I just purchased 1988 560 sel with 136,000 miles, the nitrogen cells were replaced 2 years and 20,000 miles ago. It rides over little bumps like there is 150 lbs air in the tires. I want the car to have a soft smooth ride and not into performance handling, any suggestion, is this normal, how do I make it ride smooth. Thanks

It still sounds like accumulator problems. If you are feeling the harsh hide thats the answer. If you are hearing it instead, I would look to the upper strut bushings in the rear. During the time the cells were bad they took a terrible beating.

I would suggest to bring it by cause I could tell you in a five minute road test, but there are others much closer I assume. An experienced MB tech will know the condition. The other alternative is to test. If you are paying for it the test will cost as much as one (or more) of the accumulators.