Correct me if I am wrong, but I think they are automatically adjusted on the 86+ diesels. Engines, such as the OM617, pre 86 models anyway I think, (I dont know if the early W201 190D is excluded) need valves adjusted manually.
-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.