CTIS Quick release/dump valve needed

[PowerstrokeNC]

Anybody have a source for these? thanks for the help.

 

[hklvette]

While it doesn't look the same, you can get QR valves at NAPA. Need to know the in and out thread sizes (in is in the center, out on the sides). I can get part numbers tomorrow afternoon, as I have some lying around.

 

[PowerstrokeNC]

While it doesn't look the same, you can get QR valves at NAPA. Need to know the in and out thread sizes (in is in the center, out on the sides). I can get part numbers tomorrow afternoon, as I have some lying around.

Have you used these before in lieu of the "CTIS" version? If this will work, I am all in, thanks for the help.

 

[Suprman]

The m939a2 dump valve looks the same it may work. I can tell you that they don't go bad often. A system air leak like a bad hub seal will mimick a bad valve.

 

[PowerstrokeNC]

The m939a2 dump valve looks the same it may work. I can tell you that they don't go bad often. A system air leak like a bad hub seal will mimick a bad valve.

I used the TM troubleshooting steps and found the rear one on my truck to be 'leaking' each time the CTIS did its cycle. Air was coming out the dump tube on it.When I checked the front one it didn't leak. So I am assuming this is bad. I actually plugged the dump tube with an old cork and was able to find another leak on the left front wheel.

it does look like the same one as on the 939 trucks...I just can't find any around for sale it seems.

 

[Suprman]

I will look I have one somewhere. Yours probably isn't bad though. The wheel leak is causing the valve to see less pressure and it thinks it should dump. If you fixed the wheel leak the problem should go away.

 

[PowerstrokeNC]

I will look I have one somewhere. Yours probably isn't bad though. The wheel leak is causing the valve to see less pressure and it thinks it should dump. If you fixed the wheel leak the problem should go away.

Thanks for looking for the part.

I will try your suggestion and see what happens. So the wheel leak on the front can affect the dump valve on the rear? Or you are saying the wheel leak is the main cause of the fault and the leak on the dump valve is a minimal consequence? I did notice the dump valve to be leaking what I would call a 'fair' amount whereas the wheel was really leaking much more aggressively.

 

[Suprman]

The whole system is one air line in and it splits off via a quick release valve on each axle, which all 3 are daisy chained. When the system sends pressure to fill, if a tire has less pressure then its less resistance to incoming pressure and that tire will fill. If all tires had equal pressure say 50 psi and the system sent the 120psi system air then all tires would inflate equally. If there is an air leak somewhere, like a hub seal, the system is supposed to pick that up when it does the initial pressure check and alert via the control lights. But that does not always happen. When the system starts airing up the tires, if the leak is great enough so the quick release valves see only around 25psi they will open and dump air. Its all mechanical. If you have a really big leak and the wheel valves see around 15psi then when the system thinks its inflating the tires you will actually be deflating tires. I have seen both of these scenarios happen.

 

[hklvette]

The whole system is one air line in and it splits off via a quick release valve on each axle, which all 3 are daisy chained. When the system sends pressure to fill, if a tire has less pressure then its less resistance to incoming pressure and that tire will fill. If all tires had equal pressure say 50 psi and the system sent the 120psi system air then all tires would inflate equally. If there is an air leak somewhere, like a hub seal, the system is supposed to pick that up when it does the initial pressure check and alert via the control lights. But that does not always happen. When the system starts airing up the tires, if the leak is great enough so the quick release valves see only around 25psi they will open and dump air. Its all mechanical. If you have a really big leak and the wheel valves see around 15psi then when the system thinks its inflating the tires you will actually be deflating tires. I have seen both of these scenarios happen.

To answer Powerstroke's question, yes I have used off-the-shelf QR valves in place of the military ones and they work just fine. That being said, Suprman nailed this. On my truck, one of the hub seals had worked its way toward the center of the hub since the truck was driven without the CTIS functioning. This caused a shrill leaking sound like a deflating balloon. I found it by clamping the air line going to the hub from the QR valve, which stopped the leak. When the rest of the tires got up to around 35psi, I released the clamp. The sudden inrush of air seated the hub seal, and I haven't had a problem with it since.

 

[PowerstrokeNC]

This info is really helpful! I am going to focus on the wheel leak and see what happens, will report back.

 

[Ohiobenz]

Is the poppet supposed to move in these valves? My LMTV has a Midland-Grau QRV that is all plastic and has no hose connection or tube outlet. Removing the inlet fitting shows what appears to be the poppet but it is not movable....