How do you know when brake chambers go bad?

Answer 1

Chock your wheels and release the brakes. Do a walk around. If you hear air escaping and pinpoint it to a chamber, then you have a bad emergency chamber... in which case, you'll probably hear it escaping from the purge valve between the two axles, and you'll need to take a set of pliers or vice grips and pinch off the lines to each chamber to determine which brake chamber is bad.

After that, press the treadle valve (brake pedal)... I use a hood prop rod for this... you can buy them at any auto parts store, although I bought mine from Snap-On (they're also handy for when you have to adjust a clutch). Check again for air leaks... if it's coming from the service chamber in this instance, it's a problem with the service chamber, and you should be able to pinpoint the specific brake chamber by sound.