Brake problem

Topic: Brake problem (Read 1070 times) previous topic - next topic

Brake problem

August 03, 2013, 11:54:18 pm

My first outing this year exposed a bad air bag. After a closer look they all looked borderline so I have spent a good part of this summer working on replacing all the air bags and finishing up a long list of other mechanical and cosmetic projects in and outside of the coach.

finally, today I was ready for a couple days of camping. I drove to the expressway and went about 1 block, I then saw smoke starting to come out of the drivers rear wheel well. I pulled off the expressway and into a paring lot. I found the brake caliper dragging on the rotor.

I got home and inspected. The caliper/pad were contacting the rotor with 0 clearance. I backed off the slack adjuster. I never had a problem like this till I started to do the prescribed 5 hard brake push routine while in storage ( with parking brake off). I thought that some how this practice had adjusted this slack adjuster right up to the rotor, is this possible?

I also discovered that now I have no parking brake. Up to this point the parking brake held good, now nothing.

I test drove the coach after adjusting the slack adjusters (3/4 turn out from rotor contact) nothing was dragging, the front brakes were about 165 degrees ( after several miles of on and off city driving/braking), the rears were about 90 degrees (like they hardly did any braking at all).

What do you think the problem is with the emergency brake, why would 1 slack adjuster tighten up against the rotor and the others did not.

Thanks for your advice.

Re: Brake problem

Reply #1 – August 04, 2013, 12:02:45 am

There is a manual here on the forum on how to adjust the brakes sounds like they are now to loose

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Re: Brake problem

Reply #2 – August 04, 2013, 08:43:22 am

The first brake to fail on our coach's is usually the one with the Park brake. The spring does not like being deployed all the time.

Re: Brake problem

Reply #3 – August 04, 2013, 11:21:00 am

Thanks for putting the manual link on my post, probably Michelle.

Re: Brake problem

Reply #4 – August 04, 2013, 11:43:49 am

We had similar problem with brake on drive axle street side. Our extended service contract replaced the entire caliper, which we did at FOT earlier this year. Service techs had diagnosed it as a problem with the slide pins. In fact they had replaced them before they got word to replace the whole caliper assembly.
There are some posts here on servicing the slide pins. Good luck and please post your resolution.

Re: Brake problem

Reply #5 – August 04, 2013, 12:38:11 pm

Quote from: red tractor – August 04, 2013, 11:21:00 am

Thanks for putting the manual link on my post, probably Michelle.

Nope - Barry B. gets the credit

Re: Brake problem

Reply #6 – August 04, 2013, 02:56:20 pm

How often are the air chambers serviced or replaced?
What are the symptoms when a air chamber malfunctions?
I noticed that one (right)rear air chamber is a long throw design, all the other air chambers are short throw.

RED TRACTOR;
I originally had the slack adjusters set to 1/2 turn out from caliper contact. When I loosened the left rear that had drawn to no clearance I thought I would give all the calipers a extra 1/4 turn out and see how that would effect the performance.

Re: Brake problem

Reply #7 – August 04, 2013, 04:19:44 pm

I'm certainly no expert on brakes but it sounds like the pin was sticking on that one brake that caused the smoking on the expressway. The slack adjuster was released to free it, then later the pin freed itself and the adjustment was then too loose causing the parking brake to be ineffective. Only puzzling part is you still should have had a good parking brake on the passenger wheel. If I remember correctly, the air chamber rod should move about an 1" or 1-1/4" between the parking brake being released and applied - might be a good secondary check.

Re: Brake problem

Reply #8 – August 11, 2013, 10:45:01 am

Seems the rear axle gets all of the debris (for obvious reason).

Guide pins are lubed with a clay hi-temp grease that is a vacuum for dirt. Truckers w/drum brakes don't have this worry & btw this is another of the reasons disc brakes are not typically on OTR rigs.

Inspection of (especially) rear disc brakes (and guide pins) should be a regular part of an inspection program. Much cheaper to pull the rear tires for inspection/pin cleaning than replacing the brake assembly. By the time it's discovered you have guide pin issues the party is over and your pocketbook will be much lighter with needing to replace pads & rotor(s).

Look at the condition of the rotor and make sure no fluid (gear lube) is present and you are good to go. pc

Re: Brake problem

Reply #9 – August 11, 2013, 11:05:20 am

I thing only silicone spray or nothing at all should be used on the guide pins , not grease of any kind. Gam

Re: Brake problem

Reply #10 – August 11, 2013, 12:59:19 pm

From my standpoint the liability of not following protocol is a professional issue.
Working on most everything for over 4 decades to put bread on the table and keep the wolf away from the door is in fact my rule of thumb.

When I perform a service for a customers vehicle that is other than by the book, the door to a liability issue is the hammer by which I exist.

My input concerning this forum is from this prospective.

Your decisions concerning procedures from my prospective matter not.

