JD, I had ticking sounds from that area on 2 occasions, both serious. Neither of the ticking sounds near the vacum pump/timing chain cover area were related to the engine temperature...they ticked the same sound level all of the time. I have the old style vacum pump, but the cam follower stuff with the tiny bearings may be the same style as your 84 330 TD, I dunno??.

The first occasion was the bearings on the vacum pump were failing. I found out about this when they suddenly disintegrated and fell into the oil pan while driving. A new pump and that ticking sound was gone.

The second occasion was from the timing chain beginning to disintegrate because the circlip link came off at some point while driving and also fell into the oilpan. Luckily I replaced the timing chain in time so I had no engine damage. The second ticking sound is also gone.

FWIW, I would recommend checking the condition of the vacum pump and then carefully examine the condition of the timing chain. Either one failing could spell disaster.




1979 300D with old-style vacum pump.