I would start by trying the thermostat. But it's odd that the engine doesn't warm up and you have good heat. There are thermometers that can be used to test the coolant in the radiator when the engine is hot. I question if the temp sending unit is working properly. You may want to rent or see if a parts store has one to borrow and check the actual temp of the coolant when it's hot. Of course, never open the radiator when it's hot. Open it with the engine cold, put the thermometer in, and let it heat up. It should be around 190 to 205 degrees. If it warms up properly, the temp sending unit may be bad. The reason I say this is because you said you have good heat. If the engine wasn't warming up normally, the heat would be warm at best.
Let me know what you think.
Saturday, February 7th, 2009 AT 5:57 PM