Need Guidance, M923 loses air zero leaks found

[911BRIS]

Having a **** of a time finding source of lost air from m923, not bleeding back to compressor, and no external leaks found. It is a fast leak draining both tanks. not sure if anyone ran into this before?

thanks for reading

 

[sandcobra164]

Is it leaking with the parking brake applied (lever raised) or just when the parking brake is released (lever down)? The reason I ask is a large leak can sometimes be a parking brake diaphragm that is cracked or ruptured. If that's the case, it should only do so when the lever is down.

 

[911BRIS]

Is it leaking with the parking brake applied (lever raised) or just when the parking brake is released (lever down)? The reason I ask is a large leak can sometimes be a parking brake diaphragm that is cracked or ruptured. If that's the case, it should only do so when the lever is down.

Thank you, Tryed both ways, brakes applied and released. Equal loss in a half hour to 0psi.

 

[sandcobra164]

It doesn't take much of a leak to drop to zero psi in 30 minutes time. When my truck was doing that the issue was a very minor leak at the rear glad hand valve on the emergency side. Mine now sits about an hour before dropping to zero, I need to replace my overpressure protection valve as that is my issue now.

 

[jetman10]

I have a '67 deuce and mine goes to "0" after abut 3 hours . I've checked everything I can find and no luck . I've added power steering assist, air horn, they aren't leaking . I almost think it's back at the tanks . Hard to get to with the body mounted . How can you check that it's not going back to the compressor ? Thanks .

 

[NDT]

Get some Mr Bubble mixed with water and a paint brush and go over everything. This was how we found leaks at the second largest air conditioning manufacturer in the world. I kid you not.

 

[162tcat]

Having a **** of a time finding source of lost air from m923, not bleeding back to compressor, and no external leaks found. It is a fast leak draining both tanks. not sure if anyone ran into this before?

thanks for reading

If it's not causing any driving issues and not getting worse, don't sweat it. I've never driven a truck (Military or civi) that didn't lose most or all of its air in 4 hours or less.


Sent from my iPhone using Tapatalk

 

[patracy]

Get some Mr Bubble mixed with water and a paint brush and go over everything. This was how we found leaks at the second largest air conditioning manufacturer in the world. I kid you not.

Soapy water is wonderful for finding air leaks. I've used this since high school when they taught us this as a safety check with the oxygen and acetylene regulators.

 

[74M35A2]

Check all 4 glad hands, their valves, and covers. I had same issue as you mentioned, twice, and that was the cause both times. Once was while driving, kind of scary but got to safety and found problem. Fixed in 10 seconds. They can and do get bumped around, played with while you are not looking, etc.

 

[911BRIS]

thankyou for the reply's, tryed the soap and water trick several days no avail. unfortunately it is a brush fire truck that is left inside. I know myself the nature of the beast and it is not a high end firetruck I personally do not expect it to hold air for an hour but the town does so I am stuck with it until I exhaust my resources.

note, for the compressor leak question. you check checkvalve bleed back to the compressor head by pulling the charge line off the compressor and seeing if it leaks there.

 

[WillWagner]

Air it up from another source and lay under it. If it leaks down to zero in 30 min, it should be fairly easy to hear/find with no outside noise.

 

[911BRIS]

INSTALLED SHUT OFF VALVED REAR PASSENGER SIDE TANK, ISOLATED SYSTEM LEAK. Ordered m923 manual. Found leaking check valve lower tank passenger side. Will replace and update!

 

[911BRIS]

okay replaced three check valves all were full of rust and leaking. Two on passenger side (there are three tanks on passenger side, third having no check valve). one check valve on drivers side.
secondary tank holds now, primary leaks still but not as fast...

 

[simp5782]

Then your leak is on your wet tank. so maybe it is a emergency glad hand is left open or cracked atleast

 

[911BRIS]

okay, apparently the brake relay valve at the forward/rear differential decided it was time to leak out of its exhaust port.

 

[simp5782]

okay, apparently the brake relay valve at the forward differential decided it was time to leak out of its exhaust port.

misread

 

[911BRIS]

Here's the valve looks like a 24 volt haldex

looks like a member on here has a good deal for them for $120 have contacted. great forum here.

 

[911BRIS]

took valve apart cleaned rust and lubed with dielectric grease. no longer leaking. small loss primary tank still will continue to investigate. hopefully this give guidance to others in search.

 

[74M35A2]

Just get the 2 cylinder air compressor.

 

[911BRIS]

I WAS ACTUALLY WONDERING IF THERE IS A UPGRADE FOR THE ENGINE MOUNTED COMPRESSOR, I MOUNTED AN ON-BOARD AUX COMPRESSOR FOR 110 POWER.

Just get the 2 cylinder air compressor.

well I installed a shut off at primary tank, crimped off hoses until the gauge stopped dropping from the remaining pressure in the lines, looks like final repair will be the foot valve, ordered overnight from Memphis equipment, will see.

appears truck had a ton of air system issues after all, likely stemmed from lack of air tank/water draining (rust in system). high condensation from overrunning the compressors due to leaks.