Motorhome Air Parking Brake Not Releasing

[rsalhus]

Our MH is a 2001 Rexhall Vision DP with a 260 HP Cummins ISB engine. It has hydraulic brakes with electric assist, and an air compressor and tank which is used for the parking brake and the four airbags. There are no air pressure gauges.

A few days ago, after driving the MH a ways, I stopped for a minute and set the parking brake. Later when I released the parking brake, it acted like the parking brake was still partially set, it was very hard to drive away and the air compressor came on and stayed on like there is an air leak somewhere. However, when the parking brake is set, the airbags do fill and the compressor shuts off normally. It's only when releasing the parking brake that the compressor comes back on and stays on (meaning it never gets to its operating pressure) and the parking brake acts like it didn't get released. Releasing the parking brake doesn't sound as loud as before, also indicating the pressure isn't as high as it should be.

I don't think I want to drive it to the shop like this, even if I can, so I'm thinking I want to manually disconnect the parking brake first but I don't know how that's done and I don't have any manuals showing how it's done.

I called the Spartan Customer Service Center and got them to send me the attached PDF diagram of the transmission-mounted parking brake, but I still can't figure out how to manually release the brake. Does anyone have any ideas?

[eddiepotts]

I would suggest pulling the #10 pin and manually moving the arm to the release position. Just know this is not your only break that’s working.

[rsalhus]

Quote:

Originally Posted by eddiepotts Just know this is not your only break that’s working.

What's the other one(s)?

[RVDude]

JMHO - Get some heavy duty wheel chocks before pulling the #10 pins. You'll need the chocks as your new parking brake with those pins out. You'll also want to carry a second person to apply those wheel chocks every time you park as you'll need to hold the service brake until that second person applies the new parking chocks as you won't have time to do so and chocks likely won't stop an already rolling vehicle.

[EngineerMike]

rsalhus-
1) does your parking brake light on the dash (I assume you have one) go out when you release? There should be a pressure switch to activate the light, and if it goes out the switch thinks your brake released. These switches can go bad.
2) Here is a link to a thread on Alpine parking brake fixits. The diaphragm actuator should be available if you have the original off the rig to match it. It would help to know the effective throw distance of the diaphragm's actuator rod if you need to do a match when ordering; that should be available in Haldex's (or whoever's) spec sheets for the actuators. Check out the issue w/the leaking pressure sensor that operates the dash light. The thread also talks about temp rigging of the air brake by removing the pin.
3) Worst case would be if now-available units have some different bolt pattern to the mounting flange, as that would require removal of the mount & some custom drilling or other fab work.

[rsalhus]

Quote:

Originally Posted by EngineerMike rsalhus- 1) does your parking brake light on the dash (I assume you have one) go out when you release? There should be a pressure switch to activate the light, and if it goes out the switch thinks your brake released. These switches can go bad.

No, I don't have a parking brake light issue. That's not to say that the sending unit (pressure switch) is not the cause of the leak, however. But the parking brake lights (part of the group of idiot lights) seems to be working fine.

Thanks for the link. Nice to see I'm not the only one with parking brake problems. Do all Alpines have transmission-mounted parking brakes or just the ones with hydraulic brakes? Just curious.

[rsalhus]

Here's an update on this problem. I got a PDF file of this parking brake from Spartan and am posting it here. I found out the cause of my problem is air leaking from the spring brake chamber diaphragm. I disabled the parking brake by removing the pin (10) as shown in the diagram. Now I need to replace either the diaphragm (wish it were that simple) or the whole chamber brake assembly. I'm not having any luck finding this part anywhere except from Spartan. I believe ilt's made by Haldex/Midland.

[GaryKD]

Hi rsalhus,
Thanks for the PDF file. It has been added to my library.