Park Brake not holding

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Park Brake not holding

August 09, 2012, 01:12:41 am

As of today, the park brake is not holding when the transmission is in D or R at idle. I was on just the slightest incline, but this is a change. We are making sure the wheel chocks are handy!
Can this be adjusted?
Thanks, Dick

Re: Park Brake not holding

Reply #1 – August 09, 2012, 06:43:18 am

Dick, sounds like your rear brake (slack adjusters) are out of adjustment, they are auto adjusting however they sometimes need to be manually adjusted. The adjustment specs can be found in you owners manuals. Or you have a rear axle seal leaking oil on the brake pads. Look on the inside of the rear wheels for any oil leaking.

Re: Park Brake not holding

Reply #2 – August 09, 2012, 07:59:10 am

If there is no oil leak and rotor and pads look normal, you can try to adjust the auto slack adjusters by applying several hard all the way to the floor brake applications while stopped. I found something similar with my parking brake from light brake use. Holding power increased after doing the above procedure. Easier than manual adjustment.

Re: Park Brake not holding

Reply #3 – August 09, 2012, 09:23:23 am

You might check to see if your Smart Wheel is set for high idle. That would make it more difficult for the parking brake to hold when the transmission is in gear.

Re: Park Brake not holding

Reply #4 – August 09, 2012, 09:57:13 am

Quote from: Jerry Whiteaker – August 09, 2012, 07:59:10 am

If there is no oil leak and rotor and pads look normal, you can try to adjust the auto slack adjusters by applying several hard all the way to the floor brake applications while stopped. I found something similar with my parking brake from light brake use. Holding power increased after doing the above procedure. Easier than manual adjustment.

My understanding is that the parking brake should be released before making a hard application of the service brake.

Perhaps one of the experts on the forum could confirm or refute that advice.

Re: Park Brake not holding

Reply #5 – August 09, 2012, 10:02:59 am

J.D.

If the air brake system has an ANTI-COMPOUNDING valve it doesn't matter. If it doesn't, you are correct, do not apply hard service brake PLUS parking/emergency brake at the same time.

With such a wide range of year models and different chassis owned by forum members, would hate to generalize unless it is to say you are always safer NOT applying service brake hard while parking brake is still engaged.

Brett

Re: Park Brake not holding

Reply #6 – August 09, 2012, 10:29:59 am

My slack adjusters are OK but the parking brake will not hold on much of a hill. Many times I have had to select reverse (or leave it in drive) before I got out to chock the wheels on hills. The parking brakes only have a spring inside the can on each side in to apply the rear brakes so don't expect too much. But check the adjusters as they may not be doing the "auto" thing. Excellent instructions/illustrations for the procedure are in the brake section of the black Foretravel manual.

I can't go down the steep part of my driveway without selecting neutral even with max application of the service brakes and full air pressure.

Arriving at the scene of an emergency, I would be close to locking up the wheels and 30 feet or so away on several apparatus, I would apply the parking brake. Never had any problems doing that. I also know first hand that if you heat the brakes enough to get severe fade, applying the parking brake does absolutely nothing

Pierce

Re: Park Brake not holding

Reply #7 – August 09, 2012, 12:45:31 pm

Yes, I agree that the safe thing to do is to release the parking brake before applying a full pedal stroke and be on level ground so you do not roll. Eliminates the worry about whether there is an anti-compounding valve or not. I have a wooden stick that I cut to a correct length that can be wedged between the brake pedal and the underside of the dash. It stays on the floor next to the drivers seat. It's just for the time that I might need to park on a steep incline and expect the parking brake will not hold. So far haven't had to use it.

Re: Park Brake not holding

Reply #8 – August 09, 2012, 01:59:30 pm

So far I can rule out 'high idle' as a cause. Pierce, my white owner's manual does not have that kind of information on the brakes. I would like to see that if you have a way to scan it.
I am taking the coach in for service on the dash A/C in the morning and will probably have them look at that brake while I'm there.

Re: Park Brake not holding

Reply #9 – August 09, 2012, 03:14:24 pm

Dick,

Mine is in the black Foretravel 3 ring binder with the manufacturers info on the rear end, transmission, steering and brakes. My 1993 U300 has a Rockwell parts and a separate maintenance book for the brakes. These are not put out by Foretravel but published by each manufacturer.

Heading to river city now but will photo and post later. Hope your brakes are the same as mine.

Pierce

Re: Park Brake not holding

Reply #10 – August 09, 2012, 05:50:35 pm

Hi Dick,
A few points on the brakes,
1-The parking brakes will not hold when in drive and give it enough fuel, If the brakes did hold securely, and you steped on the fuel, you can destroy U Joints, Driveshaft or Ring & Pinion, have seen it done. The torque converter provides massive torque to the driveshaft from idle up, remember the engine has 1450 ft lb torque, multiply that many times, the drive shaft will turn.

