parking brake not holding

Topic: parking brake not holding (Read 1883 times) previous topic - next topic

parking brake not holding

May 15, 2022, 12:57:05 pm

My parking brake is not holding. Brakes seem to work fine when stopping the coach, but, when parking brake is engaged on an incline the coach rolls forward/backward.

A truck mechanic here in Tucson tells me it is because my rear brakes are worn out. Any opinions or past experience? Ideas re: cost of brake job on rear brakes?

This is on a 1993 U225.

Roger

Re: parking brake not holding

Reply #1 – May 15, 2022, 01:01:38 pm

Roger,

Have you looked at how much brake lining is left?

Not sure without seeing it that we can give you sage advice.

Your coach has wedge drum brakes-- also popular on medium duty trucks, especially in Europe. Pretty basic system.

Re: parking brake not holding

Reply #2 – May 15, 2022, 01:51:46 pm

Rears wear out first because of weight. I had mine done in Palm Springs and it wasn't expensive.

Re: parking brake not holding

Reply #3 – May 15, 2022, 02:08:45 pm

And, although the air wedge brakes DO have automatic adjusters, at that age they may not be working and may need to be serviced.

Start by verifying the amount of brake shoe left.

BTW the manual does call for cleaning and lubing the adjusters ever 100.000 miles.

Re: parking brake not holding

Reply #4 – May 15, 2022, 07:22:43 pm

Every 100,000 miles!!!
WOW, that is like every other day!!

Re: parking brake not holding

Reply #5 – May 15, 2022, 08:36:40 pm

Here is a PDF for how to check and adjust your slack adjusters: https://cbsparts.ca/admin/bulletins/Meritor%20TP9173.pdf

Pierce

Re: parking brake not holding

Reply #6 – May 15, 2022, 09:09:16 pm

Slack adjusters are not your problem. If the brake doesn't hold, baby needs new shoes.

Re: parking brake not holding

Reply #7 – May 15, 2022, 09:29:56 pm

NO. We have answers above to both OP's Meritor/Rockwell air wedge drum brakes and the air disk brakes used on other coaches.

They are not the same and their "care and feeding" is different.

Re: parking brake not holding

Reply #8 – May 15, 2022, 10:10:55 pm

I had one side with no park brake along with poor drive brake. The little rachet paw thingy had backed out. Serviced the wedge as well as the dual pancakes.
Plenty of shoe left at 150K . Its really hard to get to the adjusters. I made a bent spoon with the drum removed and practiced a couple of times. Adjusted it as big as I could fit the drum on. Now they stop as well as its supposed to.

Re: parking brake not holding

Reply #9 – May 16, 2022, 01:38:19 am

Quote from: wolfe10 – May 15, 2022, 01:01:38 pm

Roger,

Have you looked at how much brake lining is left?

Not sure without seeing it that we can give you sage advice.

Your coach has wedge drum brakes-- also popular on medium duty trucks, especially in Europe. Pretty basic system.

I have not personally looked at the brake linings. I meet with the mechanic tomorrow, Monday 1/16.

Re: parking brake not holding

Reply #10 – May 16, 2022, 06:21:38 am

Quote from: Doug W. – May 15, 2022, 08:10:01 pm

Dang, guess I'm over greasing my slack adjusters oh well grease is cheap. Seriously something is a bit off with that statement. They should be greased a minimum of every oil change interval just like front end components and drive line.

Servicing the Meritor wedge brake is a little bit different than "S" cam brakes.

In operation wedge brakes work more like traditional hydraulic brakes, but in place of a hydraulic cylinder you'll find a traditional air can operating a wedge applying force to the brake shoes.

Servicing these or more akin to cleaning and lubing a watch than traditional air brakes with multiple lubricants involved, all sealed away from the elements.

General service manual PDF:

http://manuals.chudov.com/Grove-Rough-Terrain-Crane/Meritor-Wedge-Brakes.pdf

FWIW, when I sent Lynn to Texas to survey and purchase our new home, I packed a 3/4" wrench in his travel bag.

After he arrived home and I slid underneath to inspect our new toy, I said something akin to "what is going on here?"

Much reading ensued.

Re: parking brake not holding

Reply #11 – May 16, 2022, 12:52:46 pm

This is an interesting topic. The only kind of air brakes I had ever worked on before this coach
was S cam brakes. On this coach is the first time that I have worked on air disk brakes which I
don't think are that common as a friend had never worked on him or his brother who had owned
a truck shop had never worked on them either.

