Leaking air when braking

[dshetron1]

--- In WanderlodgeForum@yahoogroups.com, "Kevin McKeown"
wrote:
>
> Coming home from the weekend in my BB last night, I was in some heavy
> stop and go traffic, and I kept hearing some hissing of air whenever I
> applied the brakes, and watched my air pressure begin to go down
> noticibly when the brakes were activated. When I let off the brakes,
> the hissing stopped, and the air began to build up normally. The air
> sounded like it was somewhere street side, toward the middle or front
> part of the bus. It was like an air line to a wheel came off, but the
> brakes worked fine. The air got down to around 70 PSI, and after about
> 5 minutes of this 0-10mph using the brakes only when necessary (big gap
> to the car ahead of me) everything return to normal...no more hissing
> on braking, pressure built up to around 125-130 PSI and purged from the
> dryer, etc, and the rest of the 60 or so miles home were uneventful.
> Don't we love these intermittent problems....
>
> Something stuck, and now OK? Something to look for/replace? Since it
> is OK now, where should I begin to look? I was afraid of getting stuck
> on the So Cal Fwy's when the air got down to 30 PSI and my brake button
> popped...ideas??
>
> Kevin McKeown
> Yorba Linda, CA
> 1986 38' PT
>
Probably a blown diaphragm on a brake chamber.