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Air Brake Service Needed
- Thread starter captcarc
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Is the air being released into the intake with or without your foot on the brake pedal? If it is WITH your foot on the brake pedal you very likely have a bad Q2 valve (located on the backside of the vertical plate just behind the bumper and just forward of the axle.
You might also read over this thread http://www.steelsoldiers.com/showthread.php?126598-M923a2-air-question it also mentions the Q2 valve.
You might also read over this thread http://www.steelsoldiers.com/showthread.php?126598-M923a2-air-question it also mentions the Q2 valve.
Hi Mike. I found this Air Brake Inversion Valve for $91 on Eastern site and can be found in the search typing com5167. is this the Q2 valve? Among other vehicles, it says it fits a M939 and mine's a M934. Seems like a reasonable fix to try if it will fit. Thoughts? Thanks! FrankWith it leaking air both ON and OFF the brake pedal I'm going to bet that there is a leaking pancake or your brake pedal (aka Treadle valve is leaking) of course it could be a combo of all these...
The Q2 valve looks like this on our 939 series trucks. http://www.eriksmilitarysurplus.com/airbrlqfraxl1.html
Have you tried "back filling" the air system with a shop air hose to the emergency gladhand (make sure the wheels are chocked so it can not roll on you!) and go listen by each and every wheel for leaking air (pancakes) if not heard at the wheels then I would start looking at the brake pedal.
The Q2 valve looks like this on our 939 series trucks. http://www.eriksmilitarysurplus.com/airbrlqfraxl1.html
Have you tried "back filling" the air system with a shop air hose to the emergency gladhand (make sure the wheels are chocked so it can not roll on you!) and go listen by each and every wheel for leaking air (pancakes) if not heard at the wheels then I would start looking at the brake pedal.
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If it dumps the air and I mean all air quickly with foot on pedel then q2
Q2 are about 30 bucks on flea bay
Q2 are about 30 bucks on flea bay
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Just search Q2 quick release valve
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I have absolutely no help to give you regarding your problem, but I can help clear up this confusion.
You M934 is specific Model of the "M939 Series". There is no specific "M939" truck - it only denotes a group of similar trucks. The M939 series spans multiple trucks that are built/designed around relatively the same base.
https://en.wikipedia.org/wiki/M939_Truck
Just the same way as you may read about older 5 ton trucks the "M809 Series":
https://en.wikipedia.org/wiki/M809_series_trucks
or the "M39 Series":
https://en.wikipedia.org/wiki/M54_(truck)
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therooster2001
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If you verify it is the Q2, and get one on the Bay, ensure the air vales are the correct size. (3/8"), I got the wrong one first. Easy fix BTW, happened to me. Venting out the stack is the key, and checking the valve and brakes with the truck off, aired up through the rear emergency helped me find it. Get a helper to push the brake, you won't isolate it by yourself. Do not use the truck until you fix it, it's quite dangerous to loose that much air that quick. Just backing it in to my garage caused me to go almost below 40! Good luck, and let us know.
That leaking air without the pedal is still bugging me. That doesn't feel like the Q2., although I knew right away it was the Q2 so any other issue I didn't pay attention to.
That leaking air without the pedal is still bugging me. That doesn't feel like the Q2., although I knew right away it was the Q2 so any other issue I didn't pay attention to.
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plode
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Some of the ones on fleabay don't have the bottom port on the valve threaded either. I know from experience. I ended up tapping it out myself, used it like that for a while, and then swapped it for a non-chinese OEM Q2 just for peace of mind.
My truck still leaks a tiny bit of air out of the stack- I'm 95% sure it's the treadle valve. I've checked all of the brake chambers- it's not them, that I can tell. Problem is, people want $70+ for a treadle valve, and most of them are used- they might have the same issue mine has now.
OK, here's the valve on the truck and here's the LQ-2 Valve I bought off ebay from Global Parts. You can see that it's not identical. If I line up existing hoses on new part, it appears that the truck has one port blocked (the 1/4" port on the new part) and the top port isn't threaded on the new part. Should I search for a new part? Suggestions? Thanks.
therooster2001
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If it were me, I'd get the threaded version, I know someone threaded his, but got the real one after. It seems we all have to get the wrong one first. My lq2 was piped different (check that loop in the picture) and I've seen several configurations out there...
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therooster2001
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I think I actually bought mine from the same seller, they accepted the return.
srodocker
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Wow this may solve my problem! Will let you guys know hopefully within the week
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There are different versions of the same valve, depending on the manufacture. Mostly, MV's are made with "Off the Shelf" brake parts, and are readily available at your local heavy truck store, that are staffed with knowledgeable people with vast air brake experience.
Plumbing matters! Find the valve with the ports going in the proper direction, so you don't have to spend two days re-plumbing your application. The will have parts books, with pictures to help with ID.
Plumbing matters! Find the valve with the ports going in the proper direction, so you don't have to spend two days re-plumbing your application. The will have parts books, with pictures to help with ID.
I just ran into the same problem on my end. Pressing the brake pedal fully causes the primary system to drain to zero within about 45 seconds. I first checked all my service brake diaphragms, all 6, because those also vent to the stack. To check my LQ2 valve I'm going to first disconnect the vent line and then apply the brakes and see if the air no longer escapes from the stack but instead at the front.
therooster2001
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That will work, but for no disconnects, try just having soldier B step on the brake using just shop air, and hang out by the Q2, you'll hear it, if it's that.
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Pulled it out, as suspected it's bad. You can see the rubber ball is split and broken. Its about the consistency of a superball. I found prices ranging from $109 to $26 for a replacement valve but instead decided on a repair kit for $13. Should have it in a few days.
My soldiers B and C don't have thumbs, only dew claws, but fine idea!