If you're getting fluid spit out of the abc reservoir , or a brief red abc warning flash in your dash when you go over bumps , you have one or more failed accumulators


Here's a nice article showing where they are in your car with lots of pics
http://www.edmunds.com/mercedes-benz...nd-repair.html

 

They are not that hard to replace if you have some mechanical know how. Mine started with brief warning dings over big dips in the road and then after the right rear blew the rear was very bouncy with almost constant warnings. I spent about $1500 replacing them, a seeping hose to the front right shock, and having both valve blocks rebuilt. That was about 30k miles ago. Knock on wood no issues since. It's time for another flush and filter though.