Air brake (parking) valve repair questions

[TacMac2012]

If anyone has looked, the valves under these trucks are a pain to get to from the bottom, and the exhausts are all tied together. When I press the park brake valve sometimes it will release the brakes, but then may pop back up with the brakes still being released (yea that's not safe!).

Any ideas where to start? I am honestly thinking about removing the bed just to make access to everything easier.

 

[simp5782]

If anyone has looked, the valves under these trucks are a pain to get to from the bottom, and the exhausts are all tied together. When I press the park brake valve sometimes it will release the brakes, but then may pop back up with the brakes still being released (yea that's not safe!).

Any ideas where to start? I am honestly thinking about removing the bed just to make access to everything easier.

You need to test air pressure to the valve directly make sure it's not floating around 60 psi which is the pop pressure . It should be over 100 psi supply. If pressure on supply is good and there is no massive loss when pushed in or applying brakes that would cause the tank for that supply to run out of air then replace the valve. Leave the gauge hooked up for brake drop test

You need a 3 way pushlock T for your air line size. 3 or 4ft of nylon/plastic dot hose, standard truck air gauge with fitting you will cut the supply line in a good place of access for you to tap in

And a 2 way connection union to hook the line you cut back to itself when done testing