Hmm... the only across the board issue I can think of is the wiring harness. The ones through about 1995 had bad insulation, and would often fail prematurely creating a huge variety of symptoms. Many of these were changed under warranty. I've seen some reports of leaking from the head gasket, but that was really more of an M103 problem. That's what I recall FWIW - 'course I don't have one, so maybe someone w/ personal experience will help.
82 300 SD
77 450 SL (gone)