Hi Scotty,
I have a 2007 H2 Hummer with a rebuilt engine and a new transmission, which was replaced 30,000 miles ago (the original had 230k). Everything worked fine until recently, when I noticed that if the engine idles for more than 10-15 minutes, the temperature starts rising above 240°F. However, if I turn the AC off, the temperature returns to normal operating levels.
I've replaced the fan clutch, thermostat, and water pump (all OEM parts) and I've flushed and bled the coolant, but none of these changes made a difference. I'm out of ideas on what to check next. Another thing I noticed is that when the engine idles for 10-15 minutes with the AC on, as the temperature rises, the AC becomes less effective, and the air being blown gets warmer.
Could this be an issue related to the AC that's affecting the engine temperature? Any thoughts or advice would be appreciated.
Thank you!
Overheating and AC weakening at idle are typically symptoms of inoperative electric cooling fans but it appears that model has only an engine-driven fan.
Is the fan shroud missing? Is your radiator clogged?
