and plug it back in. Simulate trunk closing again. All back to normal.

Now, check your pressure shut off mechanism. Put your thumb firmly over the HD nozzle preventing any leaking, and then simulate trunk closing, the pump will start up, and it should shut off almost immediately. That is because it pressurized the trunk line, and with your thumb over the nozzle, it reached the shut-off pressure very quickly and turned off. You can repeat this indefinitely. As long as the pump reaches its shut-off pressure and doesn’t time out, it operates just fine. If your pump doesn’t shut off when you do this, you’ve got a more serious problem with the pressure shut-off switch.

b. OK, My pump works. Now what?

Leak checking is next. As mentioned earlier, air leaks will cause the pump to time out because a leak may prevent reaching the shut-off pressure. There are a couple of ways to find leaks. You can use a pressure device with a gauge (mityvac or similar) to pressurize the line in question and watch for leak down. There are specific Mercedes factory specs for leak down. I don’t know what they are, but it is on alldata. Alternatively, you can simply operate the door or trunk once you’ve reactivated the pump and listen carefully for the telltale hiss of a leak. The pump really moves a lot of air. I believe that any leak large enough to prevent the pump from reaching the shut-off pressure will be audible. Just listen.

There are myriad opportunities for leaks. Lines can separate inexplicably from connectors. Lines can get pinched and crack. Lines can get chaffed and worn through. The actuators are also a source of leaks. These have rubber o-ring seals that can get hard and crack with age. There may also be leaks internally inside the pump. These may be fixable or maybe not. More on this later.

One boarder (beelootin) contacted me recently when his trunk stopped working followed by everything else. After he found his pump was fine, his mechanic turned down his pump’s shut off pressure per my instructions and also found the trunk line had a leak in it. Apparently the line was routed poorly and was rubbing somewhere every time the trunk opened and closed. They cut out the holed bit of line, rejoined it with a good seal, and his system is now working fine.

c. I’ve rejuvenated my pump by electrically disconnecting then reconnecting it, and I’ve confirmed that there are no major leaks. Now what?

It’s time to evaluate your pump’s pre-set shut-off pressure. You can use any door or the trunk. Partially close the door/trunk and carefully watch the closing action. You’ll hear an audible click when the latch catches, but then the door/trunk will be pulled shut for a period of time after the click of the latch. Finally, the pump will turn off and the door/trunk will relax to its normal fully closed position. First, time how long it takes for the door to audibly latch. This should be about 1-1.5 seconds. If it takes longer to latch the door, your pump is not providing enough pressure. Why? Leaks, or maybe a worn out pump head, or something else (??). If you can’t find a leak, then I probably can’t help you further.

Now, time how long the pump runs after the door or trunk has audibly latched (that is, how long it keeps the door “sucked� closed after it latches). I found my pump ran for almost 10 seconds after the latch had clicked, needing extra time to build up enough pressure to trip the automatic shut-off. This extra pumping time is unnecessary. If your pump takes more than 7-8 seconds to shut off, then you’re a candidate for adjusting the shut-off pressure.

The pump only needs to run as long as it takes to latch the door. The risk of your pump running for too long is that every once in a while, before it reaches its shut-off pressure, it instead reaches the time-out time and charges a time-out to that line. After one more of these, that line is dead. The pressure shut-off is a balancing act. You want to set the shut-off pressure high enough so that enough pressure is developed to latch the door or trunk, but you don't want it set too high so that the pump takes too long to reach the set pressure and times out.

d. Adjusting the shut-off pressure

Pull out the pump and disconnect all the lines. Label them before disconnection if they aren't already. Unscrew 6 screws on the top of the pump and pry off the cover.



Admire the dual manifold design with solenoid switching between pressure and vacuum for each door and trunk line. Kinda cool. The pressure shut-off diaphragm is visible in this pic.



OK, here's the business end. Notice the dual contact switch that is operated by the white piston from the pressure sensing diaphragm. That white piston has a screw in the end of it which can be adjusted to adjust the shut-off pressure. If you screw it out a bit, then the piston will have to move less to trip the switch, therefore the pump will shut off at a lower threshold pressure.



Just turn the screw to adjust it. I just used needle nosed pliers. Finally, here's my original vs. new setting.



Now, your pump will shut down automatically in a lot less time after closing the doors and trunk. You can play with the adjustment a bit so that the pump run time is to your liking. I’d say 3-4 seconds after the latch closes is all that is needed, and you could probably set it for less than that. My closing assist system has run with 100% reliability for almost a year now, after performing the shut-off pressure adjustment. The obvious fringe benefit of this adjustment is that the pump runs for a much shorter time each time it closes a door, so it should also extend the life of the pump’s motor.

e. A case of a bad pressure shut-off diaphragm

This finding convinced me that most closing-assist system failures that W140 owners experience may well be caused by either maladjustment or failure of the pressure shut-off mechanism.

