Parking brake

Check all chamber and make sure quick release valve is doing its job also check slack adjusters and make sure no brakes are out of adjustment

 

I’m having this same issue. I pull the brakes and it rolls, it nearly got me last week. Any recalls or info on this?

 

New brake chambers take around 80 PSI to compress the spring and release the park brake after some use they need about 60 PSI to release them.
The park brake springs in the chambers break and then there is no park brake
on that wheel. Over time the springs can weaken from years of being compressed and still look good and not hold.

Take the plastic plug out and look inside the chamber with a light. You should not
see the end of a broken spring and the slot for the release bolt should be close enough
to the center that you could put a release bolt in if you needed to. While you are under
there give each chamber a kick with your boot. If it sounds like you just kicked a coffee
can full of marbles then you have a broken spring in that chamber.

 

I’d replace both chambers and maybe check to make sure the air is getting fully dumped from the chamber when you pull the park brake button
It could be an issue with one of the dump valves or the yellow valve not totally cutting off the air .
Easy way to check this is park on a slope, turn off the engine and use the foot brake to pump down all the air , pressing and releasing it until the air is totally exhausted from the tanks and lines , but you need to do this in a safe way,
Easy to do if your truck has a manual trans , but if it’s a automatic you need a way to stop the truck if it starts rolling .

on my rigs I always added park brake chambers to the other axle as well so all four wheels locked up .