Thump in rear of 124 4matic - NOT speed related

Good day to all,

I've been away for a while, but keeping an eye on the list. I have a real challenge for any serious mechanics with 4-matic experience. After changing the rear suspension accumulators on my '91 300TE 4-matic, I now have a thump coming from what sounds like under the right rear passenger seat, which is about where the 4-matic computer lives, IIRC.

The thump will occur every 5 - 10 seconds, and will continue whether the car is in motion or stopped, in gear or in Park, and regardless of engine rpm. I am thus able to say it is not drivetrain related, but sounds more like a solenoid activating. This noise will sometimes go away after driving for a while, but then reappears later.

I'm at a loss, and I'm worried that if it's a solenoid in the 4-matic computer, I'm going to wear it out through over-cycling.

Help is obviously appreciated. Happy New Year to all!!

someguyfromMaryland