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W140 Fix it Yourself Articles

468K views 267 replies 83 participants last post by  daone3256 
#1 · (Edited by Moderator)
Do you think we could have a database type thing so newbies can get acess to the things we all have to know about..we can get one for all those words and pics about silly things like bulbs and asr lights and window regs and...........we are repeating stuff constantly..And whilst I dont mind that.. would be nice to let others help themseves.. dont you think??????
RSVP
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MOVED THE MAINTENANCE THREAD INTO THIS ONE .
http://www.benzworld.org/forums/w140-s-class/1636494-maintenance-manuals.html
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MANUALS + LITERATURE + DIY SOURCES
Articles -thanks to Robert144
MBUSA old website -thanks to Thom_7
Buyer's Guide -by Merc-S600
Owners Manual PDF -thanks to Bayhas
Parts Manufacturer Country of Origin -thanks to Mercedes Mechanic
Zubehor-Accessories-Options Catalog
v12 uber alles cached link
VIN Decode Help -by MafiaDON
VIN Decoder
W140.de Photo Gallery
Maintenance Tips and DIYs -by Greg
Brabus W140 Catalog -by SL Brabus

HEATING & COOLING
AC Blower Regulator replacement -by MOS500 06/30/09
Cool Harness - Aux Fan Upgrade
DIY Coolant Service -by G-AMG
AC Vent Issue
AC Vent Issue 2 -by dr.charlesatlas
Replacing Evaporator and Removing the Dash -by Adrian126

ENGINE, TRANSMISSION & DRIVELINE
Where is the power steering reservoir?
Rear Engine Transmission Mount -by G-AMG
How to tell how worn out your 722.6 Transmission is -by MAVA
Fuel Filter -by Rainmaker
Complete Fuel System Cleaning -by G-AMG
Conductor Plate and Pressure Regulator Spring -by G-AMG
Steering Pump -by G-AMG
Rear Diff Oil Change -by G-AMG
Transmission Oil
Shifter Linkage Bushing -by G-AMG
Oxygen O² sensor - all 4 -by G-AMG

ELECTRICAL & WIRING
Antenna - see AUDIO below
Stereo - see AUDIO below
DIY Wiring Loom -by ScrapingScrap
DIY Rewiring ETA -from v12uberalles.com
Lumbar Bladder Replacement -by G-AMG
3rd brake lamp bulb replacement -by Stox & MOS500
3rd Brake Lamp LED Upgrade -by z168
Battery Service -by G-AMG
Center Lock Pump
Fuse Charts -by Bayhas
Dissecting the PSE pump -by MOS500
Side Mirror Repair -by MOS500
Warning Buzzer -not W140 specific and incomplete DIY, lifted from mercedesshop
1995 S600 Wiring Diagram -by Mercedes Mechanic
Gauge Cluster Bulb Replacement -by G-AMG

BRAKES, SUSPENSION & STEERING
Spring & Rear Bushing Replacement -by MOS500
Rear Spring Removal -by G-AMG
Power Steering Pump Overhaul -by G-AMG 11/10/09
DIY Brake Pedal groan/squeal -by MikeJT
Airbag & Steering Wheel Removal -by G-AMG
ASR Fixed! -by drcane
SLS Delete -by snik
DIY Rear Shock and SLS Delete -by MafiaDON

TROUBLESHOOTING & DIAGNOSTICS
Opening Trunk when Battery is Dead
Opening Trunk when Battery is Dead 2
P0455 Code -by Brett SanDiego
Hood Bonnet Not Opening

EXTERIOR & LIGHTING
Euro Fender Lamps / Side Markers -by z168
Headlight Removal -by G-AMG
Headlight Wipers
Headlights: US vs Euro
Modding How-to -by Hetzle
Wheel & Tire Fitment Thread
Trailer Hitch Install
Side Mirror Gasket Repair -by MAVA


