Hallo Uwe,
ausser Kühler und ZKD, könnte da nicht noch ein Motoröl/Kühlmittel-Wärmetauscher am
Ölfiltergehäuse (undicht) sein ?
(Leider auf English)
There is no oil/water cooler in the oil filter block. There is an oil/water cooler in the main radiator on the drivers side tank. Look down near the steering pump and you will see the two hoses. This cooler can leak oil into the coolant.
Usually, the cooler leak is more likely than a head gasket leak. However, you did overheat the motor. When my OM606.964 overheated it stretched the two head bolts between cylinder 1 & 2. Those are also the ones close to the oil passage. In my case it leaked combustion gasses into the coolant only if I drove it hard. Your engine might be leaking oil into the water instead. The passages are very close together.
The problem lies with one or the other. Very hard to say which to try fixing first. If the head gasket is original, I would suggest replacing it before the radiator.
