97 S500 coupe with 152k. Thump from left rear when going over potholes manholes etc. Dealer Diag was air cells. 2 new air reservoirs and 500 bucks later still have thump. Are oem shocks long in the tooth at that mileage? Also, I had similar issuse with an XJS and it was bad bush on top of front strut. Not familar with W140 so do not know if same problem is possible cause.