You coudl try a thermostat, but pressure check it first to see if there are any internal leaks. Also disconnectthe fan andcheck radiator for cold spots if they have them then the rad needs replacing. It still cold be the head gasket
October, 4, 2012 AT 1:12 PM
Overheating during high speed driving and under load is an indication of inefficient cooling. Check the radiator for clogging.
Perform external test first and if you do not have coolant losses from radiator and drives ok under normal conditions, I don't think it is a blown head gasket.