I have a 2000 ford taurus with a 3.0,one day it was leaking fluid so I took it to my mechanic, he put a pressure test on it and found nothing leaking, changed the thermostat and flushed out the system,it does`t overheat but the hose going from the radiator to the thermostat gets rock hard when you rev up the engine.He has never run across this before and thinks that the head gasket is gone which is puting pressure into the system. Has anybody come across this problem?