How to know your ABC Regulator Accumulator has failed
 

On searching for possible sources of noise at idle to 2000 RPM, I've noticed that many people have bad noise that "disappears" at driving RPM. This noise is best described as a bad bearing, or a buzzing solenoid valve or water fill valve on a toilet that varies with motor speed.

After chasing down this noise for two weeks, I finally got down and felt the pressure regulator (behind right front wheel) and could feel it vibrating.

I replaced the ABC accumulator on it with P/N 2203270215 (which only took 5 minutes) and all noise and vibration went away. Upon inspection of the failed accumulator, there is no indication that this one fails the way the others do because you cannot insert anything into it. The car drives fine over bumps with it failed and there are no warning light ever, just the sound of the mechanical relief valve vibrating open and closed to maintain the hydraulic back pressure. Any component can fail, but before replacing the very expensive and difficult to damage mechanical relief/regulator valve, I would take the gamble of just swapping out the accumulator first.

thanks for sharing.:)

Keep in mind, the other 3 accumulators are also likely to be in the same condition.

Here is how to change the others:

http://fotifixes.com/2015/01/18/how-...rcedes-cl-215/