With Respect,
pc

Re: Brake problem

Reply #11 – August 11, 2013, 01:36:58 pm

With respect. That's why I always use, I think ,or I believe when I post anything. Meritor revised the guide pin clean and lube on 04-05 . I don't know if this is the latest revision but it reads lube slide pins with light amount of WD-40 { I will not use WD -40 I think it holds water and will gum up } CRC silicone spray or similar product. Like most of us they found out that dirt sticks to grease. Gam

Re: Brake problem

Reply #12 – August 11, 2013, 03:53:45 pm

Quote from: gam – August 11, 2013, 01:36:58 pm

I will not use WD -40 I think it holds water and will gum up
Quote from: Lon and Cheryl – August 03, 2013, 11:54:18 pm
I found the brake caliper dragging on the rotor. The caliper/pad were contacting the rotor with 0 clearance. I backed off the slack adjuster. I never had a problem like this till I started to do the prescribed 5 hard brake push routine while in storage ( with parking brake off). I thought that some how this practice had adjusted this slack adjuster right up to the rotor, is this possible?

According to this article WD-40 is supposed to displace water and the WD in the name is for Water Displacement. WD-40 - Wikipedia, the free encyclopedia

Regards the problem with the slack adjuster, they can fail like any other mechanical part. The caliper holding the pads can get stuck on the guide pins and drag. That happened on my right rear brake. Although the rear rotor and pads are the same size as the front brake rotor and pads the rear brakes have a larger air chamber and the push rod exerts much more force on the slack adjuster arm. It's braking 2 wheels and there is more weight on the rear axle, so the rear brakes do more work than the front brakes, so they should get hotter during braking than the front. If the retarder is in use the load on the rear brakes is reduced some. If there is too much slack in the adjuster, less braking force is applied and this also effects the braking brake. If the parking brake is not holding, too much slack or a broken spring in a parking brake chamber could be the cause. On level ground with the parking brake applied the coach should not move in 1st gear up to about 1000 engine rpm. Not sure if this is true for all coach models, but mine is like that. Since you have no parking brake after you made the adjustment, I suspect the slack adjustment is incorrect.

Re: Brake problem

Reply #13 – August 12, 2013, 01:17:23 am

My parking brake was holding fine until I took the MH out initially. When I let it cool and crawled under to check the slack adjustment I found I had no parking brake function at either rear wheel. I backed the slack adjuster off so that I had 1/2 turn off the rotor.
I bought a 20 ton air /hydro jack and a 3/4" 1000# impact and sockets this weekend.I will pull the wheels next weekend and take a look.
I'm SURE I will have LOTS of questions to ask after that stage.

Re: Brake problem

Reply #14 – August 12, 2013, 07:42:07 am

PROJECT!

I have to do mine plus rear seals.

Re: Brake problem

Reply #15 – August 12, 2013, 12:32:10 pm

Quote from: Lon and Cheryl – August 12, 2013, 01:17:23 am

My parking brake was holding fine until I took the MH out initially. When I let it cool and crawled under to check the slack adjustment I found I had no parking brake function at either rear wheel. I backed the slack adjuster off so that I had 1/2 turn off the rotor.
I bought a 20 ton air /hydro jack and a 3/4" 1000# impact and sockets this weekend.I will pull the wheels next weekend and take a look.
I'm SURE I will have LOTS of questions to ask after that stage.

I suggest that you download and print out this brake service manual. It will probably answer most of your questions. http://beamalarm.com/foretravel-links/PDF/brakes-maintenance-manual-mm4m.pdf Be careful when you jack up the wheels that the coach is properly supported and chocked so it can not roll.

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Brake problem

August 03, 2013, 11:54:18 pm

Re: Brake problem

Reply #1 – August 04, 2013, 12:02:45 am

Re: Brake problem

Reply #2 – August 04, 2013, 08:43:22 am

Re: Brake problem

Reply #3 – August 04, 2013, 11:21:00 am

Re: Brake problem

Reply #4 – August 04, 2013, 11:43:49 am

Re: Brake problem

Reply #5 – August 04, 2013, 12:38:11 pm

Re: Brake problem

Reply #6 – August 04, 2013, 02:56:20 pm

Re: Brake problem

Reply #7 – August 04, 2013, 04:19:44 pm

Re: Brake problem

Reply #8 – August 11, 2013, 10:45:01 am

Re: Brake problem

Reply #9 – August 11, 2013, 11:05:20 am

Re: Brake problem

Reply #10 – August 11, 2013, 12:59:19 pm

Re: Brake problem

Reply #11 – August 11, 2013, 01:36:58 pm

Re: Brake problem

Reply #12 – August 11, 2013, 03:53:45 pm

Re: Brake problem

Reply #13 – August 12, 2013, 01:17:23 am

Re: Brake problem

Reply #14 – August 12, 2013, 07:42:07 am

Re: Brake problem

Reply #15 – August 12, 2013, 12:32:10 pm

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