I have a 2002 3.4L with an overheating issue. When driving the temp will reach up to 245F and does not cool down. Originally it was pouring out coolant and since then I've replaced the manifold gaskets and found no water in the oil, replaced the water pump as the bearings were making noises, and the coolant temp sensor. The leak has stopped but sadly the overheating has not. When the A/C is turned on it cools down and stays cool but if the A/C is off it goes right back up and hangs out at a balmy 240F. I haven't had the panel checked to see if it is reading right but the engine is definitely getting too hot to touch. I was thinking maybe the Radiator Fan Control Relay or the Temp. Sensor that would kick the radiator fans on but couldn't find anything for that part. Help?!!??!?!?

 

T-stat?

 

If it cools when the ac is on, I would think that the fans arent kicking on right. The fans come on when the ac is on. Just my thought, also like already said the tstat. I dont know if these cars are hard to get the air out of the cooling lines. My lumina had a issue that it would keep getting hot and I had just changed the coolant. It was air in the lines and I had to put the nose of the car up in the air to bleed out all of the air. It really sound like a fan issue to me though.

 

The t-stat was about the only other thing I could think of. I've gotten out and popped the hood a couple of times and let it heat up beyond belief and the fans stilllllll don't kick on.....

 

Your fan sensor/relay might be going bad, not telling them to turn on, and definitely check the t-stat

 

T-stat is pretty cheap, worth trying that first. It could also be the guage on the panel not reading right (a friend of mine has a Grand Prix with a completely failing temp guage). If you know someone with a scan tool, would be interesting to know the reading.

Also, have you tried bleeding air out of the car?? The T-Stat does not open based on air temp, it needs fluid against it. If you have a bad air pocket, this could be partly to blame. My '94 Grand Am with a 3100 v6 had a problem I was bleeding air out of it DAILY and that turned out to be bad head gaskets.

When the car is cold (has not been running for a few hours), does it idle rough or give you some large clouds of white smoke??