Parking brake problem

rip · May 11, 2015, 10:12:10 AM

I took my 85 Prevost out for a ride and when I went to apply the parking brake it would not hold completely.The brakes did apply but when I let up on the brakes the parking brake would not completely hold.
The air gauges show at 120 lbs.and the brakes are adjusted and seem to be working fine.Everything seems to be working except for the parking brake just not holding.Could it be the parking valve or something else I should check

Jon · May 11, 2015, 11:13:56 AM

There is no adjustment to "no air". When you apply the parking brakes all air is dumped and you are relying on your brakes being properly adjusted, the brake shoes not being covered with grease from a leaky hub seal and the springs not being broken. Springs apply the parking brake. Air retracts the springs to release the brakes.

Your coach only has a combo brake on the drive axle which to start with is inadequate. Later coaches had combo brakes on both the tag and drive.

Check to see if you have one or more of the problems listed above.

Lin · May 11, 2015, 11:18:29 AM

I second that. Make sure brakes are properly adjusted and check for any surface problems on the shoes. It is really only the rear brakes that matter for parking, but check them all anyway.

luvrbus · May 11, 2015, 11:30:49 AM

If he has spring brakes probably a broken spring I forgot if a 85 Prevost has springs or DD-3

bevans6 · May 11, 2015, 11:33:20 AM

I was going to ask the same thing - spring brakes or DD-3's. Completely different issues could be the cause, depending... Also double check brake stroke on the drive axle chambers.

Brian

rip · May 11, 2015, 12:49:48 PM

Ok,the left rear duel will not adjust.when I adjust it to lock the brake,nothing.Im not schooled in brakes,so take the tires off and see whats broken.

Jon · May 11, 2015, 01:12:36 PM

While the best learning is from having hands on, just make sure you respect your brakes. An improperly caged spring can hurt you. If you cannot adjust the brakes you may have a new slack adjuster in your future. Or something broke.

eagle19952 · May 11, 2015, 03:05:44 PM

Quote from: rip on May 11, 2015, 12:49:48 PM
Ok,the left rear duel will not adjust.when I adjust it to lock the brake,nothing.Im not schooled in brakes,so take the tires off and see whats broken.

Were I you I would school up before I took the wheel off...

Scott & Heather · May 11, 2015, 04:24:43 PM

I would like to muddy the waters a little if I may please:

My parking brake works just fine. But, I have found myself in a situation before where I was on a very unlevel spot. I had to jack the rear up high to level the coach and dump the air in the bag in the front. I had the rear lifted so high, that the drive axle was barely touching the ground. When heavy rains came, the bottle jacks shifted, the braked drive axle wasn't really doing much because the tires were almost in the air, so the coach rolled back and nearly down a grassy knoll backwards over a group of tent campers. Ok, it only rolled back about 2 feet, but I needed a change of pants when it happened. We could sit and argue my jacking method was flawed, but I mention this scenario simply to ask, is there a way to have all brakes applied? A kit that provides spring braking to all wheels when air is purged? Or a way to just keep air in the system and have the service brakes applied? Something?

bevans6 · May 11, 2015, 04:56:58 PM

Scott - no. There is no way to have all brakes applied with no air pressure in the system. Nor would you want there to be, once you think it through. This is why chocks were invented. Also split firewood, chunks of 4X4, big rocks, spare tires, or your big ugly thing of choice to keep things from rolling downhill.

Brian

rip · May 12, 2015, 05:30:53 AM

Im going to have a shop do the work.I live N/W of Phoenix in Surprise,any suggestions to where I can get the work done.

luvrbus · May 12, 2015, 05:44:47 AM

Divine Transportation 1243 S 7th 602-340-0018 they know buses stay away from Desert West big $$$

Jim Eh. · May 12, 2015, 09:23:21 AM

Quote from: bevans6 on May 11, 2015, 04:56:58 PM
Scott - no. There is no way to have all brakes applied with no air pressure in the system. Nor would you want there to be, once you think it through. This is why chocks were invented. Also split firewood, chunks of 4X4, big rocks, spare tires, or your big ugly thing of choice to keep things from rolling downhill.

Brian

Another way is to have a check person in the drivers seats (with no keys in the ignition) to apply brakes if it falls of the stands or starts rolling.

Cary and Don · May 13, 2015, 03:47:12 PM

We chased this problem in our Eagle spring brakes for ages. It wasn't the brakes. It was an air problem. The park brake valve wasn't dumping the air from the system so the park brake could go on. Our brakes worked with the peddle, but the park brake only applied if all the air was out of the system.

Don and Cary