Issue with Infamous P30/P32 Auto Park Brake

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GemiNiveK

Well-known member
Joined
Jun 20, 2015
Posts
120
Location
St. Louis
Get ready for some good reading!  ;D

Let me start by saying that I feel I have a good knowledge of how the J71 Auto Park Brake works on my Workhorse P32 chassis (2000 Winnebago Brave 32T).  When I purchased this coach about two weeks ago, the original owner knew that there was a mysterious delay in the application of the Auto Park Brake once the coach had been driven long enough to reach normal operating temperatures.  Therefore, chocks were always used by him and I planned to do the same.

I drove it about 100 miles (80-90 of which were highway) from the previous owner's home to my home and all was well.  The Auto Park Light was off when it was supposed to be off.  However, when I parked the coach (i.e. put it into Park with the gear shift as well as pulled the yellow Park Brake knob on the dash) the Auto Park Light did not illuminate nor did the Auto Park Brake engage.  So I hopped out and chocked some wheels and went on my way.  The next time I drove the coach (the next day) when I fired it up the Auto Park Light was illuminated and the Auto Park Brake was indeed engaged.  When I pushed in the yellow dash knob then moved the shift lever into D, I heard the Auto Park Brake hydraulic pump kick in and within five seconds the Auto Park Light went out.

I drove the coach across town to a friend's location, perhaps 2 miles.  I did not shut off the engine when I arrived.  When I shifted into Park the Auto Park Light illuminated and the Auto Park Brake definitely engaged.  Of course the coach really didn't have time to reach normal operating temperature in the short 6-8 minute drive.  My friend joined me in the coach and we ran the genny with the galley A/C and had a good chat for about 15-20 minutes.  Then he stepped out, I killed the genny and the A/C and prepared to drive 2 miles home.  When I pushed in the yellow dash knob and shifted into D, again I heard the hydraulic pump kick in and within a few seconds the Auto Park Light went out.  So I began to drive.

On the way home the Auto Park Light began to flash on and off and by the time I got home it was on but dimly lit.  I parked the coach and could immediately smell that the brake pads were starting to burn.  The short drive home was never over 30MPH and I drove maybe a half mile with the Auto Park Brake dimly lit, so I don't believe there was enough heat buildup to cause permanent damage to the brake or pads.  When I shifted into Park and pulled out the yellow knob on the dash, the Auto Park Brake remained dimly lit.

So I began reading everything I could find about the wonderful Auto Park Brake system.  It was obvious to me that I needed to replace my "Rotten Green Switch" so I ordered a few from Amazon and waited.  The existing switch was definitely faulty and had fluid starting to pass through it to the electrical contacts.  It took me about 20 minutes to install the new switch after which everything went right back to how it was when I acquired the coach.  That is, the pump engaged as expected when shifting out of Park and pushing in the yellow know, the Auto Park Light went out as expected, and the brake released as expected.  I tested it on a hill a few blocks from my home, probably 6-8% grade, parking both up hill and down and the Auto Park Brake engaged and held as expected.  Keep in mind that I was just a few blocks from home and therefore nothing was up to normal operating temperature yet.

Then I drove around a bit, about a mile of surface road then two miles of freeway, then another mile of surface road.  This was enough to bring the coach up to normal operating temperature.  And when I shifted into Park and pulled the yellow knob, the brake did NOT engage and the Auto Park Light did NOT illuminate, exactly like it was when I acquired the coach.  So I decided to do more digging, and I engaged expert Roger Haag (oldusedbear) at www.rvautopark.com.  He suspected that perhaps the Auto Park Brake cable was becoming bound/stuck when warm and I initially agreed since my cable makes contact with the back of the engine block right where the tranny bell housing connects.  But then I realized that if the cable was merely stuck, the Auto Park Light would still immediately illuminate when it was supposed to (when shifting into Park or pulling out the yellow knob).  The Auto Park Light doesn't illuminate until the hydraulic pressure is released and drops (so that the actuator spring can decompress and pull the cable to engage the brake).  After the coach sits and cools off for about 5 minutes (and you can almost set your watch by it), you can hear the Auto Park Brake engage over a 15 second series of pops and creaks.