AUDIO
Antenna Rebuild DIY -by innovation560
Antenna Rebuild DIY II -by nhzruthless818
Antenna Rebuild DIY III -lifted from K6JRF.com
DIY Aux Input -lifted from mercedesshop
DIY Aux Input 2 -lifted from mercedesshop
Becker Aux Input -by z168
Becker Aux Input 2 -by bobs
Becker Aux Input - late model
iPod/Aux Integration with Stock Becker Stereo -by LWB250
Integrating Aftermarket Stereo to BOSE Amp (for preface models 91-93) -by Merc-S600
Some Stereo Help
Generic DIY bluetooth integration (1) (2) - not MB content

INTERIOR
Center Console & Shifter Wood Removal - thanks to Rainmaker for the info
Cluster Removal -by bobs
Coolbox Fridge Option & Fuel Tank Info -by berlin420
Door Strap Replacement -by G-AMG
Euro Fire Extinguisher -by z168
Euro Trunk Warning Triangle -by z168
Interior Wood Trim Reference -by dbs600 & syljua
Rear 2-seat Conversion
Airbag differences (Early v Late model)

THOUGHTS ON W140 OWNERSHIP
Reality Check -by nimrodthewombat
Thoughts on ownership - W140 v LS400 -by SaleenS7
Enthusiast Perspective -by Stryker-1999 S600
More
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#27 ·
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
 
#28 ·
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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#29 ·
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.
 
#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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#33 ·
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
 
#34 ·
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
 
G
#35 ·
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
 
#36 ·
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
 
G
#37 ·
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
 
#38 ·
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"
 
#39 ·
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?
 
G
#40 ·
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
 
#41 ·
RE: Knowlege base

Hmm.. not been keeping an eye on this.. but I think it seems to be drifting away from the reason i set it in motion..

Though it would be good for those of us who can show those of us who might want to..

The info was to be posted here.. for us all to use..without recourse to other website info..

still ***
 
#43 ·
1997 S600 front main seal replacement

1997 S600 Front main seal replacement

This write up describes front main seal replacement on a 1997 S600 sedan. I have no experience with other model years. Things may be different on your car. This is not necessarily a difficult job, but it is a little technically involved and a lot time consuming, especially if you’re like me and you’ve never done it before. The job is made much easier with the right tools and a lift. I have a low-rise lift in my garage, and it got a work-out during this repair as there are a couple of things to do from underneath. DO NOT WORK UNDER YOUR CAR WITHOUT PROPER SUPPORT. BARE MINIMUM, USE SUITABLY RATED JACK STANDS OR RAMPS.

Special tools for the job that you may not have in your tool box:

Mercedes tool #602 589 00 40 00: This is a tool that holds the ring gear to keep the engine from turning while you loosen and tighten the bolt holding the crankshaft pulley to the crankshaft. My dealership quoted me $334 for it. Don’t even think about buying it. You can get away without it.

Mercedes tool #119 589 01 14 00: This is the seal insertion tool. My dealership quoted me $140. I did not buy it opting instead for the shade tree mechanic’s method of tapping the seal in with various tools. I describe my method below.

27mm 3/4in drive deep well socket (1 1/16in is the same size)
3/4in drive breaker bar (with a pipe cheater)
3/4in drive torque wrench . You need 300 ft-lbs (400 NM). This is a big wrench.

1. Remove the fan shroud and fan. Follow Pete’s directions here: http://www.v12uberalles.com/fan_clutch.htm. Because I was also planning to do a coolant flush, I gave myself more room by draining the radiator and removing it. The extra room is not necessary if you’ve got the MB tool for main seal insertion. I didn’t want to buy it. I used a rubber mallet and hammer to insert the seal so I pretty much needed the extra clearance that removing the radiator provided in order to work the mallet and hammer. It’s easy to remove the radiator once you have the fan shroud and fan out. Drain the radiator by opening the stopcock on the lower left of the radiator. Disconnect the transmission cooler lines on the right side of the radiator. These are the hard-line banjo fittings. Place a drain pan underneath and unbolt them. About 100 mL of transmission fluid will spill out and make a mess. I don’t see that this can be avoided, but it is a good idea to remember to replace the lost fluid when the job is done. Disconnect all coolant hoses, remove two nuts and bolts that hold the radiator to the AC condenser, and simply lift the radiator out of the car I plugged all openings in the radiator to prevent dust and dirt from entering.

