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Topic: 03' U320 Park brake not holding (Read 528 times) previous topic - next topic

03' U320 Park brake not holding

We have an 03' U320 and the park brake is not functioning properly.  I've tried to do the adjustment routine where you hold the brake pedal to the floor repeatedly six times.  That works for a little while but doesn't last.

During driving the brakes seem to work just fine.  But put on the park brake, stick the transmission in drive, and it starts to creep forward.

It's highly concerning because if we were stuck on a hill in traffic, the air brakes wouldn't hold indefinitely.

Any ideas what's going on here?  Thanks!
2003 U320 38' tag
2003 Green Jeep Wrangler

Re: 03' U320 Park brake not holding

Reply #1 –
Have you verified that the caliper is auto adjusting up? Calipers and slide pins are to be serviced every couple years. I would recommend getting into manual and properly checking adjustment on caliper.
Scott

Re: 03' U320 Park brake not holding

Reply #2 –
The rear slack adjusters are supposed to automatically adjust. Yours might not be working. Put your safety stands in and block the wheels then measure how far the rod comes out with someone pushing on the brakes. Anything over 2" and they are out of adjustment. Mine will creep in gear in reverse when first starting out for the day but when warmed up hold.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: 03' U320 Park brake not holding

Reply #4 –
What is your engine rpm at idle?  If too high it could overcome the parking brakes.
On my '99 the idle speed is set using the cruise control and is easy to inadvertently adjust the speed up. 
Forest & Cindy Olivier
1987 log cabin
2011 Roadtrek C210P
no longer 1999 36' U320 build #5522
2013 Rzr 570 & 2018 Ranger XP1000
2006 Lexus GX470
2011 Tahoe LT 4x4
Previous 1998 45' 2 slide Newell, 1993 39' Newell

Re: 03' U320 Park brake not holding

Reply #5 –
Quote from: coloradomtn –
It's highly concerning because if we were stuck on a hill in traffic, the air brakes wouldn't hold indefinitely.
The "air brakes" and the "parking brakes" employ two different means of applying the same braking devices (calipers and pads).

Air brakes (all 4 corners) are applied by air pressure.  As long as you have sufficient air pressure the air brakes should hold.

Parking brakes (rear axle only) are applied by mechanical spring pressure.  Using THESE is where you might have a problem on a hill.

Heavy duty chocks are recommended safety equipment on all coaches.  I carry two pair of chocks (4 total) - use any time we park on a steep grade.

https://www.harborfreight.com/rubber-wheel-chock-with-eyebolt-69828.html



1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: 03' U320 Park brake not holding

Reply #6 –
The parking brake is only intended for flat ground or a very slight slope. I have a pair of the HF chocks exactly like the ones Chuck has. I store them in the retractable step compartment so I can pull them out when I step out of the coach. Unless the ground is flat or has a VERY slight slope I put them around the wheels. A short line holds the two together and makes it east to pull them out of the compartment.

The springs in the cans are very small and meant for flat parking only and will do almost nothing in an emergency. They are not as effective on disk brakes as compared to drum brakes.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: 03' U320 Park brake not holding

Reply #7 –
I NEVER trust the brake chamber springs to hold on any slope!
I found that if I adjust the rear slack adjusters to make contact (brake pads) with the rotor and then back off 1/2 turn it seems to help.
I wish larger brake chambers could be installed.
I never forget the old story about the guy who bought a new to him Wonderlodge that ended up going over a mountain cliff when his parking brake did not hold.
1995 U320C SE 40'
Jeep 4x4 Commander - Limited - Hemi
"The Pack"  Yogi and Diesel our Airedales -  Charlie our Boxer/Akita mix. Gone but NEVER forgotten Jake our yellow Lab.
NRA Law Enforcement Firearms instructor - Handgun/shotgun
Regional Firearms instructor for national Armored Transp. Co.

Re: 03' U320 Park brake not holding

Reply #8 –
Larger cans for the back can be purchased but will change the front to rear bias making the rear more prone to lock up before the front especially in wet weather. Don't think the springs would be any larger though so nothing gained when parking.

I remember our later fire trucks with 10 inch drums. The Anchor Lok parking brake was very effective but we always chocked the rear driver's side. Many stories have been told about trucks/buses going over a bank.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)
 

Re: 03' U320 Park brake not holding

Reply #9 –
Thank you guys so much for the timely and informative replies!  Sorry, it has taken until now for me to respond.  We are selling our house, and getting everything ready for the photos had turned into a much bigger job than expected over the past week.

From reading the replies, it's clear to me that I didn't know how the park brake worked.  I wrongly assumed it was integrated with the service brake.  Guess it's only the service brake that is fail-safe.  That would explain a lot about those photos of sinking MH's at the boat ramps!  Moving forward (pardon the pun), I will be a lot more careful parking on a slope.

This house move came out of nowhere, as we normally travel in the winter.  We have a serious time crunch to get our place sold, or we will lose the contract on the new place.  No time to troubleshoot this, as long as I can drive the motor home safely, I can just chock the wheels if there's an issue with the park brake.

Not exactly sure what we are going to do with the motor home over the winter when we will be busy moving (hopefully).  I'll be posting up about that (storage or winterizing) once we get our house under contract.

Thanks again!
2003 U320 38' tag
2003 Green Jeep Wrangler