Thermostat or belt?


Our 95 Plymouth Voyager overheats only when idling for longer than 10 minutes. Coolant levels are fine. My husband says it’s possibly thermostat, but I think it’s something to do with a belt that squeaks when engine has heated up a bit. Any suggestions for troubleshooting?


Start with the thermostat. It’s the least expensive thing. Replace it. Also check the belt tension, and make sure the radiator fans are working. If the fans don’t come on when they’re supposed to the engine will overheat.

Test the fans this way; Start the engine and let it idle. Let it idle some more. Let it idle until the cooling fans come on or it overheats, whichever comes first. If the cooling fans come on, then it’s probably OK. If the engine overheats before the cooling fans come on, then you need figure out whether the problem is the coolant temp sensor or the fans themselves.

A service manual would be helpful.


Thanks…another thing that started today…the a/c air didn’t feel as cold as it usually does. Is that an indicator of thermostat, the possible squeaky belt, cooling fan, temp sensor or all of the above?


Well, the squeaky belt is not normal and it will not get better by itself. The overheating and the AC may both be related to the belt, or you may have a separate issue. I would start by adjusting/replacing the belt and see what happens.


I think you need to ascertain whether or not the cooling fan(s) are operating. The same fan(s) that cool the radiator also cool the AC condenser, which is located in front of the radiator.

Please verify that the cooling fans are working when they should. If they’re not, you could experience some very costly damage to the engine.


Which engine do you have? The accessory belt systems are different on the different engines.