2. Remove the belt and clean the engine. Take a picture or draw one of the proper belt path. Slacken the tensioner with a 15 mm wrench on the bolt in the middle of the pulley, and remove the belt. The pics below are before and after cleaning pics. I used Gunk Engine Brite. It had been leaking slowly for a while, but the Gunk worked wonders. I was impressed. I’ve also removed the tensioner pulley (one bolt in the center of it) and power steering/hydraulic suspension pump pulley (3 bolts in the face of it) as noted in the pic. This gives more room and a better view of the crankshaft pulley.




3. Rotate the engine to top-dead-center (or close to it). To do this, put a 27 mm socket on the crankshaft pulley and rotate the engine clockwise when you’re facing the engine from the front until you see the 0T mark on the crankshaft pulley. Line this mark up with the point cast into the engine block as shown in the pic (or just get it close). Actually, this could be TDC or 180 degrees past TDC, but it’s not important for this job. The reason for doing this is to ensure that the Woodruff key that links the crankshaft pulley to the crankshaft is on top of the crankshaft. Otherwise, the key may fall off the crankshaft and inside the engine into the oil pan. See below for pics of the key. If the key falls into the oil pan, you have no choice but to remove the oil pan to retrieve it. When I removed my pulley, I found the Woodruff key was stuck to the crankshaft. I couldn’t remove it with mild pressure from a right angle pick, so I just left it in place and figured I had nothing to worry about losing it. WARNING: Do not rotate the engine counterclockwise. Always turn in the normal running direction of the engine.



4. Prevent the engine from turning counterclockwise while you loosen the crankshaft pulley bolt. The factory tool mentioned above prevents the ring gear from turning. We’ll do the same thing much more cheaply using a Mercedes mechanic‘s trick taught to me by my father-in-law. He owned a MB repair shop for a while in the past. First, remove the ring gear access hole cover on the transmission shown in the pic. Wedge something in between the ring gear and the transmission housing so that the ring gear won’t turn counterclockwise (as you’re looking at the engine from the front of the car). I used a 3in long piece of 1/2in square solid steel bar. See pic for how the bar is put in place. NOTE IN THIS PIC THAT THE BAR IS PLACED TO PREVENT THE RING GEAR FROM TURNING CLOCKWISE. FOR THIS STEP, THE BAR SHOULD BE ON THE OTHER SIDE OF THE RING GEAR.




5. Remove the crankshaft pulley bolt. This is where you need a big wrench. The factory torque spec on the crankshaft pulley bolt is 300 ft-lbs. Hopefully, the steel bar placed to stop the ring gear holds. When the bolt is out, keep the four washers on the bolt as they are. They are concave and should stay in that orientation with the concave side facing the engine. The bolt should be a little damp with oil. It is oiled when it is installed because of the high torque it receives. When I was replacing the pulley and torquing down the pulley bolt to 300 ft-lbs, the bar didn’t hold the ring gear as placed in the above pic. It got gouged by the ring gear teeth and slipped out. I had to resort to a long bar inserted through the torque converter bolt access hole and through the ring gear. In this position, it catches a spoke of the ring gear and stops it from turning. This is clear in the pics below in the steps on reinstalling the pulley.

6. Remove crankshaft pulley. Be careful not to damage the rubber outer circumference too much. I used a pickle fork and hammer from underneath, alternately driving the fork between the pulley and engine on either side of the shaft until the pulley began to come off. I then worked the pulley off the crankshaft by hand from the top. You may be able to work a crow bar from the bottom, too. Be careful of the Woodruff key as you remove the pulley. Don’t knock the key into the engine. Like I said, my key was stuck to the crankshaft so I didn’t have to worry about it. If your key is loose, carefully remove it.





7. Clean around the main seal, and remove the old seal. Plug the opening with something (I used lint free wipes.), and use a wire brush to clean around the old main seal. You don’t want junk entering the engine. Cover a screwdriver with a towel and pry out the old seal.




