So finally after all the effort of looking at the radiator, thermostat etc, it was the "joint de culasse" engine head gasket that was used and a change not only took care of theoverheating issue but also the automatic gear box is real smooth and the whole car seems to be stable. Before on turning off the ignition the engine would sputter for a few seconds but that too is gone. It was expensive but who cares.
The little side story. First the gasket changed, had to take the car back because it still overheated and the garage discovered that a 230 Sl gasket had been used and finally it was found that the gasket for the 280 SL USA is different from the European model. All fine now.
Thanks to all who helped with their input and in particular Joe and Cees. Yes Cees, Where do we stand with the poster? Christmas present?
Ashok
280 SL
White Grey US Autom.