I'm fairly certain that 21 years is enough to make any rubber, almost anywhere in the car go bad.

Either that or 1986 wasn't a good year for rubber production in Germany.

I'm in the middle of a campaign to replace just about everything rubber on my early 300E. Injector seals, vacuum hoses, bushings, everything as I come upon it. My observations is that the iron bits on these cars will last forever. All of the annoyance comes from either rubber or electrical pieces.