O.K. my brother has a 2001 3.8 auto and are having some strang overheating problems. The car starts and drives normal at first, then the temp hand starts moving toward the red but not touching it. When this happens he turns the heat up high and the hand moves down to normal but the heat then blows cold. And while the temp hand is up toward the red the heat sometimes blows cold but mostly hot. The t-stat has been replaced, there is not any leaking fluids(inside or out of the car), and the coolant is full. What could this be? Where should we start?

 

As a matter of fact my car is doing the same thing right now. Most of the time it is fine but sometimes when I stop for a little bit and one time even when I was drivin it would start heating up so I did the same turn on the heat and it went back to normal. I also bought a new t stat but haven't put it in. Very soon I am going to try to flush it out..it may be from it clogging up so if that don't work then it must be something more serious.

 

check to see if your radiator fan is turning on. It shouldn't run all of the time but should come on when your engine reaches a certain temperature and when your air conditioning is running. Give that a whirl for starters.

 

Check for compression, may have a head gasket issue. It'll be a very slow leakdown, also make sure yor reservoir isn't overfilled, or the system won't clear out air properly. If there's no heat coming out when the heater is turned on then it may be heater core issues.