Thanks to knowledge supplied over the years by members of this forum, I have a pretty good working understanding of my '91 560SEL's hydraulic rear suspension system. Unfortunately, my knowledge is insufficient to figure out an issue I'm presently experiencing with it.

Whenever I cut the engine, hydraulic oil begins gradually bleeding out of the struts and working its way back into the reservoir. After a few hours, the reservoir is nearly full and the car's rear is clearly sagging. The system is otherwise working normally: upon driving for awhile (or upon adding weight to the trunk and getting the RPMs up), the level control valve does its thing and the system is properly re-pressurized. The ride becomes progressively more comfortable as the rear end lifts, and--of course--the suspension fluid in the reservoir drops to the correct/normal level.

From the service manuals, I can't find a clearly described check valve--though I suppose the level control valve might serve as one, and be the source of this annoying issue. FYI: I last changed the accumulators not too long ago, and I flush and refill the system every year or so. There are no leaks.

Any help in diagnosing and dealing with this undesirable de-pressurizing behavior would really be appreciated.

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Eric

1991 560SEL-Euro (214,000 miles)
1989 420SEL (Retired from daily use at 325,000 miles; Use as donor vehicle)