M923 A2 air brake issues

[Jermey]

Looking for some help.

Ive had the truck for a few months now drove it over 6hrs home no issues truck is in great shape everything is funcitional including the CTIS. Last week I started having issues out of my air brakes when you spet on the brake it releases pressure like it should but then continues to bypass air out of the snorkel. Ive changed all 3 check valves under the drivers step, all new pancakes in the service brakes whick all but 1 where the original rockwell pancakes. The truck builds and holds air pressure just fine until you hit the brakes. I know it cant be on the parking brake side either because they function as they should. The air brake foot valve looks like there has been a leak there before but doesnt sound or seem like it is now. Any help please.

 

[simp5782]

Which tank is losing air? Primary, secondary or both?


Go under the truck. Drivers side inner frame rail. Right behind the air tube there is a T block with a bunch of lines going into it. Sometimes there is 5 sometimes there is 8.

The lines will be white. White = vent. This is the brake vent to the air stack.

Remove one line at a time and see which one is leaking the air.

Ones coming from the rear indicate an axle in the rear.

Ones from the front can be a front Q2 valve or a brake pedal valve.
**if the ones from the front are leaking, next step would be to remove the vent line from the front Q2 valve In front of the front axle and see if it dumps air continuously. IF NO, go to the firewall in the engine bay, remove the bottom line from the brake pedal valve on the firewall, see If it vents continuously.

There are some smaller lines, one is for the parking brake linear valve, the other is for the transfer case and one for the transmission.

Just figure out which one is puking the air and we can go which direction it is.

 

[Jermey]

Which tank is losing air? Primary, secondary or both?


Go under the truck. Drivers side inner frame rail. Right behind the air tube there is a T block with a bunch of lines going into it. Sometimes there is 5 sometimes there is 8.

The lines will be white. White = vent. This is the brake vent to the air stack.

Remove one line at a time and see which one is leaking the air.

Ones coming from the rear indicate an axle in the rear.

Ones from the front can be a front Q2 valve or a brake pedal valve.
**if the ones from the front are leaking, next step would be to remove the vent line from the front Q2 valve In front of the front axle and see if it dumps air continuously. IF NO, go to the firewall in the engine bay, remove the bottom line from the brake pedal valve on the firewall, see If it vents continuously.

There are some smaller lines, one is for the parking brake linear valve, the other is for the transfer case and one for the transmission.

Just figure out which one is puking the air and we can go which direction it is.

I am on it today thank you for all the help!

 

[Nasher]

Make sure the spring brake over ride on the right side of the dash is pulled out.