8. Inspect crankshaft pulley for wear. There will be a polished ring where the old seal contacted the pulley. This is normal. If there is an obvious groove or other wear marks, that is not good. Take a close look. Normally, the seal is installed flush with the engine (see pics above), but Alldata and the MB W140 CD both say to install the seal 3 mm inboard of flush with the engine if there is wear on the pulley. This puts the contact area of the seal on the crankshaft pulley 3 mm inboard of the old patch. This part of the pulley will be clean and fresh since it has been inside the engine the whole time. The factory seal installation tool is designed to handle either installation by simply using the other side of the tool to insert the seal. I guess you get two chances to use your crankshaft pulley, then you have to buy a new one. My pulley had an odd rough spot, about 1 mm X 2 mm right in the polished contact patch, so I opted to do the recessed “repair� installation.



9. Install new seal. While hunting around the local hardware store, I found some big nylon washers that happened to be exactly 3 mm thick and about the size of the main seal. I bought one and trimmed it down in diameter so it was just smaller than the seal. See pic. This will be the final depth-setting insertion tool.



My father-in-law then gave me a piece of PVC piping that was almost the exact diameter of the seal, too. I used this to start the seal and get it flush with the engine. You just need something cylindrical and sturdy and about the same size as the seal. As the pic shows, put the seal in place by hand, place your “insertion tool� flush with the seal, and use a mallet or hammer to tap the seal into the engine. Work your way around slowly a couple of taps at a time, trying to keep the seal fairly even all the way around. Note: I taped a large piece of cardboard to the AC condenser to protect it. The condenser is exposed when you remove the radiator, and I didn’t want to risk damage to it. Work until the seal is flush with the engine. If you’re doing a normal install, you’re done. If you’re installing the seal 3mm recessed, time to get out your 3mm thick final insertion tool.



I put my nylon washer over the seal and slowly tapped it with a hammer, working around its circumference. Once the seal was recessed partially, I took a short piece of 1/2in square steel bar, placed it across the seal and washer, bridging the seal opening as shown in the pic, and tapped the bar to finish seal installation. Again, I worked the bar slowly around the seal trying to keep it going in straight, tapping twice at each stop. I tapped until the bar contacted the face of the engine all the way around the circumference of the seal. This should ensure a uniform 3mm depth all the way around.




10. Install crankshaft pulley. First, oil the inner lip of the seal. I used a Q-tip dipped in clean motor oil. Install the Woodruff key onto the crankshaft. (Mine never came off, which made life easier). Align the notch in the crankshaft pulley with the Woodruff key, and manually slide the pulley on the crankshaft until it hits the seal. Don’t force it in. You’ll use the pulley bolt to finish sliding the pulley through the seal and onto the crankshaft. Again, do not knock the Woodruff key into the engine!



You should oil the pulley bolt again with a little motor oil. Not a lot, just a little.



Start the bolt by hand until it stops against the pulley. Use your 27mm socket and breaker bar (or large ratchet) and start turning the bolt to push the pulley onto the crankshaft, until the pulley is all the way on. For final torquing, you will again have to block the ring gear in some way. As I said above, the square bar wedged between the ring gear and transmission housing didn’t work this time. The bar kept slipping out. So I found that I could insert a longer bar through the torque converter bolt access hole and all the way through the ring gear as in the pic below. (The Q-tip is there just as a soft wedge to hold the bar in place as I turned the engine from the pulley bolt until the spoke in the ring gear caught on the bar. I didn‘t have a buddy helping out who could hold the bar in place.)



11. Final torquing. This should be done in a couple of stages. Put the big torque wrench on the pulley bolt and torque to 200 ft-lbs. Wait 30 min, and then torque to 300 ft-lbs.



12. That’s it. Reinstall everything as you took it off. I hope you took good notes and pictures to help you get it all back together. If you removed the radiator, don’t forget to replace the lost transmission fluid. You just add it through the dipstick.