Re: parking brake not holding

Reply #12 – May 16, 2022, 01:14:38 pm

Fire trucks are another application where you will fine air disk brakes.

But, the OP has a completely different system-- Rockwell/Meritor air drum wedge brakes. Remember, the U225 is substantially lighter than your 1999 U320.

Re: parking brake not holding

Reply #13 – May 16, 2022, 08:44:42 pm

Quote from: Pierce & Gaylie Stewart – May 15, 2022, 08:36:40 pm

Here is a PDF for how to check and adjust your slack adjusters: https://cbsparts.ca/admin/bulletins/Meritor%20TP9173.pdf

Pierce

Pierce, this is for "S" cam brakes. The wedge brake system uses a completely internal automatic adjustment.

Re: parking brake not holding

Reply #14 – May 16, 2022, 11:52:53 pm

My mechanic seems to think I have an S cam system. Is that possible? Is he blowing smoke? I really don't know. He works on a lot of big trucks; semis.

Re: parking brake not holding

Reply #15 – May 16, 2022, 11:58:05 pm

He can see what we are only supposing. If he is a good truck mechanic he will know the difference, there is no reason for him to mislead you.

Re: parking brake not holding

Reply #16 – May 17, 2022, 12:07:45 am

My 87 had both. S on the front and wedge on the rear. Or vice versa, I forget. You will know once the wheel is pulled.

Re: parking brake not holding

Reply #17 – May 17, 2022, 12:19:01 am

You don't have to pull the wheel to tell the difference. If the diaphragm goes directly into the backing plate wedge. If a shaft comes out s cam.

Re: parking brake not holding

Reply #18 – May 17, 2022, 08:37:33 am

Quote from: rworley – May 16, 2022, 11:52:53 pm

My mechanic seems to think I have an S cam system. Is that possible? Is he blowing smoke? I really don't know. He works on a lot of big trucks; semis.

And some people make assumptions, as in, "RV Owner's are idiots."

After the arrival of our new home, I slid underneath and took a peek. When I saw the cans bolted right to the backing plate I knew I had some reading to do. (Lucy)

Re: parking brake not holding

Reply #19 – May 17, 2022, 08:47:37 am

If your 1993 U225 has anything but wedge brakes, it will be the very first I have either seen or heard of.

Re: parking brake not holding

Reply #20 – May 17, 2022, 10:19:50 am

I have cam fronts and wedge rear.

Re: parking brake not holding

Reply #21 – May 17, 2022, 11:23:25 am

Quote from: Protech Racing – May 17, 2022, 10:19:50 am

I have cam fronts and wedge rear.

Again, COMPLETELY different chassis.

Re: parking brake not holding

Reply #22 – May 17, 2022, 08:56:37 pm

If he is not familiar with the wedge brakes you better look for someone who is. They might only need to be adjusted or the spring brake might be broken. You shouldn't pay for his education.

Re: parking brake not holding

Reply #23 – May 18, 2022, 01:31:02 am

Quote from: wolfe10 – May 17, 2022, 08:47:37 am

If your 1993 U225 has anything but wedge brakes, it will be the very first I have either seen or heard of.

Well after talking to the mechanic again today and having him assure me that my brake system is an s cam system, I dug out my manuals. According to my manuals my brake system is a Rockwell wedge system.

My coach has been at the shop for six days and has only been moved once. It was supposed to be done yesterday, then later today; now tomorrow by noon. I suspect the mechanic has not looked at the coach; maybe one of his guys has. Needless to say I'm very frustrated.

Re: parking brake not holding

Reply #24 – May 18, 2022, 07:30:13 am

Quote from: rworley – May 18, 2022, 01:31:02 am

Well after talking to the mechanic again today and having him assure me that my brake system is an s cam system, I dug out my manuals. According to my manuals my brake system is a Rockwell wedge system.

Maybe it's time to call around to other truck shops and mobile mechanics? There is some specialized knowledge necessary to changing the brake shoes and resetting the automatic adjusters, and personally, I don't want a mechanic learning on my nickel with my equipment.

I find it best to meet in person, that way I can watch their eyes for that "Deer in headlights" look as they realize that they have no idea what I'm talking about. right before they answer, "Sure, No Problem!" in a confident voice.

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