W24 Park Brake Failure

[av42]

Tuesday while leaving Las Vegas on interstate running about 62mph the coach felt like engine quit and coach started slowing. when I looked at dash the brake failure light(also indicates park brake operation) and auto park light were on and there was a noticable brake drag.

I was in middle lane and and was able to get to right but no where to pull off except exit ramp about 300 yrds ahead. As I got to ramp the auto park lights would flash off and on, each time the brake seemed grab hard. By the time I got to top of ramp and was able to safely stop, ther was brake burning smell. I put coach in park applied the park brake lever and shut off engine, but the park brake did not hold, had to block wheels.

After 20 min, consulting with Coachnet tech, I started engine and park brake lights were out, but park brake would not hold. Coachnet contacted Workhorse dealer they recommended (Fairway Chev) but they could not take coach until today. I drove the coach there and it drove normal no noticable brake drag and auto park lights did not come on.

After checking coach they told me rear brake pads look burnt almost melted,must be replaced and auto park brake drum looks as if it was overheated and would probally needs lining to be replaced, but they have no clue to why park brake came on and don't know what to look for.

Service writer says they are waiting on a return call from Workhorse for tech help and where to look.

Can anyone on forum offer any advise on what to look for as cause?

[DriVer]

Quote:

Originally Posted by av42 Can anyone on forum offer any advise on what to look for as cause?

av42, You have a J72 auto apply brake system. I can't say what would have caused your AAPB to come on however what you are describing is a rare event for a J72 and I would not be too surprised that the techs are scratching their head. I'd wait for the RSM to call back with what he has to offer about this issue.

[Mr JP]

av42, I also have a 2005 w-24 chassis and about a year ago I experienced a rear brake problem. The rear ABS sensors were found to be bad (1 was melted !!) The tech could not find a real reason for the failure. I had them flush the brake fluid and they replaced the two bad sensors. I did not have the auto park problem and sorry to hear about that. Fairway has been around in Vegas a long time. Good luck and let us know what they found.

[av42]

The Wh repair center released the coach last night, stating they could not find a problem with the auto park, and that with the tests they performed including checking for failure codes they could not recreate the evvent that occured with the sudden locking of the brake. They said that they finally got a call back from Workhorse tech, but they could not offer any suggestions other than what they had already done. They said the only problem they could find on the coach is it needs rear brakes, but it will take a week to get the pads.

Although service said their tech says park brake holding normal, i don't think it is. If I put coach in drive and leave park brake lever applied and apply power the coach will move. This was not the case before the event with the systen occurred.

I am going to have the workhorse center in my next destination check coach, I used them last year and they are very good.

[oemtech]

Just for grins try Oldusedbear and see if he can shed any light on it. He is the J71 expert and may have some info on the J72 that the techs don't.

[DriVer]

Quote:

Originally Posted by oemtech Just for grins try Oldusedbear and see if he can shed any light on it. He is the J71 expert and may have some info on the J72 that the techs don't.

OUB has recently posted that he is NOT a J72 person. I would not expect too much from the Bear in this regard.

[av42]

When we were preparing to leave campground coach would not start, total lack of 12v power to dash and starter. Checked battery full charge. Furthur checking found no power coming out of 12v batt cut off switch. when I tried to turn switch knob came off and whole assembly fell apart.

It appears that a storage bin in the compartment where the switch is located may have fell against it and cracked the housing.

If this switch was failing and caused a momentary loss of 12v, is it possible that caused the engine to momentary lose power and shut off like I indicated in my initial post?

Acording to the workhorse owners manual if the engine shuts off it can cause the auto park come on. According to the Wh. dealer they could find no problem and they had checked for engine codes.

If there was a power failure would that show up on codes?

I changed the switch (bought at a local marine store) and drove over 300 miles with no other problem other than auto park no longer holds properly.

[millsrv]

I think that you have found the problem. If the battery became disconnected while driving there may have been open circuit voltage from the alternator. Based on my experience, (mechanic for 35 years) this condition can cause all kinds of strange things to happen.
As far as codes setting, I would certainly check, record and clear them if they exist.
I know a few things about the J72 Auto Park System, having one on my coach.
The pump assembly mounted on the bulkhead next to the radiator must maintain around 1500 psi to the brake drum assembly mounted on the back of the transmission. The pressure holds the brake off. There is a computer that controls this system. If the pressure drops the pump will run to restore it.
If the system voltage went high or low, the system may have responded in the way you experienced.
Good Luck to you.