I’ll have to wait and see if my first main seal replacement was a success. Hopefully there will be no more leaking from the new seal. If it leaks, I will probably buy a new crankshaft pulley. I didn’t want to do this because it costs either $700 or $900 from the dealership (depending on my VIN). I didn’t go back and give my VIN to get a final price. I will also probably buy the factory seal insertion tool just to make sure the seal gets in place nice and straight. My father-in-law said I didn’t need it, but he’s an experienced mechanic and knows what he’s doing.

Brett
 
#45 ·
Addendum: Severe leaking from the pump head.

g. Severe air leaks from loose bolts at the pump head.

A poster (SEXYREX) recently related his experiences with fixing a major leak inside his pump. Every time he reset the pump by pulling the fuse, he would get two operations then nothing from each line. Even firmly blocking an output line with a finger, did not cause the build up of enough pressure to trip the shut-off switch. Clearly, there was a major leak central to the pump since every line was affected equally, or there was a problem with the pressure shut-off switch causing timing out. After some inspection, he noticed dust patterns indicating air escaping from the seam in the pump head. It turned out that the screws holding the pump head together were loose. A quick tightening of the screws completely restored function. Now, when firmly blocking an outlet nozzle, the pressure shut-off switch turns the pump off immediately as it should. After adjusting the shut-off pressure, all doors operate normally, and the pump turns off about 3 seconds after latching.
 
#46 ·
RE: Knowlege base

Thx for that Brett,
I just came from my MB mechanic and asked him to do that for me and he said he would like a picture of the pump, cause he does not understand exactly what I mean.

I do not know if it is possible to highlight the part of the pump that needs tightening. He says accessing it isnt difficult.I am also posting something about the brakes that he did today in an appropriate forum.
Thx again
PGP
 
#49 ·
1997 S600 water pump and thermostat replacement

1997 S600 water pump and thermostat replacement

My water pump locked up on me while driving home a couple weeks ago. Fortunately, I was less than a mile from home and could make it the rest of the way before overheating set in. I was particularly bummed since I had just had the radiator out to replace the front main seal a couple months ago. Now, it’s all going to have to come apart again. At least this time, it took only 45 min. or so to remove the radiator to get started on the water pump. I was informed that one could do the pump replacement w/o removing the radiator, but I decided I wanted to have the extra room to work, so I removed it. I decided also to replace the thermostat and to replace all the O-ring seals (5) associated with coolant circulation at the front of the engine. My car is a 1997 model S600 sedan. Other model years may be different.

My pump’s failure mode. Here are pics of the locked up pump. It turns out the outer bearing had rusted out allowing the shaft to wobble off center. When this happened, the impeller contacted the pump housing internally causing the pump to lock. The inner seals were OK so no coolant ever leaked out. My car spent its earlier life in New Hampshire. After several New England winters and 115,000 miles, I guess it is about time for this to happen. I assume the water pump is original to the car.



1. Drain the coolant. If you’re going to reuse it, drain into clean containers. Put a tube (12 mm ID, I think) on the stopcock outlet at the bottom left of the radiator. The small pop out panel in the bumper on the left side allows easy operation of the stopcock with a screwdriver without having to crawl underneath. Pop out the panel and open the stopcock to drain the radiator and reservoir. Have enough containers ready. About 2.5 gallons of coolant will drain out.

2. Remove the fan and fan clutch and then remove the radiator and hoses. Follow Pete’s directions here to remove the fan clutch: http://v12uberalles.com/fan_clutch.htm . Removing the radiator now involves just disconnecting all hose connections to the radiator (water hoses and transmission cooler lines) and lifting the radiator out of the car. When disconnecting the transmission cooler line banjo fittings on the right side of the radiator, a small amount of transmission fluid will spill out and make a mess. You can’t avoid this as far as I can tell. You’ll also have to move the intake cone for the left-side air box out of the way of a plastic tab on the radiator in order to lift the radiator out. Either pull the cone forward or just take the air box out of the car.