A boarder (posix) posted that his pump had quit running. I responded insisting that he adjust his shut-off pressure. When he dug into his pump, he found that the problem was not that the shut-off pressure was set too high, but that the white piston of the shut-off switch mechanism wasn’t moving at all. So his pump was timing out every time it operated. The piston had cocked to one side and bound in the black case becoming stuck (see pics above). He went farther than I ever had and disassembled the diaphragm (the black housing that the white piston moves in) eventually finding the root cause of the sticking piston. It turned out that the rubber diaphragm that pushes the white piston had developed a tear. The tear was on one side of the diaphragm such that as the pump pressurized, the diaphragm would push one side of the piston only causing the piston to cock sideways in the black housing. Since the pump develops quite a bit of pressure, the piston would get wedged in place tightly once it got started crookedly and become permanently stuck. Posix was able to take apart the diaphragm assembly and use the tip of a latex glove finger to re-seal the diaphragm and make it air tight again. Very ingenious, indeed. He said everything was back to normal, and he had also adjusted his shut-off pressure appropriately in the process.

Here’s a pic from Posix’ post showing the 3 screws (green) and the 3 solder connections (cyan) that need to be removed to take the pressure shut-off diaphragm off the circuit board for disassembly.



V. Conclusion

This is everything I know at this time. Please, let me know if you have anything to add, and I’ll update this with more “case studies.� I hang out regularly as “Brett San Diego� on the W140 section of www.mbnz.org.

Brett
 

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1997 S500
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281 Posts
The Messy Truth about Accumulators

First a quick history lesson on the MB hydraulic suspension.

Accumulators or Spheres as there sometimes called are the "springs" of most of the 140's rear suspension. The ride leveling system was installed on all 500's and 600's, optional on 420's and not installed in 300/320's - at least in the States. I've heard second hand that it was optional on 500's for most other markets. There are two different systems installed on these cars. The basic is a rear ride height control only and this system has no center console control switch- the system is transparent to the driver. This system has two accumulators. The other system has three accumulators and can be identified by a small switch on the enter console with a pictogram of a shock absorber. This system is called ADS or ADSII (Adaptive Damping System) depending on the model year. Basically this allows you to firm the suspension on all four corners. This system also controls the oil flow in and out of the front shock as well. This article deals with the two accumulator system because that's what I own- a 1997 S500 with ride height control. If you have ADS, the procedure is substantially the same- your just replacing three accumulators.

After about 80,000 miles the ride in these cars starts to deteriorate. Bumps that once went unnoticed now start to jar your hind teeth. When you notice that your starting to avoid manhole covers- it's time. What happens is the Nitrogen pre-charge starts to leak out. In a new accumulator, the pre-charge is set to 155bar- that's 2279psi! When the car hits a bump- hyd fluid is forced out of the shock and into the accumulator via a hydraulic line. This compresses the nitrogen gas inside the sphere- as the suspension expands on the back side of the bump the pressure inside the accumulator forces the fluid back into the shock. As the accumulator ages, the pre-charge leaks out and the void is filled with incompressible hydraulic fluid. This is where the ride stiffens up. When all the pre-charge is gone you basically have a hydraulic lock and the suspension stops working. My mechanic says he's seen cars come in where you can't compress the rear suspension even by jumping on it. It would be funny except that if you let your suspension go that far you risk damaging the hydraulic shocks- there about $870.00 a piece to replace. The accumulators are about $100.00 a piece to replace. You do the math.

In the two accumulator system, they're located approximately under the rear seat- tucked up and bolted to the underside of the floorpan. The driver's side (left-hand drive) accumulator is obscured by the exhaust system - not a problem. On cars equipped with xenon headlights, the right accumulator is blocked by the headlight level control. Simply unplug the electrical connector and remove the controller. Here's a few drawings from ALLDATADIY.com located at the bottom of the text.



On to the messy part!


