M931 won't build air.

[Bandit02]

I'm having a serious problem. I was out taking my truck for a boot around town tonight when I noticed that it wasn't building any air after awhile. My gauges were showing the tanks depleting after brake applications and honestly I can't hear the compressor going into the loading stage with the engine running (kinda deaf lol). I noticed a air leak noise underneath but only while the engine is running. I found the air dryer stuck purging, you can feel the pulsations from the compressor just spitting out of this thing. I'll have to wait till tmr when I go to work and get some snap ring pliers so I can remove to inspect it. Anyone have a issue like this? What make is the air dryer? is there a common commercial rebuild kit for these?

THANK JEBUS for the spring brake override and by the time I got home I had 0 PSI in both tanks and limping it in 1st into my driveway.

 

[porkysplace]

Time to service the air dryer.
These threads should help you find the issue .
M923 Not Building Air Pressure
M923 Air Pressure not building past 45 PSI...ANy IDEAS?
M923A2 Air pressure tops @ 65 psi
M923a2 Air Dryer rebuild
M923A2 Air Brake Pressure Issues
M931A2 compressor does not pump?

 

[Bandit02]

I read abunch of these threads. I ended up pushing up on the purge valve and closing it like one of the posts recommended, builds are fine now. Gonna pull it off the purge valve and clean it up tmr. Thanks!

 

[porkysplace]

I read abunch of these threads. I ended up pushing up on the purge valve and closing it like one of the posts recommended, builds are fine now. Gonna pull it off the purge valve and clean it up tmr. Thanks!

I would still do the filters if you have not done them recently , winter is coming .
If you haven't done so yet you can download the TM's free here .
[h=1]TM's for the 939 series trucks[/h]It is highly recommended to read this one
TM9-2320-272-10.pdf
TM9-2320-272-10 Operations manual for the M939 series trucks. Sept 2004
and keep this one handy
LO9-2320-272-12.pdf
LO9-2320-272-12 Lubrication order for the M939 series trucks. June 1990
And good wiring info here
M939_P2P.zip
M939 Series Interactive Systems Guide - Download .zip file, right-click the .zip file and select unzip contents, put the M939 P2P file in your Program Files directory, open the M939 P2P folder, right-click on the runa6w32.exe file, select Send To, select Desktop (create shortcut), go to desktop, right-click on the new shortcut, select properties, select the shortcut tab, make sure the target box shows "C:\Program Files\M939 P2P\runa6w32.exe" c:\Program Files\M939 P2P\nav.a6r, make sure the start in box is empty. This should allow you to double-click the shortcut on your desktop and start the P2P program.

Welcome to Steel Soldiers.

 

[Suprman]

You need to rebuild or replace the air dryer it will just get worse in the cold. The expello valve is rebuilt from inside you have to take the air dryer off and apart. It's much easier to replace.

 

[Bandit02]

Hmmmmm ok. It prolly wouldn't hurt to just rebuild the whole thing.

 

[juanprado]

There are several for sale in the classifieds and epay at a very reasonable price. I rebuilt mine completely (filter,heater,top and bottom kit) and spent close to the same. Maybe $20 cheaper than the units out there. I would have jumped on a complete unit for the price but they were not out yet from GL.

I would say just replace it instead of hassling to rebuild it with the good deals out there now

 

[Bandit02]

I'm going to replace it. With a Bendix AD-9 (with 24v heater) dryer. Simple, parts everywhere, easy to service/rebuild.

 

[Bandit02]

There we go