So Roger and I are a little stumped on this one.  I considered the possibility of a bad relay, but that should only effect whether or not the pump engages.  It should have nothing to do with the release of pressure.  The "Rotten Green Switch" just tells the pump to come on if it senses less than 1,200psi of pressure while the shift lever is in Park and the yellow knob is pressed.  Once the shift lever is in Park and/or the yellow knob is pulled, the pressure should be released.

To add a little more to the mystery, I drove the coach about 80 miles round trip to a campground at a nearby lake and everything was as expected (i.e. Auto Park Light stayed off while driving, engaged only after 5 minutes of "cooling off" period once parked).  But then the next day, a particularly hot day (95F) I drove it to a scale house owned by one of my clients (14,540lbs with 3/4 tank of fuel, empty fresh water and holding tanks, a little bit of camping gear).  On the drive back, as soon as I got off of the highway and had less than a mile to go to get home, the Auto Park Light began flashing.  I continued home (less than a mile, less than 30MPH) and parked and again could smell the brake pads starting to burn.  ARGH!  It had only been 100 miles since I replaced the Rotten Green Switch so I figured I somehow blew through another one, perhaps due to over-pressure by the hydraulic pump.

So I let the coach sit for a day or two before I got curious again and fired it up.  This time it was in the evening and probably closer to 80F.  I drove around town for about an hour and the Auto Park Light never illuminated while driving.  I parked several times to see if it would illuminate and engage the brake but the same delay was present.  So I ended up parking it in a lot in a public park and just sitting there with the engine and dash A/C running.  I chocked the wheels even though I was on a level spot and the coach didn't try to roll.  After about five minutes of sitting with the engine running (and therefore maintaining normal operating temperature if not a bit higher than normal due to lack of air flow), I heard the brake engage through the usual 15 second series of pops and creaks.  So the delay really doesn't seem to have anything to do with engine compartment heat but rather heat or pressure build up at the hydraulic pump.

So to all of you experts out there who are still insane enough to be interested in reading this...  What the Hell is going on?  I believe the hydraulic pump is shutting off once there's enough pressure to compress the actuator spring and release the brake.  Why isn't the pressure being relieved as soon as the shift lever is back in Park and/or the yellow knob pulled?  Why does it take several minutes of operation to get to this condition whereby a five-minute delay is needed for the hydraulic pressure to release?  And of course, why would the Auto Park Light come on again while I'm driving but then stay off the next time I drive?  I have 13 days to get this and a few other issues resolved.  :)

--Kevin
 

driftless shifter

Well-known member
Joined
Jun 6, 2012
Posts
2,407
The pops and creaks when engaging when hot tell me something is binding. Maybe brake shoes and levers behind drum are binding and need some brake grease or oldusedbear is correct and the cabke is binding when hot. As far as dim light and light application when hot goes possible valve is tired and leaks under heat. The RGS operates a valve doesn't it? I have the older mechanical system with cams and levers that apply and release. You will become an expert on your system by the time you figure it out.

Bill
 

BoomerD

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Joined
Jun 21, 2014
Posts
1,326
Location
Grays Harbor County, WA
Since your coach is a 2000 model year, I presume you have the 7.4l engine...

Brazel's RV and their ultra rv products line offer a complete air replacement for the hydraulic auto-stop system that's so problematic...

https://www.brazelsrv.com/p32-auto-park-air-system-upgrade-74l-hyd-pump-frame-rail
(they also have a system for the 8.1l engines)

NOT inexpensive...but supposedly a MUCH better system. I'm considering it for my 2003 P32 chassis.

OR, they also offer better hydraulic switches than the old "rotten green" and "rotten brown" switches that were the stock parts.

http://www.ultrarvproducts.com/store/index.php?route=product/product&path=25_115&product_id=213&filter=135

I had them do the dash cluster rebuild when I was there. We chatted for quite a while about some of the other upgrades available for my coach...and I think I'm going to have them do a bit more work for me. I can't speak highly enough about their service.
 

hedhunter9

Well-known member
Joined
Feb 13, 2015
Posts
203
Location
Northern Indiana
Or do like I did... After repeated fix's to my 94 autopark brake system that would only last 1 trip, I decided to scrap it.

Took it to Certified transmission and they put a parking pawl in the tranny for $350.

