I have a 2004 H2 and I am getting overheating indications on the driver corntrol center and the heat gauge. It was fine when I drove it home and the next morning at 2am when I started for work it overheated with 5 miles of home. I have changed the thermostat, the water pump, the fan clutch and the coolant cap and it still overheats. I am desparate. Any ideas?

 

Hello,
You may have an internal coolant restriction...you may want to power flush or reverse flush out your coolant system.
There is a coolant flush system available by "Prestone" which includes a "TEE" adapter, when installed in-line to the heater inlet hose line, you connect your garden hose to it and using the water pressure from the hose and your vehicle in idle, it may dislodge any restrictions in the system.
-OR-
Since you've practically rebuilt the cooling system, you may have a missed something which is exclusive to the Hummer designed cooling system.
-OR-
If your vehicle is not actually showing any adverse heating effects, you may have a faulty heater/indicator sending unit.
Keep us posted on your progress.
Safari Hummer H2

 

check the fan clutch. get it hot and grab some rags and whille the engine is at idle try and stop the fan with the rags if it does stop the clutch is bad

 

Okay, you aren't going to believe this. I changed the thermostat, the radiator cap, the water pump, the fan clutch and the sensor and it still overheated. I refused to believe that it could be the radiator because it came on so suddenly. No gradually becoming less efficient at cooling, just wham. I didn't believe it could be the head gasket because I had no water in the oil or in the transmission and no steam coming out of the tail pipe. So before I got serious about the heads I pulled the radiator and had it rodded out. The main part of the radiator was fine but the nipple for the small hose going to the overflow tank was plugged. (it only has a small orfice deep within.) When that was unplugged the problem went away. I drove it for over 2 hours today in 100 degree plus temperatures with the ac on and a lot of idling. Temperature was rock solid.

 

Truly bizarre. I never would have guessed that one. Glad to hear you finally got it sorted out. Well worth making a mental note of this one.

 

it could be the thermostat is stuck and/or not operating properly. have your dealer check it for you before it cause you big problem.

 

glad you found the problem ,that was a weard problem ,thanks for letting us know what it was ,,btw if you off road and get dirt in the front of your hummer you will have to rinse out the outside of the radiator , but you probley know this , i just thought i would repeat it ...mike

 

Hello,

First i want to say many thanks to rkhal! That what he say is true. Today i fixed my Hummer H2 2006, 55000 km. /overheated yesterday/.without any parts only with one 1 mm wire. You must remove the small hose left above the radiator. Inside was a small holle, completly full with something very hard. After i pushed the wire, the truck made a "deep breathing" and after this i added 1 liter more cooling liquide /there was no place in the tank before i pushed the wire/.

So i drove my truck today 4 hours without any problems and there is 100 % no other problem!

Thank you rkhal!

Best regards from Bulgaria!

 

I had the exact same problem after changing everything that you changed. The guy who rodded out the radiator found that little orfice in the overflow nipple clogged and when that was cleaned the problem went away.