Definately, take that car to a mechanic before you purchase it if you want it that bad. I avoided getting a 1987 300SDL that had problems on it that the mechanic discovered before we were supposed to buy it. The guy who was selling kept on saying, it's in great condition, great car, but when the engine and tranny are about to go out, not so great. So, go get that car checked out, and if the owner won't let you, just forget it, there are other 83-85 Turbo Diesels out there.
-Joe

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.