tires or CTIS leaking?

[Deuce007]

I am sure that this has been gone over time and time again but how can I tell for sure whether the tires or the CTIS is leaking on an m35a3? The back two tires are the ones that leak the most, they leak out in one day and the others take about a week. First, I sprayed the tires with soapy water and had no luck. Then I sprayed all of the air lines that I can find connected to the back tires and found no leak I have removed the protective cover from the wheel so I can see the wheel valve and sprayed that with soapy water and that doesn't leak air either. So can anyone tell me the best way to verify whether the tires are the problem or something in the CTIS.
I know that someone is going to say shut off the CTIS but does that mean that I just shut the truck off?. I have already manually aired the tires up with the truck off and still had the tires go flat so does that mean that they are the problem?

 

[Derrickl112]

Unplug the ctis at the tire and cap it off.

 

[Rustygears]

99% of the time the source of A3 slow leaks is the rubber grommet sealing the fill stem (pipe) to the rim. This little rubber SOB is about the diameter of a quarter and rots out. The only way to replace is to pull the wheel and dismount the tire completely. Cheap part but a total pain to replace because of the tire dismount/mount fun. Many people blame the rim O ring sealing the upper and lower halves of the rim, but these seldom leak if installed properly.

There's many posts on the grommet and the proper procedure to refurbish & reinstall the grommet and O ring. I've done 4 of mine and no more leaks, even with CTIS fully connected. The wheel valve fully isolates each wheel from the CTIS system and there is no pressurization of the plumbing or axles when CTIS is not operating. Those wheel valves seal well. In fact a bigger issue is getting the CTIS to open them.

 

[Deuce007]

99% of the time the source of A3 slow leaks is the rubber grommet sealing the fill stem (pipe) to the rim. This little rubber SOB is about the diameter of a quarter and rots out. The only way to replace is to pull the wheel and dismount the tire completely. Cheap part but a total pain to replace because of the tire dismount/mount fun. Many people blame the rim O ring sealing the upper and lower halves of the rim, but these seldom leak if installed properly.

There's many posts on the grommet and the proper procedure to refurbish & reinstall the grommet and O ring. I've done 4 of mine and no more leaks, even with CTIS fully connected. The wheel valve fully isolates each wheel from the CTIS system and there is no pressurization of the plumbing or axles when CTIS is not operating. Those wheel valves seal well. In fact a bigger issue is getting the CTIS to open them.

when I sprayed the wheel valve with soapy water would I have noticed that the grommet leaks or is it usually hard to spot?

 

[Deuce007]

What would be my next step? would I just cap off the valve (left) with an end that will hook up to an air chuck? Also when I put it back together do I just put thread lock glue on it? Finally, will the same 90 degree brass angle in circle on right fit on the pipe (left circle) that I will cap off?

 

[spicergear]

My M931A2 kept having one tire go down. It was actually the O-ring between the wheel halves on the combat wheel. I happened to catch it one day it was raining and saw bubbles at the large hole for the valve stem to stick though the outer retaining ring.

 

[glcaines]

As Rustygears stated, the leak is almost certainly the valvestem grommets. I would not disconnect the CTIS as it is a good system that seldom leaks. Bite the bullet and pull each wheel and replace the grommets. Eric's has them, as well as new o-rings. Make sure you tighten the nuts to 45 - 60 Lb-Ft. I would also recommend getting new nuts for the valve stems from Eric as they tend to get rounded off by the socket when loosening and tightening. Be careful with the wheels as a complete wheel-tire assembly on an A3 weighs in at 385 pounds and it is easy to get hurt or also strip the threads on the lugnut studs.

 

[Rustygears]

Yup. Gary's dialed in on this one. There is a beautiful document that exactly describes how to pull the tire off the rim correctly, cheaply and safely. Someone posted it and I updated it to add some extra details. Do a search and it will pop up. You can do it one man. It's a clever method using an engine hoist for all the heft. You will also need a pry bar, a 3/4 breaker bar for the rusty rim studs and a bunch of liquid tire lube. That's the magic juice. Use it to both dismount and mount - tons of it!

 

[spicergear]

T'wer I all hubs out like an A3, I'd try to leave the wheels on the truck if possible so less to mass to have to handle...

