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Old 07-31-2008, 09:58 AM   #1 (permalink)
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H1 Tires Going Flat Question

One Of The Ladies Here At Work Has An H1 And In Around 4 Hours Both Front Tires Go Flat. The On Board Air Fills Them Back Up But The Problem Is Still There. I Did A Quick Google Search And Came Up With A Post On Another Site That Said The Schrader Valve Next To The Compressor Was Bad So We Checked That And No Air Leak. In The Time That We Where Messing With It The Tire's Lost 4 Psi. Does Anyone Have Any Idea What It Could Be? Any Help Would Be Great. I'm Hummer Dumb But I Help When I Can
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Old 07-31-2008, 10:05 AM   #2 (permalink)
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ok, here is what you want to do--Are you in Dayton NV--we have a few hummers finishing the Vegas to Reno Pre-run in Dayton Sunday afternoon, meet us there and we'll take a look

Fill up the tires--un-plug each tire from the CTIS system at the wheel

they wont go flat now--unless there is a hole in one of the tires

at your liesure start plugging tires back in and looking for hose or fitting leaks from each tire back up to the compressor and valve package

other possible leak points are little plastic hoses that go to the guages --they tend to break, and will leak out your system.

http://www.humvee.net is the real hummer technical forum

www.flashoffroad.com has a great tech section on chasing down leaks also
Rob Everhart BITD #8052 Race Hummer Old Monster Garage Truck #52

Last edited by reverhart; 07-31-2008 at 10:07 AM.
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Old 08-09-2008, 07:25 AM   #3 (permalink)
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My first spot to check would be the gauges. Those lines are most often the culprit. It would be a good idea to check the tires themselves first to make sure that is not the issue. Any update on the issue?
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Old 08-09-2008, 10:37 PM   #4 (permalink)
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Well the leak is basically one of the following items:

2-quick disconnects
3-something on the compressor or manifold

What year is the H1? This is very important since the air system changes from different model years. 92-95 uses, I believe the older HMMWV style value system operated by leaver on the inboard tunnel wall near your right leg.

96 upwards, uses a switched system using 3 solenoids to operate a manifold to inflate and deflate the tires.

To get my system air tight [I just returned from a trip to Canada for 3 weeks and left my system connected at 40psi, and the pressure held when I returned].

This is what I did:

I have a 98 with a switched CTIS system, so I disassembled the inflation and deflation valves and cleaned them. I replaced my 10 year old wheel connectors with new CTIS fittings that should be available to the public soon from a well known hummer vendor. I replaced a leaking spindle seal that keeps gear oil and air seperate in the hub assembly.

Finally I replaced a faulty front axle solenoid.

Now my CTIS system is rock solid, and it ran me about 300$ in misc parts and a bit of time with a spray bottle of soapy water to test all the air lines and fittings.

So to check your problem, I'd get a spray bottle, and mix in a soapy solution of dish soap and water and spray the hub's air lines, check for bubbles in the soapy foam.

After that you can do the soap test on the opposite side of the hubs, from the spindle to the T-junction where both front wheel's airlines connect. Then check the front axle airline to the valve or CTIS manifold.

Once you locate your problem then you figure out how to fix it.

It could be a busted hose, a bad seal, a solenoid thats sticking "on" leaking out air, etc.

What year is the truck?
1998 AM General H1 HMCO Model 90 Turbo Diesel
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Old 08-10-2008, 07:35 AM   #5 (permalink)
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A spray bottle and soapy water are your friends.
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Old 09-12-2008, 01:15 AM   #6 (permalink)
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The soapy water as mentioned is the good thing.

Not applicable here because it's only the front system that's leaking but a possible source if all 4 are is the pressure relief valve. If you let the pressure relief valve get used too much the ball in there and its seat will get some flattening and not seal as well.

The last time this happened to me I took the valve apart and removed the steel ball bearing in there. It looked more like a geodesic dome than a bearing because of all the pounding it had gone through. I went to the hardware store and bought a new bearing. I took the old steel ball and used some super glue to glue it to a small 12" length of brass tubing. The next day after it has set I coated that old steel bearing with valve lapping compound. I then used the old steel ball like a lapping tool (spinning the brass rod between my palms while the ball bearing was seated in the valve body) After a few minutes I felt like I'd done a good job of smoothing out the seat of the valve I removed my crude lapping tool and then washed all the grit out of the body of the valve. I then coated the new steel ball bearing with a light coat of grease and reassembled the valve and it has worked like a champ. Needless to say I'm very careful now when inflating my tires because I don't want to get that valve leaking again.

More applicable to the problem:

A leak I have in my system now is the front right CTIS wheel connector which leaks when the tire is hooked to the system but not when it's disconnected by releasing the connector. That leak is loud enough to hear when I'm down by the tire. That should not be a big deal to replace. But the soapy water technique would not work if I sprayed it on that connector if it was in disconnect mode. So be sure to spray those both connected (pushed in) and disconnected (popped out) or you might miss the leak.

Last edited by Vanishing Point; 09-12-2008 at 01:17 AM.
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