ok i have not done anything to the truck except to check the fluid level and i have topped it off...the truck will overheat while its at an idle or low speed...but when you rev the engine it will start to cool the truck off....i have been told this can be many things...bad head gasket,thermostat, radiator cap, or that the radiator might just need flushed...i will try taking the thermostat out this weekend but i need any info anyone has to offer...