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)