Works like a dream every time now... No more problems..

Bob
 

GemiNiveK

Well-known member
Joined
Jun 20, 2015
Posts
120
Location
St. Louis
hedhunter9 said:
Or do like I did... After repeated fix's to my 94 autopark brake system that would only last 1 trip, I decided to scrap it. Took it to Certified transmission and they put a parking pawl in the tranny for $350. Works like a dream every time now... No more problems..

Thanks, Bob.  After all of the reading I've done, I'd really love to trash this whole system.  Did you have Certified Transmission completely remove the brake and put in a longer segment of drive shaft, or did they just gut the brake and leave it in?  If they left it in, did they hook it up to some sort of handle so that you can manually apply it?  I'd still want to have a real emergency brake of some sort.  And do you think a tranny pawl is enough to hold 20,000GVWR on any grade?

I've decided that my problem is likely the pressure valve solenoid sticking when it gets hot somehow so that it doesn't open the valve and let off the pressure until the solenoid cools.  But I'm just not sure why it would get hot in the first place.  I don't know much about the guts of that solenoid...yet.
 

GemiNiveK

Well-known member
Joined
Jun 20, 2015
Posts
120
Location
St. Louis
BoomerD said:
Brazel's RV and their ultra rv products line offer a complete air replacement for the hydraulic auto-stop system that's so problematic...

I've considered getting their replacement pressure sensor switches.  But at this point I think my problem is probably the pressure valve solenoid which is an ACDelco part number 15149862 that you can pick up at Rock Auto for $168, Amazon for $189, or UltraRV for $258.  UltraRV doesn't say that theirs is any different from the ACDelco and they even use the same part number on their site so I suspect they're selling the ACDelco, just with a huge mark-up.  I'm all for good folks making some money, but being 45-50% more than the competition seems a little gratuitous to me.  But I suppose that kind of makes sense if they ultimately want folks to just replace the stock J71 Auto Park Brake system with their pneumatic replacement.
 

Gil Penney

Member
Joined
Jul 1, 2019
Posts
9
Yes I know but it sounds like the problem I have and I was wondering what his outcome was Gil
 

Henry J Fate

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Jun 14, 2018
Posts
1,479
You can send the original poster a PM or start a new thread. Starting a new thread is probably best. The original poster has been inactive for almost 4 years.
 

Bmoredad

New member
Joined
Apr 26, 2021
Posts
4
Location
Baltimore md
2004 winnebago siteseer 30b chevrolet workhorse
Hello,
My parking brake is stuck on .it happened last year .I pulled the bolt where the two cables meet . But had a alarm noise while driving. been using lvl system for brake since first trip last year . Could not figure out how to stop alarm . Anyone know how ? I had found a blown fuse .so I put Bolt back in no luck still stuck in park . Ugh not sure if something happened to old bear no answer and site had dead links .
 

Mark_K5LXP

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Joined
Nov 17, 2018
Posts
1,399
Location
Albuquerque, NM
Maybe the moderators could move this to a new topic.

Old Bear is, well, old. From posts on other forums I've read that he's no longer in the business of servicing these brakes. Whatever documentation you can find on his site you should probably archive as no telling how long his site will be up.

Sounds like you may have more than one issue going on. Ultra RV has some parts and service information for the J71 brake. If you're not up to fixing it yourself you may have a challenge finding someone willing to take it on, but it's not a terribly complicated system to figure out.

Mark B.
Albuquerque, NM
 

Bmoredad

New member
Joined
Apr 26, 2021
Posts
4
Location
Baltimore md
Maybe the moderators could move this to a new topic.

Old Bear is, well, old. From posts on other forums I've read that he's no longer in the business of servicing these brakes. Whatever documentation you can find on his site you should probably archive as no telling how long his site will be up.

Sounds like you may have more than one issue going on. Ultra RV has some parts and service information for the J71 brake. If you're not up to fixing it yourself you may have a challenge finding someone willing to take it on, but it's not a terribly complicated system to figure out.

Mark B.
Albuquerque, NM
Thanks Mark,Glad he's okay I got help from him a few years ago . I can't remove it or move it I'll copy and post .not to good at this here goes .I plan to do myself lol .
 
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