97.5 TD. the heater is nice and hot...well as hot as i would expect from a Hummer. But when I get out on the road it slowly starts to cool off to where it is just blowing ambient air temps. when I come to a stop of get off the freeway, it slowly warms back up. I dont have a lot of expierience with HVAC systems but Im pretty mechanically inclined. any suggestions?

 

Not a mechanic but in my 97.5 I used to have I had to do the heater upgrade as early heaters would slowly start to fail. What you described is exactly what mine started doing at about 50k miles.

I think is was a heat core they replace? not too expensive. If I recall around $500 plus labor

 

mine is the 97.5 also. I thought this already had the HVAC upgrade? oh well. I had a feeling it was the heater core. I do all my own work, do you remember how much you paid for the parts only?

 

I do not it was way back in 2000 when I had my last H1. sorry man. I am on the search for a new one now. You may have a different issue?

 

might have found the problem. My low coolant sensor it bad and the light stays on all the time. well i started thinking about it and thought maybe it was low on coolant. At highway speeds there wasnt enough coolant to be pumped around. Sure enough the res. tank was empty. I was so use to looking at that low coolant light, that i never really checked it after a6 months of it staying on constantly

 

Nice, that is alot better that a new heater core. good work

 

just 6 mo huh.
and if i had a h1 id hug it every day

 

@drtom, yes, 6 months. I'm not an idiot yuppy H1owner who bought as a social statement. I do all my own work and use mine for what it was designed for. The sensor has been bad for bout a year. After keeping my eye on the level for a while, and never having any problems, I got tired of checking it. I maintain my Hummer the way it should be. I have been driving these things since I was 18 when I enlisted in the army, I know them pretty well. Its not like the truck would spontaneously combust if the coolant got too low. There would be tell tale signs.....the first and most obvious being overheating, especially t highway speeds. Which it wasnt doing. Thanks

 

Joe,

Did you bleed the coolant system after you added the coolant? If it was that low you may have gotten some air in the system. Let it get to operating temperature and open the bleeder valves until you get a solid stream of coolant out of the valve. Do them one at a time. One of the valves is at the back of the radiator on the passenger side and the other is on top of the engine. All it takes is a flathead screwdriver.

 

I always bleed the system of anything that I service. My motorcycle is a pain to get to the plugs. Guess the Japs don't expect their motors to ever need cooling system service. Lol. Thanks for looking out though bud