I would have done this with my 1400x20 I just had to change off the rear of my tractor...CTIS and hubs in.

 

[Deuce007]

If you guys go to TM 9-2320-386-24P page 120 could you guys tell me what numbers of the parts do I need to replace. ex 11 PAOZZ 5325014375810 2W783 RG22 .GROMMET,NONMETALLIC................ 1

 

[glcaines]

I have attached a information from Erik's Military Surplus site as he has all the parts you need and he is very reliable. In my opinion, you should order the following items for each wheel.

Wheel O-ring: 12363606
Valve Stem Grommet: RG22
Valve Stem Nut: HN80

I also keep 2 -3 extra of these parts in the truck for emergencies, as they are not readily available at civilian parts houses. Erik's URL is http://eriksmilitarysurplus.com/ . I also modified a deep socket for the nut by grinding the face flat to assist the socket in getting a grip on the nut. Make sure you use a hex socket.

 

[Deuce007]

Would I be able to see if the grommet/ o-ring is leaking with soapy water or is it one of those guess and check moments?

 

[1 Patriot-of-many]

Would I be able to see if the grommet/ o-ring is leaking with soapy water or is it one of those guess and check moments?

Yes you would. bend around the back of the tire and spray around the grommet. Also spray around the hole where the tube goes through the rim. If you get bubbling in the hole, it's an ORING(where the two rims meet). If you get bubbling at the grommet, it's the grommet. Either way you'll have to break down the rims replace the oring and the grommet while it's open. I paid $40 each for two of mine at a local shop+ orings and grommets from ERIKS.

 

[Deuce007]

Ok, I finally found it. It was located in the hole between the pipe and the rim. How much work is it to repair the leak. I need to unhook CTIS, remove wheel, seperate wheel and rim, switch o-ring, reassemble wheel and rim, put wheel back on, hook up CTIS. did I miss anything?

 

[1 Patriot-of-many]

Ok, I finally found it. It was located in the hole between the pipe and the rim. How much work is it to repair the leak. I need to unhook CTIS, remove wheel, seperate wheel and rim, switch o-ring, reassemble wheel and rim, put wheel back on, hook up CTIS. did I miss anything?

Yep Oring. A lot of work. Best to replace the grommet too and possibly the nut for the grommet while you are at it. Use the TM. Proper torques are crucial on the rim nuts. Also while the rims are seperated examine the groove the oring sits in. My second wheel had to be done twice. Had to be sandblasted because some grunt used some kind of RTV sealant in the groove. Also make sure the oring is lubricated with the proper stuff via the TM. Not OIL.
If you don't have a 600lb torque wrench, buy one. The rim nuts are like 425-475 ft lbs for proper torque.

I've gotten all the nuts off but never split the rims. It's a chore. Both the leakers I had I took to a local shop after taking all the CTIS crap off and removing the rim nuts with an air gun. $40 a piece. Well worth the the money.

 

[Rustygears]

Try this link to the post for the detailed tire change procedure: http://www.steelsoldiers.com/attach...change-procedure-a3-tire-change-procedure.pdf

Hat tip to mktopside for this rosetta stone of A3 knowledge.

 

[flyxpl]

I noticed in one pic the tire is flat , you do not want these heavy trucks to sit on a flat for any period of time . It will ruin the tire and you will have a blowout . put some blocks under the truck to keep it of the ground until you get leaks fixed .

 

[glcaines]

Also, when you dismount the wheel, mark the hub and wheel to make certain that you put it back on in the same orientation.

 

[Deuce007]

Also, when you dismount the wheel, mark the hub and wheel to make certain that you put it back on in the same orientation.

That reminds me, the wheels on half the truck are backwards so when I put everything back together could I turn it around so it is facing the right direction?

 

[spicergear]

Yes, it's yours now...put the tire how you want them; or how they look the best.

From sitting some water/rust had made it to my O-ring on my tractor and caused a leak exactly where you're is. Just changed it out. Something else that I do just to help make sure the seal is good is I put a bead of tire slim on lower part of the retaining lip on the wheel then around the big O-ring too. That way you're pretty well rest assured to get a positive seal and not have to tear it down again. Make sure everything is clean, yes...but I don't feel a bit of redundancy hurts a bit!