3. Protect the AC condenser from damage. Cut a piece of cardboard big enough to cover the AC condenser and tape it in place. You don’t want to have to buy a new condenser. I dodged a bullet this time. I initially forgot to protect the condenser, and as I was removing the stuck fan pulley, the pulley released suddenly and struck the condenser causing a significant dent but no leak fortunately.

4. If the poly-rib belt is still in place, loosen the bolts of the fan pulley and the water pump pulley with the belt holding the pulleys. Then remove the belt and the pulleys. To remove the belt, put a 15 mm socket with a breaker bar on the bolt in the center of the tensioner pulley, turn the tensioner clockwise to release tension, and work the belt off. The pulley mounting shafts are probably rusted making pulley removal a bit difficult. My pulleys released from the backings OK, but sliding them off was difficult. A little WD-40 worked well.

If your belt is no longer in place, use a screwdriver wedged between the bolt heads and the fan pulley flange or the pulley shaft to hold the pulley while you loosen bolts as shown in the pic below. Note that this pic was taken on reassembly, which explains why everything is so clean. The bolts should be torqued to only 10 Nm.



5. Remove the small guide pulley at the top right of the engine. Pop the small cover off the front of the pulley, and use a 6 mm allen on the bolt in the center of it.

6. If you’re going to remove all the coolant pipes to renew the O-rings and thermostat, you’ll need to remove the plastic shrouds that protect some electrical bits at the top left and right of the engine. Each one has three 5 mm allen head bolts holding it in place. The one on the left cylinder head is a particular pain. It requires disconnecting some vacuum lines and electrical connectors from switches associated with the air injection system. Then you have to battle the power steering reservoir hoses on the lower end of it. It will come out, but it isn’t easy. I ended up breaking the shroud at its thinnest point as I pushed it back into place.



7. Remove the thermostat and the coolant pipes from the cylinder heads. Start by removing the 4 bolts (5 mm allen) holding the thermostat housing. I thought it would be a piece of cake to remove the thermostat at this point, but the built-in engine lifting eye blocks removal as seen in the pic below. And, the thermostat blocks removal of the bolts holding the eye in place from what I could tell. I ended up removing the thermostat housing and the coolant pipes from the cylinder heads as one unit. Remove the 4 bolts (2 on each side, 6 mm allen) holding the coolant pipes to the cylinder heads. Pry the coolant pipes from the cylinder heads. There was a lot of corrosion and crud built up in the joints so it was difficult to remove the pipes.





8. Clean all the joints and mating surfaces where O-rings seal the pipes. This pic is of the thermostat housing seal. All of the joints looked like this.



I used a wire wheel bit on a Dremel tool on all the O-ring seats. It took a little over an hour. This is where doing your own work becomes satisfying. No mechanic who wants to be profitable would take all the time necessary to really clean things up good. Here are the results. Some pitting from corrosion has occurred, but mostly it’s external to where the O-rings seal the joints.



I’m a little concerned about some larger pits on the underside of the thermostat housing, where it meets the water pump. Hopefully, the O-ring will seal it OK.



9. Remove the water pump. Remove the 10 bolts (nine 13 mm and one 6 mm allen) holding the water pump to the engine.



10. Scrape away the old gasket and clean the surface. I used the Dremel wire wheel again. Here’s the old gasket.



And, here’s the cleaned up surface.



11. Fit the new water pump with a new gasket. Directions on www.alldatadiy.com specifically say not to use any gasket sealant. It’s difficult, however, to get the new dry gasket to stay in place as you fit the pump. What I did was dab a very small amount of silicone gasket sealant on the very outer edge of the bolt hole “ears� on the gasket then placed the gasket on the engine block. That was enough to stick it in place. Torque bolts to 21 Nm (not very much at all, but it’s enough).

12. Fit all the new O-rings, install the new thermostat, and reinstall the thermostat housing and coolant pipes on the cylinder heads. I wet the new O-rings with distilled water as a lubricant to help with installation. I had to knock the thermostat housing slightly with a hammer to get the thermostat bolt holes to line up with the water pump again. The power steering pump reservoir hoses have to get squished a little for the thermostat housing to line up correctly.

