Brake pad replacement now overheating rr brake

[gweedo295]

you say the caliper is free, how did you test that, by compressing it? doesn't mean its free.

I don't know but is your parking brake different from your brake pads, like an internal shoe?

when you checked the brakes for heat did you check the pads or the parking brake?

You mentioned air brakes, I'm assuming that is for your parking brake, have you changed your desiccant filter for the air brakes?

Have you ever bled in new hydraulic fluid

if you have disc brakes have you checked to see if you have a portioning value that sends the fluid to each wheel and is it working

Just a couple ideas, good luck to you..

[joeplazek]

Originally Posted by gweedo295

you say the caliper is free, how did you test that, by compressing it? doesn't mean its free.

I don't know but is your parking brake different from your brake pads, like an internal shoe?

when you checked the brakes for heat did you check the pads or the parking brake?

You mentioned air brakes, I'm assuming that is for your parking brake, have you changed your desiccant filter for the air brakes?

Have you ever bled in new hydraulic fluid

if you have disc brakes have you checked to see if you have a portioning value that sends the fluid to each wheel and is it working

Just a couple ideas, good luck to you..

This set up is Meritor Air Disc Brake. Parking brake and service brake works totally through the same caliper and pads. There is no brake fluid since its air brake. I am checking the pads for heat with a pistol type infra red temp gun. Its one brake acting up only (right rear). Its been since I changed the pads. We are starting to believe its a wrapped rotor. Just haven't been able to shake free enough time to get back working on it. I reached out here to see if anyone have seen the same kind of problem and can steer me in the right direction before I lose whats left of my hair. It would just save me some trial and error time. Like I said earlier I have done brake pads on this before and followed the same procedure. I am getting ready to put the right rear wheels back on adjust to a looser brake adjustment and see if the heat goes away. If it does I can assume it is a wrapped rotor as bearing adjustment is good. Its really the only thing it can be now.


joe

[MrMark52]

I’ve never worked on air brakes before, nor do I remember driving a vehicle with air brakes - so I only hope to be a sounding board for though after reading through the Meritor Air Disc Brake Service manual.

1. I would think if you had a warped rotor that you could/would feel it in the brake pedal upon lite braking, just as you can with hydraulic brakes.

2. What is the fail-safe mode for the brakes? I’m pretty certain on tractor-trailer trailers and railroad cars the brakes require air pressure to release the brake.
If that is the case with your coach (i.e. setting of emergency brake), then maybe you’ve got a leaky cylinder on that wheel.

3. Or - if it’s not fail-safe braked as described above, you could either have a weak spring return for the air cylinder - which makes Wolfe10’s solution more plausible - especially since there appears to be a kit for just such an occurrence.

4. I know on hydraulic systems that disc brake adjustment is pretty much automatic. Of all disc brake systems I’ve ever worked on, I’ve not seen any type of adjuster or spring return mechanism, nor an adjuster much like was found on drum brakes.
So not sure quite how your going to “loosen the adjustment”. And not sure how why that if you adjusted one side without issue, why you couldn’t get the other side adjusted properly without issue after multiple tries.

5. I’m really leaning toward something limiting the air cylinder stroke or limiting the lever arm rotation (assuming there is a lever arm that the air cylinder is attached), or limiting the brake pad cradle return travel that you might be able to overcome by hand, but the system can’t overcome on its own.

Just a thought - have you tried jacking the coach up, removing the tires to access the caliper and measuring the pad/disc clearance before and after you try to manually move the cradle one direction or the other.
Then, get some air pressure up and have someone depress the brake pedal while you watch the cradle movement. See if it returns to where you left it. Measure the clearances again. Cycle the brakes several times while watching everything that moves - pad cradle, air cylinder stroke, etc., etc..
Hopefully we’re not talking thousands of an inch movement and you will be able to see variances by eye.
But then maybe not.

[joeplazek]

Originally Posted by MrMark52

I’ve never worked on air brakes before, nor do I remember driving a vehicle with air brakes - so I only hope to be a sounding board for though after reading through the Meritor Air Disc Brake Service manual.

1. I would think if you had a warped rotor that you could/would feel it in the brake pedal upon lite braking, just as you can with hydraulic brakes.

2. What is the fail-safe mode for the brakes? I’m pretty certain on tractor-trailer trailers and railroad cars the brakes require air pressure to release the brake.
If that is the case with your coach (i.e. setting of emergency brake), then maybe you’ve got a leaky cylinder on that wheel.

3. Or - if it’s not fail-safe braked as described above, you could either have a weak spring return for the air cylinder - which makes Wolfe10’s solution more plausible - especially since there appears to be a kit for just such an occurrence.

4. I know on hydraulic systems that disc brake adjustment is pretty much automatic. Of all disc brake systems I’ve ever worked on, I’ve not seen any type of adjuster or spring return mechanism, nor an adjuster much like was found on drum brakes.
So not sure quite how your going to “loosen the adjustment”. And not sure how why that if you adjusted one side without issue, why you couldn’t get the other side adjusted properly without issue after multiple tries.

5. I’m really leaning toward something limiting the air cylinder stroke or limiting the lever arm rotation (assuming there is a lever arm that the air cylinder is attached), or limiting the brake pad cradle return travel that you might be able to overcome by hand, but the system can’t overcome on its own.

