I have an 86 Trooper with an overheating problem. It never really overheats, but it runs all the way to the right on the operating range of the temp guage. The engine has been overhauled and the head gasket is good. The only things I can think of are the thermostat possibly stuck restricting the full flow of water to the engine block, a weak water pump, or a weak radiator. There is no great coolant loss or overflow loss.

 

now, when it is reading as overheating, is it actually overheating? are you sure that the temp sending unit is good?