Air Pressure dropping Park Brake hanging

[Gary8346]

I recently replaced a leaky park brake valve. After doing that I didn't hear any more air leaking and everything worked great for about a month. Then I had a problem with the park brake sticking (not releasing) even though the pressure alarm was off and pressure was about 85 or 90 psi. Waiting a while for the pressure to rise seemed to work but now after releasing the park brake the pressure seemed to drop quickly and the alarm started up again. This happened when going down my fairly steep driveway using several applications of foot brakes. After leveling out at the bottom the engine pushed the pressure high enough and everything seems normal.

I've always had some pressure loss when parked for a while so I probably have a slow leak somewhere. I thought maybe I fixed it when I replaced the park brake valve because pressure held for several days but now its running down slowly again. Another interesting thing is that my air dump switch doesn't seem to work, at least I don't hear any air release like I did before. I haven't fully explored this problem so it could just be my imagination.

I never had a park brake stick before and that seems like it might be a real problem. Is it going to continue to get worse or can I work around it for a while?

[twinboat]

Do you have a push in type knob for the park brake ?

If you do and the knob is hitting the dash, before pushing the valve all the way in, that can cause problems, releasing the park brake.

You shouldn't try to move the MH until you get at least 120 psi on the gauges and hear a purge from the air dryer.