Just a thought - have you tried jacking the coach up, removing the tires to access the caliper and measuring the pad/disc clearance before and after you try to manually move the cradle one direction or the other.
Then, get some air pressure up and have someone depress the brake pedal while you watch the cradle movement. See if it returns to where you left it. Measure the clearances again. Cycle the brakes several times while watching everything that moves - pad cradle, air cylinder stroke, etc., etc..
Hopefully we’re not talking thousands of an inch movement and you will be able to see variances by eye.
But then maybe not.

On the warped rotor you would think you would get some oscillation in the pedal. I have none.

No leaky air chambers. Our test was hook external compressed air to the coach with no engine running. Applied service brakes and released many times , held foot on brake , no air leaks. applied parking brake no leaks.

The spring kit he talks of I am looking into although I believe it springs the caliper back to static and has nothing to do with the air chamber.

These calipers are adjusted by turning an adjustment shaft until the pads seat with the rotor then specs say back it off 3/4 turn. We have been at 3/4 turn with some heat and 1/4 turn with excessive heat. Advice from a truck mechanic suggested trying 1 and 1/2 turns and measuring the temperature to see if we are chasing a tight brake adjustment.

We are also looking into grease inside the caliper as Meritor describes purging the old grease out (which we thought we did) but if for some reason the caliper still has grease inside and is hydraulic lock could be reason for lack of proper return.

We have cycled everything we can think of with Right Rear Tires and Wheels off and the Coach aired up. Everything seems to work fine. We can move the rotor back and forth by hand when brakes are not applied and when applied we cant. We can move the hub and rotor again freely when no brakes are applied.


We will keep digging. Thanks for asking me these questions as it does help us rethink everything.

joe

[153stars]

You can put a magnetic mount and dial indicator to test run out.
Also call around to see if truck place will still turn a rotor or at least put it on lathe to check it for you. I don't think you'll get any feed back on pedal with air brakes.

[lowellhett]

When you changed pads, was there plenty of room to slide the pads into the caliper? I a not familiar with rear disc brakes. Is it possible air is leaking out causing that side to go into parking brake mode?

[joeplazek]

Originally Posted by lowellhett

When you changed pads, was there plenty of room to slide the pads into the caliper? I a not familiar with rear disc brakes. Is it possible air is leaking out causing that side to go into parking brake mode?

I did lay under it last night and looked it over real well. Had someone apply the brake and release while i turned the hub (as well as you can with axle in). The only thing I came up with is that after the brakes were applied and I manually backed the caliper off I couldn't push the inside pad back from the rotor. There is enough surface rust there that I had to tap the pad back with a punch and hammer. So out came the wire wheel on the Dewalt and I cleaned the inside of the caliper out and anywhere the pads made contact with the caliper. its the only thing I can say is a possibility. We have no air leaks.


joe

[MrMark52]

If the rust was surface rust that all calipers get after sitting for a few days without use, I’m thinking that isn’t the problem.

But that the inside pad continued to rub such that you had to use the persuader to get it to move sounds interesting.

I’m going to go back to Wolfe10’s advice, get the upgrade kit. While I find it hard to believe the design is such that the pad doesn’t back away sufficiently, may be that’s the problem. (?).

[CrownRoyale]

I just replaced the rotors and pads and axle seals on my 95 Monaco. Same setup you have. The previous owner did not do brake caliper maintenance and the brakes were dragging and causing excessive heat which cracked the rotors and wore the pads out.

This video is old and kind of funny for today's standards however it's got some very good information...

https://youtu.be/7N-St4Px8cs

[joeplazek]

Originally Posted by CrownRoyale

I just replaced the rotors and pads and axle seals on my 95 Monaco. Same setup you have. The previous owner did not do brake caliper maintenance and the brakes were dragging and causing excessive heat which cracked the rotors and wore the pads out.

This video is old and kind of funny for today's standards however it's got some very good information...

https://youtu.be/7N-St4Px8cs

Thanks.


joe

[MrMark52]

Just FWIW - there are several YouTube videos on Meritor Air Disc Brake Pad inspection and replacement. I watched the one from Meritor - the guy is pretty thorough on the why’s and wherefor’s of the procedures

Might be worth a refresher to see if there is something you might be missing.

[joeplazek]

Originally Posted by CrownRoyale

I just replaced the rotors and pads and axle seals on my 95 Monaco. Same setup you have. The previous owner did not do brake caliper maintenance and the brakes were dragging and causing excessive heat which cracked the rotors and wore the pads out.

This video is old and kind of funny for today's standards however it's got some very good information...

https://youtu.be/7N-St4Px8cs

Is your Monaco single axle or tag axle also?

joe

[joeplazek]

Originally Posted by MrMark52

Just FWIW - there are several YouTube videos on Meritor Air Disc Brake Pad inspection and replacement. I watched the one from Meritor - the guy is pretty thorough on the why’s and wherefor’s of the procedures

Might be worth a refresher to see if there is something you might be missing.

I have watched this 3 times. We are doing everything by the book. Thats why I am looking at other variables.

joe

[joeplazek]

Originally Posted by MrMark52

If the rust was surface rust that all calipers get after sitting for a few days without use, I’m thinking that isn’t the problem.

But that the inside pad continued to rub such that you had to use the persuader to get it to move sounds interesting.

I’m going to go back to Wolfe10’s advice, get the upgrade kit. While I find it hard to believe the design is such that the pad doesn’t back away sufficiently, may be that’s the problem. (?).

This corrosion was years sitting. Its all cleaned out now. Fingers crossed.

joe