Regarding the accumulators, the job is pretty easy, if not messy. Jack up the rear. If you don't have two floor jacks, try this- chalk the front tires and use the supplied tire changing jack to lift the car. Place a jack stand under the lift point (rubber doughnut) and set car on the stand. Move to the other side and repeat. Not ideal but it works. Please be careful! You might want to even "chalk" the car jack as it contacts the ground at an angle and on a slippery garage floor- well, it could slip. Bleed off as much pressure as you can using the nipple on the level control valve. I stuck some clear plastic tubing on to the nipple and cracked it open to let the hyd fluid and foam escape (brown foam means your accumulators are indeed bad). Once this is done you can remove the doughnuts or hangers that attach the exhaust system to the under side of the car. I think there were two on either side of the muffler and one just aft of the cats. I just unbolted them from the floor pan. This allows the system to hang down just enough to remove the driver's side accumulator. To remove the accumulator, simply remove the two hyd lines that attach to the accumulator and then remove the three mounting bolts. Prepare for an unholy mess at this point. Despite all my best efforts and warnings from other people I still dropped about a quart and a half of oil on the garage floor. Both sides require some finagling to get the accumulators out of their hiding spots but they will come. Some people have had trouble removing the hyd lines from the accumulators. This seems to be more of a problem for cars located in areas that use road salt. A good flare nut wrench is what is required here. This wrench looks like a standard box end except it has a small gap at the end that will allow you to slide the wrench over the hydraulic line. This wrench will help prevent damage to the soft metal nuts that hold the hydraulic lines to the accumulators. It should be noted that I was able to remove the lines with a standard wrench with no problems. Also be very careful not to cross thread the nuts onto the new accumulators. The hydraulic lines are stiff and if you don't line them up perfectly, you can cross thread the nut. This proved to be the most difficult part of the task. I had one on the right that would absolutely refuse to thread correctly. Patients, a beer, and another whack at it did the job.

Once both accumulators have been replaced I followed ALLDATADIY.com's instructions for filling and bleeding the system. Here's a reprint:

FILLING:

Pour oil into the oil reservoir

Only reuse clean oil

Set level controller lever to "Fill" position (F)
(loosen the ride height linkage- this will allow you to move the lever between FILL and EMPTY)
CAUTION
Risk of accident due to the vehicle starting off automatically when engine is running
CAUTION
Risk of injury due to bruising or burns when intervening while starting the engine or when the engine is running

Start engine, allow to run at moderate speed for approx. 60 seconds

The system bleeds itself automatically

Switch off engine

CAUTION
Ensure that there is sufficient oil in the oil reservoir
The pump must not suck in air under any circumstances

Set level controller lever (arrow) to position "Empty (L)"
After approx. 60 seconds, attach connecting rod or connecting linkage (7) to level control lever (arrows) NOTE:

Replace self-locking bolts and nuts
Place vehicle on its wheels and press down firmly several times.
The vehicle level adjusts itself
Check and correct oil level in oil reservoir

Be careful not to over fill the reservoir. I got a little too concerned about running the pump dry that I overfilled the system. Remember that when you move the lever to FILL, your filling the accumulators and raising the suspension. This will lower the reservoir. When I saw the low level ( lever still on FILL) I topped it off. Oops! When I moved the lever to EMPTY (engine off) The accumulators purged their oil and it flowed back into the reservoir. I heard this strange squirting sound. There was oil all over my garage wall. It had squirted out the overflow which thankfully had been pointing toward the front of the car and not into the engine compartment. Nothing bad happens if you overfill the reservoir- it's just messy and embarrassing.
Good luck!
Paul
 

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1995 S600 (sold)
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RE: The Messy Truth about Accumulators

pchansen1, this description needs correction...

The other system has three accumulators and can be identified by a small switch on the enter console with a pictogram of a shock absorber. This system is called ADS or ADSII (Adaptive Damping System) depending on the model year.

I have the ADSII system in my 95 S600. There are only two pressure spheres in the car. I have the "Shock" switch on my dash. If a vehicle is equipped with a third pressure sphere, it is used for the ASD system (not to be confused with ADS). This is the automatic locking differential.
 

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1997 S500
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RE: Knowlege base

I stand corrected- Thanks for the heads up, pcmaher.
Paul
 

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SEC 600 V12 2dr COUPE (RHD) One of the chosen few.
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2,233 Posts
Discussion Starter #32
RE: 38 PIN DIAG PLUG

OK well the kit I bought from germany arrived..And I am NOT impressed..seems I paid $184 for a tachopro ser2 setup.. without the software.. huh.. still not tried it yet.. HOWEVER..I will switch to plan B and consider this as the alternative.. I have found a fully functional 38 pin plug it was on a service light reset tool.. quite cheap.. will now try to get a A-D -usb converter..and write a simple interface..Pics of plug enclosed..





If you've GOT to have a extension,
Have a BIG one.

Torque isn't cheap
 

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Addendum: Newer pump pic and fixing leaky nozzles

f. The newer pumps with a different shut-off mechanism design and a technique for fixing leaks from damaged nozzles.

Another boarder (jvallet) posted that his S500 coupe was having driver’s door problems once again after pump replacement for the same problem 3 years ago. Jvallet found the door would work for a very short period, then stop permanently until he disconnected his battery. Then it would work again for a short time. Disconnecting the battery was serving the same purpose as removing the connector from the pump. When he pulled out his newer style pump and listened while it operated the driver’s door, there was an obvious hissing sound from a leak. He wiggled the air line connector on the output nozzle and found the noise changed. He found he could adjust the connector and minimize the leak enough to get the door to close, but the pump would run for 7-8 seconds before it reached the shut-off pressure. Although the leak was reduced, it was still audible. When he removed the air line, he found that the nozzle had a small chip broken out of it that appeared to be causing the leak. Jvallet wrapped the nozzle in what he described as water pipe sealant (I think Teflon tape) and then replaced the air line connector. When he tried the driver’s door again, it operated just fine, and the pump shut off automatically in about 2 seconds after the door latched. Problem solved. There were no more sounds of a leak.

