Auto Park Brake 2001 Workhorse

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Henry J Fate

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Jun 14, 2018
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Hello everyone. Hope all is well

2001 Winnebago brave 32 ft class A  workhorse chassis with the auto park brake.

Yesterday I pulled up to a camping parking spot and engaged the parking brake while I reviewed the area to safely back the coach in. After a minute or so I released the brake, pulled slightly forward then put the transmission in reverse and began to back the coach into the space. I was half into the space and half out when I heard a motor running so I put the coach into neutral to get a better idea of what I was hearing. It turned out to be the auto brake pump motor. Still in neutral I set the park brake then released it. After fully releasing the motor came back on about 2 or 3 seconds after initially shutting off. The brake appeared to be fully released so I continued backing in. The motor popped on and off a couple of times during the 5 minute parking sequence but eventually stayed off. This was the first time any abnormality of the parking brake was realized. I checked the reservoir it was fine and I found no evidence of a leak however today I will crawl underneath to examine the hydraulic line that services the park brake. Last night I reviewed the park brake system and found that the pump assembly appears to be turning the pump on/off based on it being energized turning on at about 1200psi and off about 1400psi. When pressure is in this range the park brake is released. To engage the park brake designers use a solenoid valve that is energized by either placing the transmission into park or pulling the actuator switch on the dash. Once the solenoid is actuated it releases the 1200-1400psi in the line and returns the hydraulic fluid back to the reservoir.

I guess it could be several failures but I am curios to know if any members have had a similar occurrence and what remedy was used. Also I reviewed a modification to the parking brake system which basically requires a 12 volt activating source to energize the brake in addition to releasing it. The factory design energizes the solenoid to release the brake and applies the brake when the 12volts is switched off.

Thanks everyone

My new plumbing layout has worked as I designed it to. The adavents have become inactive now that the tank vent is always available to take in air when dumping and release air when waste water is filling the tank

Henry
 
I'm not sure if anything I'm about to post will help, but I figure the more information you have the better.

Here is a link on how one person eliminated the the hydraulic side of the system. Be forewarned this is not a decision to be made lightly. http://www.wolfswords.com/motorhome/auto_parking_brake/auto_parking_brake.html
I did this on my '97 Fleetwood Bounder, and it worked very well, and it was real easy due to the fact that the coach had the foot actuated brake pedal.

Here is another source of info just for the AutoPark system.
http://www.oemys-performance.com/j71autopark.htm

Again hope this helps.

Corky



 
Crawled under the coach today and found no evidence of a leak which is supported by a full reservoir. Everything looks good. I turned the ignition on and the brake is releasing but the motor continues to run and it sounds like it is having a hard time probably and hopefully from a bad pump switch. I researched Corky's links and found that this switch commonly fails however there are still other possibilities that could be causing the problem. I did move ahead and ordered a new pump switch. $79.99 pick up in the morning. I will install that and see if it solves the problem. There are 3 other possibilities that I can think of. The release valve could be passing pressure when closed, bad pump or a bad back flow preventer. There isn't really anything else unless an undetected leak has begun.

It's funny how things happen. The failure occurred just as we were parking for 8 days and had just driven 650 miles over the previous 3 days. One of the results of the pump not shutting down is eventual leaking from the excess pressure. I guess it could have possibly gone unnoticed long enough while driving and have created more problems and possibly been on the side of the road. I just hope it is the switch.

Thank you very much Corky. The information you sent was an enormous help.

I will update as repairs progress.

Henry
 
Just so you are aware for next time the rotten green switch is available on Amazon for much less $$$ (half)  https://smile.amazon.com/ACDelco-15961566-Original-Equipment-Parking/dp/B0010G9WMA/

Also Brazel / Ultra RV products has a more pricey lifetime guarantee replacement set of pressure switches,  https://www.ultrarvproducts.com/US21-UltraStop-P32-Park-Brake-Pressure-Switch-Upgrade-Kit
 
Picked up the pump switch this morning from NAPA $79.99. I guess this price was a little high according to Isaac's research but all is good. I needed it quickly. I wasn't sure this was the problem. We leave our location on Sunday so it was important to get the part asap in case it turned out not to be the switch.

I am happy to report that I installed the new green switch this morning and experienced positive results. I cycled the park brake hydraulics about a dozen times without a problem. The system appears to be working as designed.

Thanks for the info Isaac. If I wasn't out on the road I certainly would have taken your advice on a more economical approach. This morning I am quite happy it was the switch and all is complete. Now I can get back to my planned schedule.

Thanks again to Corky and Isaac

Henry
 

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