Im a new member but have been following the forums for quite some time now ...I have an ABC situation that some of you may have some sort of insight to as I will probably have to do the majority of my ABC repairs myself if possible ... Here is the situation as follows.... 2002 CL500 125000 miles had it for about a year now with no problems at all....The ABC system was working fine up until 2 months ago when suddenly my front passenger strut would randomly raise to an extremely high position in idle or if i drove into a dip or over a bump too fast... did not get any kind of ABC warning when this happened but I would have to cut the car off then back on and the strut would come back to normal level..... a month later my ABC (white/blue then red) light came on while the strut was raising high and restarting it didnt solve the problem and the car then proceeded to sink to the ground... I checked the hydraulic fluid and it was black and smelled burnt (contaminated) and fluid had come back up through the resivoir(accumulator failure possibly) so I left it alone started the car the next day and it lifted up enough (front driver strut was locked in the same extremely high position as before when it lifted backup off the ground) for me to get it to the indy shop that I go to for repair and service of my vehicles (specializing in only mercedes but I dont think they are completely well versed on ABC systems as in they know about them but obviously in this situation not enough to fix this problem) and they ran the star diagnostic and found that the pump was dead and putting out no pressure so they ordered a NEW pump... and during the time I was waiting for the pump and getting it back to the shop (about a week) my rear driver side strut completely went down (no known leaks anywhere from the strut either.. i know they have travel sensor issues so that could be a possibility or stuck or dirty rear valve block issue) and the front passenger strut was locked and raised in an extremely high position.. so they put the new pump on and there is no response at all when the height level adjustment button is pressed and the car is still locked very high on the front passenger strut and sagging extremwly low on the rear driver strut and the red abc light came back on and stayed. so they tried to find out what was going on with STAR and found that the pump was putting out good pressure but that was it and also found a few codes but I didnt bother to get them in my moment of severe frustration ($1,350) since they told me they didnt know what else to do but go to the dealer for repair.. They even swapped an ABC control module (possible culprit) from another CL500 and still the same thing.... So now I am on my own with it and am going to let a dealer diagnose it and go from there... from what I read here I am leaning towards a valve block (both)/accumulator(rear)/pressure valve/pulsation damper (any or all) type malfunction but I was hoping that some of you might have some insight on this situation.. also I dont think the fluid was flushed when they replaced the pump nor did they do a ABC system bleed. ......on the paperwork it just says that they added 3 liters of new fluid..and I know how critically important flushing the fluid and or bleeding the system is during these repairs to get out contaminated fluid and or debris and im almost certain that my system is still contaminated with dirty fluid/debris being that the pre repair fluid was blackish brown... once I take it to the dealer and get the codes then I will have a better idea and be able to post them in order to get some assistance..... I DIY repaired/replaced the airmatic suspension (struts,valve block, pump)on my 02 S430 but ABC is a whole different ball game of its own that I am willing to work on and repair myself if possible and I need all the help I can get...I have been studying the forums so I can come up with a gameplan and get this thing rolling again. thanks in advanced and any insightht would be greatly appreciated.

 

When the car raises itself in one corner its a internally leaking valve block most of the time.

If the fluid smells burnt I would suggest you replace the oil and filter before you go any further. As the system cant be drained you'll need to use a flush method. The best option involves running the return line (off the oil tank cap) into a large container or bucket. You need a second person in the drivers seat to turn the car on/off for you. Fill the oil tank pretty high up and get second person to start the car. Get them to raise/lower the car whilst you are refilling the oil tank at the same time. If the oil tank gets under 1/4 full then turn the engine off immediately as you don't want the pump to be staved of oil. Normally I would do this with hot oil, if you have never done it before then do it when it's cold as it's much safer.

Once the oil going into the drain container is clean turn the engine off and reassemble the oil drain hose with a new filter.

Retest for the car dropping/raising for a week. Don't be alarmed if it becomes worse, it can do when there is new fluid in the system. If it still drops or raises then the valve block would be leaking internally. Replace the affected valve block and refill the system. If you replace a valve block then I suggest replacing the pressure accumulator (near the steering rack from memory) at the same time as a precaution and the oil filter again.

You must remember to be as clean as possible when working on a ABC system, the internal clearances are extremely tight and the smallest amount of dirt can cause damage.