ABC Questions?

[kengriffith]

OK, ABC warning light on 2110 S500 with Active Body Control. Took it to two different Mechanics, got two slightly different answers. By the way, the car isn't lowered or listing in any fashion, seems to ride well, just the warning light.

1. One says I need a new ABC pump. If that is correct and the pump is a dual pump, why is the power steering still working fine? Also, can I install the pump if I buy it from Phil at fastlane?

2. Another says Air cells for ABC system. What are air cells doing in a hydraulic system?

Finally, a temperature sensor for the ABC system. Can I replace?

Anyone ever done some DIY on this system.

Finally, Finally, Strutmasters has replacement systems for airmatic systems. Can these ABC systems be replaced by standard shocks and struts?

KG

[kengriffith]

That would be a 2001 S500 with ABC

KG

[ILUVMILS]

A little more information would be helpful. Did either of the two mechanics check the system for fault codes? If not, be wary of letting them try to fix your car! For Mechanic A to recommend replacing the tandem pump without first checking for fault codes doesn't make any sense, unless of course the pump is leaking. Did he check the actual pressure? Mechanic B clearly doesn't know much about the ABC system (Air cells???).

Diagnosing the ABC system can be quite complicated, but in many cases it can be very simple. MB has issued several bulletins about how to deal with the different failure scenarios common to the system. Since you say you're not having any ride height issues, I think your problem can be solved quickly and inexpensively (relatively!).

The first thing you should do is have the system checked for fault codes. I'd bet that you'll find code "C1525-System Pressure Too Low", and/or "C1526-Malfunction in Pressure Supply". If so, a simple inspection for any leaks should be performed. Even a small leak can delay the pressure build-up after starting the engine, resulting in the warning message you're getting. If no leaks are found, the cause may be as simple as the system pressure sensor not responding quickly enough. The important thing to remember is that the ABC control unit looks for pressure build-up immediately after start-up. Any delay will trigger a warning message.

Of course, there are many more possibilities. The scenarios I've described are the most common, in my experience. If you get the warning message immediately after starting the engine, you should proceed as I've said. If the warning appears while driving, that's a whole different ballgame. Have the system checked for fault codes, and let us know what you find.

[kengriffith]

Three honest mechanics and really hard to diagnose. We have a fix however.

Once again the issues and symptoms.

1. The ABC light is coming on periodically saying there is an issue with the system.

2. The fault codes are saying there are system pressure problems and a system tempeture problem.

3. The ride is still OK, Nothing is leaning.

4. We do in fact have a bad front left stutt.

Took it to the dealer to get those codes. They say probably needs a new pump , but no gaurantees on the ABC system. Could need other things as well.

Another good independent is also saying probably a pump as well.

OK, what finally fixed this thing.

Independant took a stethascope to the pump. It was running really loud.
Wondered Why.

Did a rodeo and all the System components checked out OK. He determined that before we do anything, lets make sure the accumulators are OK and the fluid is OK. Reasoning that if we have to replace the pump, we are going to change out the fluid anyway. Well it turns out the middle accumulator was completely shot. The membrane had somewhat dissintgrated and no nitrogen left. and the fluid was full of the membrane crap, Because the center accumulator couldn't function, the pump was working overtime having issues keeping up the pressure, and the system was running hot, causing all the error codes.

The fix was new fluid and a new center accumulator.

It took quite a while and a real committment from the independent to not just start replacing parts(particularly the pump) and I don't think just anyone would have spent the time and effort to diagnose the problem like he did. He did it because I was telling him I didn't want to spend six or seven thousand dollars on a car that on edmunds was never going to be worth the kind of money it was taking to fix. He loves the W220 cars and hates to have people spend that kind of money either. It is now fixed for less than a grand and round of golf. (Doesn't count the cost of replacing the strutt, that baby still cost a small fortune)

[Hirnbeiss]

Would that be a Pebble Beach round of golf, or a Jersey Hacker municipal course walking?