Jvallet kindly provided this pic of the newer style pump. I have circled the output nozzles with chips in them. He reported the nozzles were particularly fragile, and he actually caused one of the chips when he was placing the cover back on the pump. On the right of the pump is the new design of the pressure shut-off mechanism. There is still a screw to adjust the shut-off pressure, but in this case, the screw is the actual electrical contact that turns the pump off.



Brett
 

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Fix for clicking/snapping door checks.

The door is a 97 S600 rear door. Here is what silenced my very loudly snapping door check.

Briefly, the door check is a cheap piece of stamped metal bent into a rectangle tube cross section, but one side of the rectangle is open. Because it's not a complete rectangular cross section of metal, two sides of the rectangle can be bent apart resulting in an overall trapezoid cross section. I think this allows the door check ball bearings, which are spring-loaded, to come slightly out of their groove then pop back in. I think the sound is caused by the ball bearing popping back in place, but I can't confirm that since the door check is not visible when mounted in the door so you can't closely watch its action when it's mounted. The fix was simply to put the check frame into a vise and bend it back to square. My rear door check is now completely silent except for the normal muted sound of the ball bearings hitting the detents in the check.

The story in pictures:

I took these pics after we had put the check in the vise once and bent it back a little already. It was worse before these pics were taken.



A close up showing the details.


The fix. We also put the check frame in the vise long-ways for a good squeeze all the way down its length.


Another angle at the door check.


The only problem is the check is pretty much guaranteed to click and snap again since it will bend again. Nothing you can do about it except maybe spot weld a small bar or two across the frame (in non-interfering locations) to keep the frame from spreading. Or, you can just buy a new one and start fresh.

After several months, my door check has started to click quietly again. (as I expected)

Brett
 
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RE: Knowlege base

My collection of DIY's I've done over the last few years. Mostly pictorial, and most for my 1998 S500. On the web page are about a dozen of the more than 100+ DIYs I've written for the model.

http://www.baxnet.net/merc/

Like yall were saying, it may be a good idea to do a DIY or an FAQ page.

Regards -

Greg
 

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W140 S 320 L & R129 500SL
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RE: Knowlege base

inetd - 7/23/2005 4:07 PM

My collection of DIY's I've done over the last few years. Mostly pictorial, and most for my 1998 S500. On the web page are about a dozen of the more than 100+ DIYs I've written for the model.

http://www.baxnet.net/merc/

Like yall were saying, it may be a good idea to do a DIY or an FAQ page.

Regards -

Greg
You mean make a new thread on DIY/FAQ page?Ok go for it here is it:

http://www.benzworld.org/forums/forums/thread-view.asp?tid=1220225&posts=4&fid=13
 
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RE: Knowlege base

Sure, you can link to it. Probably best as the content may change from time to time.

I think the DIY page is an excellent idea, or perhaps a forum with a series of stickies.

But you have my permission to do whatever -

Greg
 

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W140 S 320 L & R129 500SL
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RE: Knowlege base

inetd - 7/28/2005 8:42 PM

Sure, you can link to it. Probably best as the content may change from time to time.

I think the DIY page is an excellent idea, or perhaps a forum with a series of stickies.

But you have my permission to do whatever -

Greg
So what should we name the thread title?Any Ideas?

"W140 FAQ and DIY"
 

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My Thoughts

If I may voice my opinion,

You guys have a great idea going. But it's a little too much for me right now. The FAQs seem to be directed towards a newbie who has a basic mechanical understanding of the basic principles of a car, not a newbie who's looking for layman tutorials. But while I go out and seek that knowledge elsewhere, I do want you guys to know that it is really helpful ya'll are doing this. I'll definately be coming back here once I understand what ya'll are talking about. :)

Also, a quick question.

I understand this forum attracts Benz owners from around the world, so would these FAQs be universal? I live in the United States. Do American Benzes have the same designz as their European counterparts? Referring to Merc600sec's first FAQ on the A/C issue, I didn't know what he was talking about when he said to press the AUTO button, or to turn the tires to white?
 
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RE: Knowlege base

Sorry about that, I re-arranged my DNS. You can find the same S500 DIY site at: http://www.baxnet.com/merc

Notice it changed from baxnet.net, which I've decommissioned. So I just copied it over the new server. Hope this helps -

Greg
 
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