Air brake problems

[Firefly]

I have a 94 Bluebird rear engine with airbrakes. I hadn't run it for some time and just started it up and let it idle. So far, so good. Then I checked the transmission, or tried to, and the air brake valve would not go in and stay in. It really didn't stay in at all. but pushed out. I managed to hold it in long enough to check the tranny, and that was ok too. Next I tried to break the brakes loose and they did. Except for one moment, the button behaved as if it wasn't locking the brakes at all, and I could move back and forth in the space I had. Now the bus is pretty much held in place by the divots in the soft ground they had made for themselves. Whew!
A lot of background to ask if it is the air valve I need to replace or is it something else I haven't thought of?

[Eclipse436]

Did you drain your air tanks yet? Water in the lines can cause air brakes to fail. Also check your pad thickness and slack adjusters

[Deezl Smoke]

Really need to know what air pressure gauge said when you tried to push in the valve button. Low air pressure will not allow release. Low air pressure can be the compressor governor or any other stuck open component including the air dryer purge. Also a leaky air brake can at the axle can cause all kinds of odd actions in the system. But I would like to know what the gauge said first.

[Firefly]

Originally Posted by Deezl Smoke

Really need to know what air pressure gauge said when you tried to push in the valve button. Low air pressure will not allow release. Low air pressure can be the compressor governor or any other stuck open component including the air dryer purge. Also a leaky air brake can at the axle can cause all kinds of odd actions in the system. But I would like to know what the gauge said first.

Both emergency and service pressures were up to normal (110-120 psi).
I have not drained the tanks yet as it was getting dark.

[Deezl Smoke]

Ok, now you may have air passing through a diaphragm in one of the brake pots. Can you hear air passing through the valve behind the button when you hold it in?

[Firefly]

Originally Posted by Deezl Smoke

Ok, now you may have air passing through a diaphragm in one of the brake pots. Can you hear air passing through the valve behind the button when you hold it in?

I just had it running again and I don't hear air flowing in anyway, either behind the dash or through the brakes when running. I did drain the tanks and they had very little, if any moisture. The brake button will still not stay in, but the brakes are fully released and it will move back and forth, and the brakes act normally. It builds up to 120 psi, and stays between there and maybe 105 lbs. The compressor does bleed off excess air in the normal manner, and when the brakes are pressed and released they also give off the normal air brake "whoosh".

[Firefly]

Brain surgery has had me off the project for a while, but all of the particulars of this problem are the same. Started it this week, same ol' problems. I'd like to know a hint of the problem as me fitting under the dash to replace the valve ain't as easy as it once was. I did try spraying the valve with WD 40 to no avail.

[brokedown]

Hey bud, glad to hear you've gotten past tough problems and can worry about brakes again.

My 1997 TC2000FE was being flaky about releasing the air brakes, I'd have to hold it in for 10 seconds or so before it'd actually take. Then a couple weeks ago I was doing some air leak testing and found the spring valve decide to stick open and just dump air out. That had just started right then and was a brand new problem, but I went right to ebay and found a NOS replacement part for about $50 shipped. Now my parking brake releases normally and no more dumping air out.

My part was a Bendix SR-1 which is pretty common but if you examine yours it should have a part number stamped into the metal.