my 300SD is nearly overheating at high speed driving (i.e. 75-80 mph). Temperature is 100F outside, with AC on (R134), gauge at 110-115-120C, so that I have to slow down to 65 to prevent overheat. New water pump recently, thermostat couple years ago. Also replaced radiator few years ago. Car runs fine at 55-60 mph (95-100C), and similar at idle/city driving. Shouldnt a car normally cool very nicely at high speeds?
What could explain this?
could this be the fan clutch..it is original.