The last time I drove the car I drove it hard up hill for about 1/2 mile and the temp immediately went to 100C. I turned the heater on and drove it mellow for the remaining 1/2 mile home and it stayed at 100C. I parked it with the engine running and felt the lower hose. It was cold. The upper hose was hot and the engine side of the thermostat housing was hot.

I can't believe this is right.

Phil