Hello everyone. I have a 95' GMC Sierra, 5.0 extended cab, 2wd. I am having a problem with it overheating, only when I go up any hill. I can run it wide open 85-95mph no problems, loaded or unloaded. Anytime I go up hill empty or loaded the temp flies up, if i dont run the heater it will most likely overheat. I have rebuilt the Radiator and replaced the heater core, (it leaked into the cab) the thermostat is not the problem according to the mechanic I saw. Please help. If I replace the fan clutch would that do anything? Thanks for any input.

 

how hot we talking?....and how cool otherwise?

 

The truck runs normally at I would say 195 to the halfway mark. This includes running at 75-80mph.

 

As for how hot it goes all the way to the limit unless I switch the heater on then it will go back down to the halfway mark. Thanks.

 

its either low on water...or the gauge is wacky...i think it may have air in it

 

Sorry, air where? I am certain it is not low on water I am consistant on checking the fluids.