The first step is to determine if the engine is actually overheating. With the engine cool, remove the radiator cap. Start the engine and run until the engine is warm. Stick a thermometer into the radiator and see what the temperature is. If it is too high, then your engine is overheating. If it is not too high, you have a problem with the sensor or the guage.

If the thermometer test verifies that the engine is too hot you will want to determine if the thermostat is working properly. You can remove the thermostat and suspend it with a string in a pot of water. Warm the water and see if the thermostat opens at the proper temperature. If not, replace it (being careful to install the new one in the proper orientation).

If thermostat is opening properly then you have a more involved problem. Either the radiator is clogged and is not providing proper cooling, or the engine is generating too much heat. You can have the radiator cleaned and flow-tested at a radiator shop. If the problem is the engine itself, it may be related to the timing being off or to a vacuum problem. You simply need to troubleshoot these areas.

Good luck!

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Tim--'72 ES, '90 240