Just purchased my H3 two mths ago, so we are still 'getting to know' each other... Have noticed temp gauge routinely hangs around 1/2 way mark sometimes little over; however, this summer as we've moved into solid 90+ temperatures, have noticed quickly ramping temps esp. with AC running. This is during open road driving; coolant is full; no leaking [less condensation] and everything outwardly appears to be fine. I immediately turned off AC and put windows down - seemed to resolve.

Getting ready for road trip to beach with same temps predicted ... concerned. Is this a routine situation? And tips? Please advise! (thank you)

 

Normal.

I have found in my short period of ownership and looking at these forums, this is a common question.

I have a ScanGaugeII and the temp reads in degrees. The normal is around 190 which is probably the thermostat open temp. I have seen mine go to about 215, while the mechanical gauge still reads in the middle.

If you want to really worry, look at the temp for the transmission fluid. At operating temp with these high ambient air temps, it runs about 10 degrees hotter than the water temp.

I was really worried about it initially, but figured that the engineers who built the Hummer H3 probably are pretty smart, so the Dexron VI will handle the temps. I plan on changing the ATF every 50K miles.

In short, let me say, welcome to the forums, H3 ownership and get that Hummer off-road and dirty! Wash, rinse, repeat.

Cheers, Doug in Colorado

 

This was NOT a FAQ!

W/o the mileage on your 06, got no tips for you.

Change the ATF, Filter, and do a radiator flush and refill with fresh Dexron 50/50.

Do a "search" for more info.

 

Oh, sorry Doc... Mea Culpa.

I have seen this question at least 4 times in the past month. Could be because I look at three or four Hummer forums.

I know that today my ScanGaugeII was reading 188 degrees and the needle was dead in the middle, on the line.

My ATF was changed/flush-filled 30K miles ago (18 months ago); the Dexcool was changed 20K miles ago (1 year ago). Oil was changed 2 weeks ago.

The transmission temp was 198-200 degrees. Outside temp 88 degrees.

Intake air temp was 140.

No offense but Dexron VI ATF should not be 50/50; it should be 100%. Dexcool should be 50/50 however, since 100% antifreeze/coolant is not the most efficient.

Cheers, Doug

 

Check the 50/50. But how many miles on your truck?

Two possibilities. There is a TSB regarding guage cluster replacement if the Temp guage reads higher than normal and the actual temp is within the acceptable acceptable range. 188 on the scan guage is what they would tell you is normal (within 5 degress +/- of the T stat temp).

The other is, your Trans is hot, depending on how many miles, trailer towing history, it could be time or close to it for a rebuild?

Best of luck.

 

I had a large write up about this a while ago because it bothered me. I did a lot of things to get the needle to stay in the middle but I have only half way solved my issue with the heat.

I went out looking at different vehicles my friends own and found a few things about other vehicles ranging from rear wheel drive cars to chevy trucks.

Facts:
1. The H3's radiators are so close together that you can barely fit a butter knife between them.
a. After looking at the other vehicles, there is a good 2-3 inches of space between the A/C rad and engine rad.

2. The H3 only has the engine fan pulling air through both radiators
a. 3/4 of the other vehicles had an electric fan in front pushing air while the engine fan sucked cause more air to pass over them.

3. The H3 transmission cooler on the bottom of the radiator is very small even compared to the smaller RWD cars I looked at.
a. Most of the other cars had an external stock tranny cooler.

4. My temp gauge never and I mean NEVER goes above the mid mark if the A/C is off. This includes if I am offroading up and down hills. Only when the A/C is on.

I am convinced that when the A/C is on those hot R-112 gasses going through the A/C radiator combined with little to no space in between them plus the inadequate tranny cooler on the bottom is the major contributor to this H3 cooling issue. I scanned the truck and at 100 degrees outside, A/C on high the scanner reads 230.

I am in the process of moving the A/C radiator back 3 inches and see what that does. If that helps I might think of including an electric fan similar to whats on the chevy trucks that will relay to the A/C system.

 

Thanks for replies.. it's got 48K - not towing, just me and truck - changed oil, filters (oil/air), & topped off fluids; GM dealer checked out completely when I bought which was not too long ago(?!) Anyway, just went to beach & same issue - ramping up to 3/4 mark - made me nervous! Again off with the AC -not a pleasant trip. I may be overly gunshy due to just got rid of LandRover with overheating issues-lots of money & down time & same initial senerio = little 'notice' before blowing up high $ items. Not interesting in doing that again! Agree with radiators too close - if you move, update us! Will definately flush & fill - can't hurt & then I'll know what's in reservoir.

 

Thanks for replies.. it's got 48K - not towing, just me and truck - changed oil, filters (oil/air), & topped off fluids; GM dealer checked out completely when I bought which was not too long ago(?!) Anyway, just went to beach & same issue - ramping up to 3/4 mark - made me nervous! Again off with the AC -not a pleasant trip. I may be overly gunshy due to just got rid of LandRover with overheating issues-lots of money & down time & same initial senerio = little 'notice' before blowing up high $ items. Not interesting in doing that again! Agree with radiators too close - if you move, update us! Will definately flush & fill - can't hurt & then I'll know what's in reservoir.

 

These trucks look like they run hot according to the temp gauge. Normal.

 

thanks.. was feeling that with replies.. just wanted to verify - appreciate it!