So is a malfunctioning oil cooler the only likely cause of this?
There aren't any appropriate Benzes in junkyards around me, I've called and visited (I did find a gasser coupe and looted what I could).

Questions:
*Could I take a shortcut and test my oil temperature after the engine's been driven? What would be a "normal" oil temperature and what would be "too hot"?

*If the oil cooler is in fact not opening (engine oil getting too hot), what's the standard way of taking care of that? Buy a new one?

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1982 240D automatic
Odometer quit at 307K...about 325K now