So I'm new to this group. I have a bmy 5 ton 6x6. My air built to 120 n then I heard a click behind the dash and then it wouldn't build air pressure anymore and air was leaking out of the air dryer. When it first did it I was driving n pulled over n heard the air coming out of the dryer so I rebuilt that thinking it was the problem. Put it back it, built air great, hit 120 n then that was it, pump breaks to drain the air and it won't build up again.
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M923a2 air issue
- Thread starter cmalueg4
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The unloader valve on the air compressor may be sticking or a problem with the governor on the compressor.
The maintenance section for the air system is in this TM
TM9-2320-272-24-1.pdf
TM 9-2320-272-24-1
Section IX. COMPRESSED AIR AND BRAKE SYSTEM MAINTENANCE
Page 842 on the pdf. counter
The maintenance section for the air system is in this TM
TM9-2320-272-24-1.pdf
TM 9-2320-272-24-1
Section IX. COMPRESSED AIR AND BRAKE SYSTEM MAINTENANCE
Page 842 on the pdf. counter
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dilligaf13
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Ditto. If it builds air it's not the compressor. If there's not a leak somewhere in the system it's most likely what porky said. Sometimes its hard to hear leaks with the truck running, so I run air from a compressor to the trucks glad hands to pressurize the system. Then I can check for leaks with the truck off, making it much easier. I had a valve under the step that was stuck and it was leaking air out of the air intake. I never heard it while the truck was running, but once it was off it was obvious...
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The unloader valve is the device mounted on top of the compressor. On my M925A2 it has a 1/4" line coming to it from the governor which is mounted on the firewall. It cannot be accessed without removing the compressor - major pain. Hopefully it's the governor, not the unloader.
dilligaf13
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look at TM 9-2320-272-24-1
and page # 2-197
that's the compressed air supply trouble shooting section
and page # 2-197
that's the compressed air supply trouble shooting section
Ok, so just let it sit for a few hours, started it up, it got to about 70 psi and then opened the valve on the bottom of air dryer, just a few hours ago it got to 120 and then opened the valve on the bottom of air dryer. I just rebuilt the entire air dryer a few days ago thinking that was the problem but I guess it's not.
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Bypass the dryer to see if that is the issue before ripping into the compressor
dilligaf13
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Air dryer is not supposed to pop off at 70 psi. That's no bueno.... Is it sticking open and dumping air out continuously or blowing off excess and resetting?? The air dryer can stick partially open and cause you to slowly bleed air out too
This morning I got to 120psi n then air came out dryer, this afternoon I got to about 70 n air started coming out dryer. Once it starts coming out of dryer it doesn't stop, hense the reason I rebuilt it, but if I let it sit for a few hours it will build pressure one time and then it will continue to leak out of dryer after that til it sits for a few hours.
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I think you have 2 issues, interrelated.
Your expello valve is intermittently sticking in your air dryer. This is preventing you from building air past 70psi.
When the expello valve isn't sticking open and you do reach 120psi and trip the unloader, the unloader is sticking. This causes air to stop building.
Both of these evils are caused by moisture in the system.
Tga
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Moisture and freezing temperatures will create ice crystals that will cause all kinds of issues. Try getting it inside somewhere warm to thaw out and add some air brake system de-ice (or denatured alcohol) to the system and see what happens.
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Like I said....bypass it and you will know immediately if the dryer is the issue. A day wasted with no forward progress.....
Air issue M923A2 6x6
Ok, so the weather finally warmed up and I finally had time to start this beast. Started up, air went to 120 psi, hit the breaks a few times, air built back up, hit the breaks a few more times, heard a click and then it will not build psi and air leaks out the bottom of air dryer, air dryer has been rebuilt. Please help.
Ok, so the weather finally warmed up and I finally had time to start this beast. Started up, air went to 120 psi, hit the breaks a few times, air built back up, hit the breaks a few more times, heard a click and then it will not build psi and air leaks out the bottom of air dryer, air dryer has been rebuilt. Please help.
The pureair dryers are junks.
Member Suprman has a purest air dryers. Contact him at will@ pawnking . Com
Or member fuzzytoaster has a wabco style that needs some modifications to make work
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I have to agree with Wes on the dryers, Suprman has a good deal on them too. I'm about to put one on my 929.
In the meantime, while your waiting on a dryer, try putting some lube in the system. Take the line that goes to the unloader out of the top of the compressor and follow it to the control on the fire wall. That control gets debris built up with condensing water and even fills the control tube sometimes. Take the tube loose on both ends and blow it out. Take the control off and clean it then use a light coat of red grease on the moving surfaces when you reassemble. Count the threads so the adjustment is about the same, that's where pressure is regulated and adjusted. Now put a generous dose of Marvel Mystery Oil (pneumatic tool oil) into the line to lube the parts in that compressor unloader. When the controller sends pressure to the unloader, it pushes a pin to keep the compressor intake valve from coming shut, so it won't build more pressure. That pin/piston gets gunked open. Lube has freed mine up (regular use).... as taking it off is a pain.
In the meantime, while your waiting on a dryer, try putting some lube in the system. Take the line that goes to the unloader out of the top of the compressor and follow it to the control on the fire wall. That control gets debris built up with condensing water and even fills the control tube sometimes. Take the tube loose on both ends and blow it out. Take the control off and clean it then use a light coat of red grease on the moving surfaces when you reassemble. Count the threads so the adjustment is about the same, that's where pressure is regulated and adjusted. Now put a generous dose of Marvel Mystery Oil (pneumatic tool oil) into the line to lube the parts in that compressor unloader. When the controller sends pressure to the unloader, it pushes a pin to keep the compressor intake valve from coming shut, so it won't build more pressure. That pin/piston gets gunked open. Lube has freed mine up (regular use).... as taking it off is a pain.