2- For sure check the slack adjusters 2 on drive axle, 2 on front axle, also make sure or have checked, and have the calipers and pads checked.

3-There is the Repair manual in the posted section on this Foreforums site, maybe someone (Michelle) will copy it here for all to see. For some reason I forgot how to move it here.

Good luck and hope the A-H is keeping the water hot enough for Rocky.
Dave M

Re: Park Brake not holding

Reply #11 – August 09, 2012, 11:02:25 pm

Thanks Dave and Rockey continues to have hot showers!
Pierce, those manuals were not included in our owners manual. I have Meritor manuals on the brakes, but they cover two or three models and I'm not sure exactly what I have. If you got the Rockwell parts and maintenance manuals with the coach you can be pretty sure it is specific for your coach.
When I had the brakes looked at for overheating recently, the tech couldn't ID the caliper and FT never returned their phone call.
Maybe someone has the part numbers and mfgr. of the foundation parts for our '03?

Re: Park Brake not holding

Reply #12 – August 11, 2012, 07:54:28 pm

I had the brakes checked yesterday and the automatic slack adjusters manually adjusted. All were out of adjustment (adjustment defined as pads very tight against the rotors and then backed off 1/2 turn). The front axle was very close and the tech pointed out that they need to be adjusted exactly the same on both ends of this axle, else it will pull left or right. Drive axle was quite a bit out of adjustment and this is the only axle with park/emergency brake cans. The tag was out but not as bad as the drive axle.
This is an easy adjustment with the right tools, which I have ordered (See attached). There is no evidence of leaking seals.
This tech also told me it is possible to change the can on the tag axle to one with a park brake chamber. $70 ish for the can, fitting and a valve. Has anyone done this? Seems like it would sure give the park brake a bunch more grip.
Dick

Re: Park Brake not holding

Reply #13 – August 11, 2012, 08:01:48 pm

The disadvantage to the tag having a park brake is when you level the coach and it raises or lowers the tag can not roll and therfore makes a binding which makes for loud popping noises, that some people object to. Country Coach has this type of set up.

Re: Park Brake not holding

Reply #14 – August 11, 2012, 09:13:54 pm

Thanks Ron,
It sounds like you have had that experience. Does that popping continue as long as the air leveling is active, ie whenever it makes small adjustments?
I have been killing the leveling once the coach is level using the emergency stop.
I wonder if that noise is a deal breaker; I think I would rather have the park brake hold tight and just put up with the noise. I can't really decide, but I 'm sure thinking about it. $:-\$

Re: Park Brake not holding

Reply #15 – August 11, 2012, 09:34:12 pm

Dick,

If the parking brake doesn't hold properly, you may be able to adjust or replace the springs that are currently on the coach. More pad and disk area are effective for dissipating energy. More pressure is would be effective for keeping the wheels from turning when parked. Additional cans with parking mechanisms would provide more emergency braking in case of loss of air pressure. They might not provide a more effective parking brake.

I recommend that you check on additional adjustments to your current installation before adding parking cans to the tag. "Real" experts can speak with more experience, knowledge, and authority than I (a pseudo-wannabe-expert.

)

Re: Park Brake not holding

Reply #16 – August 11, 2012, 11:17:09 pm

I like the idea of the added cans on the tag axle, however I am wondering if anyone knows the setup of the tag axle, meaning how much the distance between the two axles changes from the lowest to the highest setting ?
I think I wouldnot object to a little squeaking during the leveling in order to have a more secure anchor.
Maybe CountryCoach has a different setup requiring the distance change between axles. ?
Dave M

Re: Park Brake not holding

Reply #17 – August 12, 2012, 09:34:09 pm

I think that the distance the coach moves could be measured at the front wheels as they are free to rotate and the rear wheels remain stationary. When the coach is moved from all the way down to all the way up you might be surprised to see how far the coach actually moves. And yes you would get popping noises as the coach settles and relevels, my experience from working on country coaches.

Re: Park Brake not holding

Reply #18 – August 12, 2012, 11:15:15 pm

So if DW sits with her foot firmly planted on the service brake and levels the coach from travel height, could I stand outside and get an idea of noise?
Could also observe how much the tag moves relative to the drive axle.
BTW, I walked over to talk to a CC Magna owner last night only to realize at the last minute that his coach didn't have a tag.

Re: Park Brake not holding

Reply #19 – August 13, 2012, 07:19:37 am

From what I have read the parking brake should have about 25-30% of the full braking power of the rear brakes. The spring of the parking brake takes approximately 2,500 lbs of force to fully compress, and applies about 1,000 lbs to the brake linkage. The top reasons parking brakes don't work, slack adjustment, contaminated pads,glazed pads and or rotor,or broken parking brake springs. All but the last mean there is a problem with the rear brakes . gam

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