no air pressure M931A2

[clews1975]

I have a M931A2 which I was driving when i heard a squealing noise which sounded like brakes came from what seemed to be under the truck. I stopped the truck only to realize that the noise didn't stop. As I scanned the gauges I noticed that the air pressure was low, but keeping steady. Upon arriving home I shut the truck down and walked away. In the am when I started the truck I noticed air pressure was not building.... above 10 lbs in primary and 15 lbs in secondary. I hitched up my M923A2 to the air system of the M931 to charge. When I hitched it to the drivers rear gladhand the air started to come out intake and would not charge system. I tried right rear, and it charged up truck as normal, and holds air. Is this normal?
I have read the tm's over and over, and many post about this kind of thing with these trucks. One of the tm's suggests a valve under drivers step. Any ideas or suggestions would be greatly appreciated.

 

[clews1975]

Did I post this in the wrong place?

 

[patracy]

Did I post this in the wrong place?

Yes, you did. Moved to the 5 ton forum.

 

[patracy]

And by intake, I assume you mean the engine air intake stack? That's where the vent lines for the air system and various drivetrain vents lead to.

 

[ichudov]

I had a similar problem. It was caused by the expello valve stuck in the air dryer and the aair from the compressor was coming out of that valve. By advice of a member here, I pushed the valve up and it fixed it.

 

[clews1975]

M931A2 Not building air pressure

I have a M931A2 which I was driving when i heard a squealing noise which sounded like brakes came from what seemed to be under the truck. I stopped the truck only to realize that the noise didn't stop. As I scanned the gauges I noticed that the air pressure was low, but keeping steady. Upon arriving home I shut the truck down and walked away. In the am when I started the truck I noticed air pressure was not building.... above 10 lbs in primary and 15 lbs in secondary. I hitched up my M923A2 to the air system of the M931 to charge. When I hitched it to the drivers rear gladhand the air started to come out intake and would not charge system. I tried right rear, and it charged up truck as normal, and holds air. Is this normal?
I have read the tm's over and over, and many post about this kind of thing with these trucks. One of the tm's suggests a valve under drivers step. Any ideas or suggestions would be greatly appreciated.

 

[clews1975]

Also Can someone tell me where the isolation valves are for primary and secondary air?

 

[doghead]

Do NOT start a new thread on the same topic as your last thread. Continue one thread.

 

[dmetalmiki]

When charging the (an) air system you should use the Emergeancy INPUT. this is on the front of vehicles. And is coloured RED. Shoving air into (unkown (or incorrect)) Outputs is not recomended. Try to read and understand the schematic about your trucks air brake circuits. Look for Check (one way) valves. There are also important relief (pressure control) Valves that maintain and control air pressure. Try to get some idea of how the system functions and then locate the precise point at which the air (loss) is emmitting from. You seem to have a general idea of that allready. So verify and then go back to the books and confirm the guilty component. Don't get flumaxed (frustrated) you will eventually get there ( and get the hang of posting!) good luck keep us informed of your prognosis eventual "fix" and result.