GOTCHA!!
Got the radiator back from the rad-shop today and bolted it in. She is finaly cool now. The needle reads a steady 180 no mather what I do.
First I never thought it can be the radiator. It never gave me trouble before plus I had it cleand and roddet out 2 times.
When they took the core out I could see how bad it was.
Now they welded in a modern core with more than twice of the cooling performance.
Thanks for all the good information and brainwork.
All the best from sunny southern Germany, Frank