m939 air system check valve

[M35A2-AZ]

Sounds like you need to adjust your Governor down a little, it is on the firewall on the motor side.
The St-3 check valve is at the back end end of the wet tank, the PPV is on the front end of the wet tank.

 

[R Racing]

I believe I have found my air problem that has drove me nuts !! the flex line between the engine and the frame had a good size hole under the sheath so you couldn't see it . I was working on the unloader valve on the compressor and washed all the parts down with wd40 . And noticed a mist by the starter? it was the wd40 misting out under the sheath !! It would only leak when the engine was running. with the engine off no leaks. The check valve kept the air from leaking when the engine was off! and when the engine was running it was to loud to hear the leak!

 

[5ton toys]

It could also be a leak between your compressor and your Governor on firewall

 

[R Racing]

I had that line off and checked it in my shop.also used soapy water to check it installed. I checked all the lines under the hood with soapy water.

 

[R Racing]

Went to my local hose maker today and $20.00 later I now have a m923 a1 that has 120 psi of air in about 4 1/2 minutes while idling. No more 20 min of 1500 rpm to get it pumped up

 

[dawico]

Very nice and a pretty cheap fix. Glad you found the problem.

 

[LiqTenEXp]

I am looking to try to find the part number of that flex hose you are talking about, mine is also leaking. I can't seem to locate it in the TM.

I can only find M939A2 air hose replacement sections, I am looking for a straight M923 version of it and not the M923A2, are they different in that aspect?

 

[LiqTenEXp]

nm, its a make item. Not something I can buy. What kind of "hose place" did you go to that made your hose up?

 

[R Racing]

Went to Henrys Engineering in Prince Fredrick Md. Took my old 1 with me and they made me a stainless braided Teflon lined hose. They had to give me 2 pipe adapters with it. And I had to use the 2 old fittings to reattach it to the original copper pipe. I'm so glad I have it fixed. It about wore me out after replacing the check valves. The air governer. And taking apart the unloader valve.

 

[R Racing]

nm, its a make item. Not something I can buy. What kind of "hose place" did you go to that made your hose up?

Any hose place that makes up hydraulic hoses and fuel lines can make 1 up for you. Also places that repair hydraulic cylinders should have all the fittings to make it as well

 

[datadawg]

I started my 923a2 for the first time in around 4 months. It's been sitting outside in Pennsylvania all winter. It fired up in 50 degree weather immediately, which was a pleasant surprise. But to my dismay, it was not building pressure, both primary and secondary tanks were close to zero.

I have read tons of posts and don't really have a game plan, all the suggestions to various problems are starting to get commingled in my mind. I'm thinking I have to get a diagram and just try following diagnostic steps in order. Problem is, I can't find the right section in TM. I have TM 9-2320-272-24P-1, which is 964 pages. I also have the TM 9-2320-272-10, which is 452 pages. My eyes are already blurry, does anyone know which section deals with diagnosing no pressure issues?

 

[R Racing]

I'd check the easy stuff first like a stuck air govonor . Or stuck unloaded valve first. Also any air leaks like a tank drain left open or a hose that may have had water in it and froze over the winter and cracked.

 

[dawico]

I started my 923a2 for the first time in around 4 months. It's been sitting outside in Pennsylvania all winter. It fired up in 50 degree weather immediately, which was a pleasant surprise. But to my dismay, it was not building pressure, both primary and secondary tanks were close to zero.

I have read tons of posts and don't really have a game plan, all the suggestions to various problems are starting to get commingled in my mind. I'm thinking I have to get a diagram and just try following diagnostic steps in order. Problem is, I can't find the right section in TM. I have TM 9-2320-272-24P-1, which is 964 pages. I also have the TM 9-2320-272-10, which is 452 pages. My eyes are already blurry, does anyone know which section deals with diagnosing no pressure issues?

I would start by pulling the outlet hose apart coming off the compressor. If it is hot while the truck is running then don't bother. The compressor is pumping if the hose is hot.

If so, start looking for leaks. Are the tank drains closed? Glad hands? Air dryer purge?

If it isn't pumping then it is probably a stuck unloader. You can check the hose going from the governor to the unloader but I am not sure how. I haven't had to do that yet.

The TM 24P-1 is the parts TM. Download the 24 TM (no P, P=parts). There is another diagnosis TM also, 34 maybe?

If you get the right TM it is pretty simple to diagnose, but it generally doesn't tell you how to fix much, just replace it. That is where we come in.

Good luck.

 

[Artisan]

Make a GladHand x Your-shop-air-compressor adaptor, chock
the wheels and pump it up and listen for the leak. Connect to the
DS front Gladhand.

Are all your drain down valves closed?
Are all your tank valves OPEN?

It is something silly I bet.

 

[gottaluvit]

I started my 923a2 for the first time in around 4 months. It's been sitting outside in Pennsylvania all winter. It fired up in 50 degree weather immediately, which was a pleasant surprise. But to my dismay, it was not building pressure, both primary and secondary tanks were close to zero.

I have read tons of posts and don't really have a game plan, all the suggestions to various problems are starting to get commingled in my mind. I'm thinking I have to get a diagram and just try following diagnostic steps in order. Problem is, I can't find the right section in TM. I have TM 9-2320-272-24P-1, which is 964 pages. I also have the TM 9-2320-272-10, which is 452 pages. My eyes are already blurry, does anyone know which section deals with diagnosing no pressure issues?

So, what actually was the issue?