I have a 1984 500SEL Euro and after I bought it I started reading some of the posts on this forum. The overall consensus seemed to be that the 84-85 500SEL's were not what they were cracked up to be. Everyone seemed to agree that they were nothing but money pits. After hearing about all these problems you are having, Benzman500, I'm starting to think that maybe they were right.
I have only had mine for about a year and I haven't had anywhere near the problems that you are having (knock on wood). Then again, I had a top notch MB mechanic (direct from Deutschland)give it the once over and fix up all of the little stuff before I got it in my hands.
Oh by the way -- Does your 500SEL Euro have the hydropneumatic suspension on all four corners as well?
84 500SEL EURO 87K
85 300D 267K (and still goin' strong)