Air Bag # 9

[Larry W]

We stopped for a few minutes and as we started to get back on the road we were greeted with a big air leak. Just as I released the parking brake there was a big air leak. First thought was something with the parking brake. The Aux air gauge was dropping very fast all the way to zero. The problem was the 10 year old bellows in the air ride seat blew out. Add another air bag to the 10 year replacement list.
The important part is that with no aux air the parking brake will not release. If the bellows blows while driving in about 2 minutes you will be parked even if its in the center lane of the interstate.
I plugged the line to the seat and got air back.

[Larry W]

I think I am wrong about the aux air releasing the parking brake but when I was setting on a massive air leak my thought pattern got kinda screwed up.

[Jon Wehrenberg]

Your bus air system is actually three systems, 2 brake systems, a primary and secondary and an auxiliary air system. If all your protection valves are funcioning properly you can have a catastophic air leak on the aux system and you will still retain enough air pressure in the brake systems so they can function, and that includes releasing the parking brake (which is done with the application of air pressure to the emergency brake (parking brake) diaphragm.

Had it been a suspension air bag your bus would have dropped and likely not been driveable at road speeds.