Hello, I have a 2005 Pontiac Sunfire with a 2.2 Ecotec Engine. My engine started overheating and the air would blow hot when stopped at a red light. I found that my cooling fan was not working. Before doing any more research I switched out the fan and it corrected the issue temporarily. After a couple of weeks it started overheating again a, but not as bad as last time. I switched out the relay and that fixed it, again temporarily. Now when it overheats I can turn on my A/C and that will cool the engine back down. I'm guessing that by switching on the A/C, it forces my fan to kick into a higher speed manually. I think I might try switching out the coolant temp sensor to see if that fixes anything. I believe it might be the coolant temp sensor because my fuel economy has dropped from 320 miles a tank to 280 miles a tank. Any thoughts or insight is appreciated. Thank you.

Hi Derek, I had a similar problem a while back, my car would overheat while idling for long periods, typically at the drive-thru. GM cooling systems have always been quirky when it pertains to the Air conditioning, but my problem was due to a crack in my coolant expansion tank. It wasn't obvious as the crack wasn't in the cooling system proper. Are you slowly losing coolant? have you pressure-tested the cooling system? might be worth a look.