13. Reinstall the pulleys. Torque bolts to 10 Nm. I had one issue reinstalling my water pump pulley. The water pump has a drain or vent pipe exiting just behind the pump pulley. I suppose this allows the air in the cavity between the inner and outer shaft bearings to escape as the engine heats up in order to prevent the seals from being pushed out of place from gas pressure. It also could be a coolant drain in the event of failure of the inner seal.



Well, this tube comes pretty close to the back side of the pulley, which has a strange lip all the way around it. My guess is that the tube sort of fits inside this lip, which helps to prevent water, salt, and any other debris from entering the cavity and corroding the pump bearings from the inside out.



The pump I bought is made by a German company called LASO. Apparently it’s not OEM since the pulley came into contact with this tube and couldn’t be installed. I used my trusty Dremel with a cut-off wheel to hack the drain pipe a bit to make clearance for the pulley.



14. Reinstall everything else in reverse order of removal. The small guide pulley gets 30 Nm.

15. Refill with coolant (50/50 mix of distilled water and MB factory coolant). Start and run until warm with the heater running to fully circulate the coolant and clear out air bubbles. Top off the coolant as necessary, and check for leaks.

16. It’s probably a good idea to replenish the lost transmission fluid. Not much comes comes out, but it’s worth making sure the transmission is filled properly. Unfortunately, you have to break the red plastic clip on the dipstick tube cover to be able to add fluid, and you have to buy a dipstick to measure the fluid level properly at 80 degrees C fluid temp. Thank you, Mercedes-Benz, for making simple maintenance difficult.

Brett
 
#50 ·
Addendum: A case of a plugged pressure shut-off mechanism in the new style pump

h. A case of a plugged line to the pressure shut-off switch diaphragm in the newer style pump.

A boarder (GotBenz) posted that he was experiencing the typical loss of function of the doors and trunk one at a time in rapid succession. The fact that all the lines were affected is indicative of a problem central to the pump rather than a leak in a single line. He found he had the new style pump in his W140. When he tried to turn the copper screw of the shut-off switch mechanism, it seemed really stiff and resisted adjustment. (I only know this pump from a picture. I’ve assumed that the screw is a pressure shut-off adjustment, but if it is fixed, then the shut-off pressure may not be adjustable. I’ll update my info when I learn more about the shut-off mechanism of the new style pump.) GotBenz then attempted to adjust the shut-off pressure by shortening the distance between the switch contacts by dabbing solder on the moving copper arm of the switch. It didn’t work reliably. I suggested that he take a close look at the shut-off mechanism while in operation, and he found that the copper arm of the shut-off switch was barely moving. Further investigation revealed the culprit. The pump head is made of a black material that produces a fine powder as it wears. It may be graphite or just a plastic. This powder had plugged the line going to the pressure shut-off diaphragm, so the switch wasn’t operating properly. GotBenz simply removed the plugged plastic part and blew backwards through the line ejecting the powder. Upon reassembly, the shut-off switch was back to normal operation, and pump operation was completely restored. In his own words, “so.. with a swift blow through one of the air inputs, a large, rather hideous cloud of "black smoke" came spewing out the other nozzle. Be careful and point the air nozzle away from face when doing this.. or suffer the consequences like i did.. haha.. anyways, reassemble air hose, and problem fixed!� The pic below points out the part where the blockage had occurred.

 
G
#51 ·
RE: Knowlege base

Great post on the water pump. IMHO this is something that needs to come off as preventative maint. My best guess is 100K miles, I did mine around 70k.

Your level of notable work is outstanding. No, not many would have cleaned up the metal, and if left unchecked could have eventually corroded into the block, and very well demanded a replacement before 250k miles.

But a little foresight and attention as you have given will keep a motor (even a 120) running for 1/2 mil plus.

It's just a shame some say (I'm now speaking in my most ******* voice) "Well sheet, I never done nothin like clean a pump housing like that in 10 years ain't gonna start now - Hey Vern! Gimme another Buttweiser..." lol

More power to you Brett - it's all in the attitude
 
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