Got an 83 300SD, 165K, pretty good shape. After I had initial rather expensive work done, it developed a wierd roaring noise, intermittant. Sounds like a bearing in the AC or something about to fail.

It comes from drivers side under hood and I notice it at idle. It doesn't cycle with AC every time. It never happens with air off and when noise occurs I shut off AC and it slowly, not immediately subsides.

Replaced compressor, R-12 system and noise re-occured.

Now what, I'm open for suggestions?