Ok, i tried what i read on all the forums and still at a loss. (literally) My rear tires have been leaking down 10-15 lbs in an 8 hour period. Everytime i get in the truck, i have to add more air. Using more air then Diesel. (not really).

I did the self test by releasing the CTIS air lines and pumping the system up to 40 lbs. I actually disconnected all four lines. Checked the pressure on all 4 wheels and the gauge. The next morning, both rear tires were down, and the gauge was down also.

Dont really know what is going on. I will say, the air loss is getting worse.


Anyone have any ideas?

 

If the ctis valves are poped out and the tires leak down over night the leak is in the wheel( most likely the 2 piece rim oring or you have a hole in a tire) & or the ctis wheel valves are leaking. Hummer parts guy has them on sale. If you have the valves pushed in (so you can inflate/ deflate them) and only the rear leak down then the leak is on the rear of the system. Get a bottle of windex or soapy water and spray all the air system down. If no bubbles are found then remove the wheel hub vent lines and listen for or feel a air leak by holding your finger over the vent on the hub for a minute. That will be a spindle seal. Easy to replace if you know how to properly adjust the wheel bearing preload(so the wheels don't fall off) and have a tiny pair of snap ring pliers. If you hear air leak coming from the Engine air filter area then you have a spindle seal leak in one( or more) of the hubs causing air to be pushed into the vent line which connects into the air filter housing or the manifold valve is leaking into the supply line. The inflate/ deflate valve in the manifold can stick also.
Let us know.

 

Ian pretty much covered it.

 

If you replace the hub spindle seals it requires removing the steering arm cover, i like to pop the ball joint so you can remove the cover to clean it easily & it makes it easier to reinstall the cover straight so you dont tear the new seal. I was thinking about the hub spindle seals you have to adjust the bearings. To do just the spindle ctis seals you dont have to touch the bearing nut. Order one spindle ctis seal and the hub fill washer per hub. Also order extra hub access washers cuz there nylon(and break like the fill plug washers) and i would call hummer parts guy or big dog offroad and order 4 ctis spindle seals, 4 fill plug washers, 4 access plug washers and some random misc. seals so the part total is at least $25-30 cuz i hate shipping a $1.89 part with $10ish shipping. Use black silicone on yhe cover and Lucas 80/90 oil in the hubs. Install the spindle seals and put oil on them before reinstalling on the hub.