If someone could please give me an idea as to what could be causing this, I would certainly appreciate the advice.
Am taking the vehicle to a tire store tomorrow. However, where I live there are very few places that even understand the air pump/tire inflation system on an H1 Hummer. Most places here are clueless on how to remove the tires.
P.S. So am I- do they have tubes??
Thanks for your help!

 

Don't let anybody who doesn't have a clue screw up your truck. Air your tires up to normal pressure and disconnect the front two tires from the system. There is a quick disconnect at the wheel. Just depress the button on the side of the valve and it will pop off. See if the tires still leak down.
It would help to know which wheels you have, year model of truck, etc.
You might also first check that both of the valves are seated firmly on the wheels first. Sometimes when they get worn they can pop off or loosen.
Also try airing up and releasing air several times in a row. Sometimes the main valve can get stuck or get debris stuck in it and won't close all the way.

 

Thanks for your reply. The other two times I had issues with this vehicle you were the one that directed me to the correct fix.
So I have a '97-1/2 H1 Four-door open top 6.5 Turbo Diesel. The first tires that were on the truck were a military version radial 37x12.50 R16.5 LT. At 18,000 miles on the odometer I put on 4 new Parnelli Jones radials, same size as I was driving cross country and not sure of the set that was on the truck when I bought it in CA. Now the odometer reads 30,500 so these tires only have been driven 12,500 miles- on a sandy beach and all local mild travel.
I disconnected the CTIS from the front tires as you suggested. The left front one worked just as it should. The right one was a little sticky and once I disconnected it could not snap it back on (are you supposed to be able to reconnect to the CTIS?) The low pressure alarm came on. So now I am waiting to see if the front tires lose pressure again.
Thanks again for your help and will follow up w/report on air loss.

 

After I disconnected the front 2 tires from the system, manually put air in the tires, no problem w/the front left tire. The front right's valve stem is leaking and that may be the problem. I put the valve stem cover on and that temporarily stopped the tire from hissing/losing air.
How do you replace a valve stem without taking the entire tire off? Are the valve stems for the 37 x 12.50 R16.5 LT readily available?

 

Haven't looked for them but I would think most big tire shops would be able to help you with the tire stem. Which wheels to you have, Cepek, steel, factory aluminum one or two piece?
Sometimes the quick disconnects get sand/dirt stuck in them. They also have little O rings in them that can go bad. They can be rebuilt or most Hummer vendors sell them. They should go back on rather easily. Cepek CTIS hoses connect a little differently than the OEM version.
I see you are on HML. You will get lots of good feedback from the group there.

 

As to type of wheel I think they are one-piece steel. I am fairly sure they are not run-flat although the wheel rim has two concentric sets of bolts- 12 in the outer diameter and 8 in the inner.
A displaced little o-ring sounds like it could be the problem in the one tire that is leaking at the stem. For the time being, the plastic cap is doing fine keeping air in the tire but I don't expect that to last long. Please give me name of an on-line Hummer supplier for them and rebuild kits. Sand may be the culprit- I should probably redo all 4. What is an OEM version? Is Cepek an after market adaption? The vehicle is factory "stock" i think.

And remind me what I joined- what is HML? Thanks again for all your help and your time.

P.S. One more thing, how do I turn off the Low Pressure Indicator alarm now that I have disconnected the front CTIS? It's starting to annoy me :-(

 

Tustin Hummer in Tustin, CA ((Mike)or www.hummerpartsguy.com.( Dave) can take care of you on the quick disconnects. Dave had them on sale not long ago. Cepek stuff is great but not OEM. Not an issue as his stuff is designed to meet or exceed OEM specs. They just connect differently.
HML aka Humvee.net. Might also check out Flash Off-Road Photography, Hummer Accessories, Hummer Maintenance, Modifications and Tech info

 

Time for me to make some calls. Thanks again for your help.
1hummer w/3goodtires