You are not logged in or registered. Please login or register to use the full functionality of this board...
Newell Gurus
Hot Brake/Stuck Caliper? - Printable Version

+- Newell Gurus (https://newellgurus.com)
+-- Forum: Technical Discussions (https://newellgurus.com/forumdisplay.php?fid=3)
+--- Forum: Suspension/Tires/Wheels (https://newellgurus.com/forumdisplay.php?fid=5)
+--- Thread: Hot Brake/Stuck Caliper? (/showthread.php?tid=6188)

Pages: 1 2

Hot Brake/Stuck Caliper? - Richard - 07-14-2021

Something occurred to me late in the diagnostic procedure for a really hot brake incident, that I thought I would pass on. It sounds SO......simple, but in the heat (no puns) of the moment, it didn’t occur to me initially. If you suspect a dragging brake, jack the wheel up and turn by hand. Duh huh.

Here is what happened. Over the winter I did all the brakes, including new rotors on the front. I am pretty conscientious about using the jakes to hold the speed on a grade somewhat below the speed limit because that prevents the emergency braking system that sits in the passenger seat from activating. 

But just for grins on a long grade in Montana, I decided to see what slowing the coach down a long grade without the jakes would be like. So, I used the brakes a good bit. When we hit the bottom I smelled the characteristic hot brake smell. OK, no biggie I thought. But it continued for over ten miles until I could find a safe place to pull off. The left front brake was wisping smoke. And as I watched the wisp grew. To be safe, and not burn the coach to the ground, I gave it a shot from the fire extinguisher. Smoke went away. I cribbed the front, and crawled under. The caliper moved a bit when coerced by a long screwdriver. I wasn’t quite sure what was happening. The navigator said there is a truck pull off in two miles, so I decided to limp there for further detective work. We made it, and the brake was not smoking upon arrival nor was there any smell. I pulled the caliper pins with the 14mm hex tool, and both were slick, lubed, and showed no signs of seizing. They came out by hand. But I still was not sure if I had a problem or not. Then the bone simple idea hit me. Jack it up, and turn by hand. OK, no resistance from the brakes at all.

We have driven about 700 miles since then with plenty of brake application. I have checked the rotors with the IR gun at each rest stop and they read within a few degrees of one another which give me confidence that the problem was transient, although I will keep a close eye on it. 

Two things to note. One, the temp sensors in my TPMS did NOT show any difference from side to side while driving. However once stopped, the temp sensor showed a 50 degree increase on the sticking side after we sat on the side of the road for 20 minutes. I suppose it took some time for the heat to transfer from the disc to the wheel, through the stem, to the transmitter. Second, there was NO pull when taking hands off the wheel to indicate a stuck caliper on one side. There is also no pull when hard braking. 

I don’t know what happened and I wish I did. My speculation is that this was the first time the new brake pads had seen significant heat, and something came out of the brake pad and lodged itself against the rotor. I won’t be able to prove that until I take the tire off and pull the pads. Unless I have another issue, I won’t do that until I get home.

RE: Hot Brake/Stuck Caliper? - ccjohnson - 07-14-2021

Richard,
Have you thought about having a piece of road debris or gravel wedged behind the heated caliper? When cooled enough contraction sufficient to allow it to drop out and hide from you? My daughter had this happen to her car on a dirt road.

RE: Hot Brake/Stuck Caliper? - folivier - 07-15-2021

Clint a piece of debris would have probably caused some scoring on the rotor surface.
Richard do the brakes have a return spring for the calipers? On my FT and many others we have added that spring, not sure how similar our brakes are.

RE: Hot Brake/Stuck Caliper? - Richard - 10-14-2021

Well……..

We had another incident of the hot brakes coming down I 17 from Flagstaff into Tom’s Resort. This time, the first thing I did was jack up each front tire and check to see if the brakes were dragging. They were not. Hmmmmm. Conclusion being, something else is going on. I noticed both the drive drums and tag discs were not even warm, meaning all the braking was being done by the fronts. I wasn’t in a great place to do any more looking, the coach stopped just fine, and I decided to proceed although gearing down on the jakes to reduce my brake useage even more. The temps came down quickly, and we had no more problems. 

While at Tom’s, I lay awake at night thinking of all the things it could be, and how to check each one. 

Turned out, it was very simple. The picture is of a brass coupling in the pilot line from the brake pedal to the brake relay valve in the rear. It is cracked through and through. The impact of that crack is it reduced the signal pressure from the brake pedal to both the drive and tag brakes. I had Rhonda apply the brakes while I was under the rear, and immediately heard the air leak.
   

I had a gauge inserted into the M&G brake line to measure actual brake line pressure. With the crack, I got no more than 60 psi, after the repair the brake line pressure was at 90.


I have added the apply the brakes and listen for leaks to my safety check list.

RE: Hot Brake/Stuck Caliper? - Trainer - 10-14-2021

Richard, Do you have Meritor helper springs on each slide pin on each brake as suggested by Forest? They directly address moving the pads away from the rotor when not braking.

RE: Hot Brake/Stuck Caliper? - ccjohnson - 10-14-2021

Richard,
It seems while we were all looking for horses, you found a zebra!

RE: Hot Brake/Stuck Caliper? - bikestuff - 10-14-2021

That is an amazing find! I wonder how many other coaches are riding around with only some of the brakes not working?!

RE: Hot Brake/Stuck Caliper? - BusNit - 10-14-2021

Being a new to me coach owner thanks for this info. I may inspect my fittings. Where do you jack up the coach from? I need to figure out where to place my 20 ton bottle jacks along with where to you put your cribbing?

Thank you!

RE: Hot Brake/Stuck Caliper? - Richard - 10-14-2021

Rudy,

The fronts are Knorr Bremse so the caliper spring hack is not the same. The slide pins were removed and checked. Slick as glass. The wheels were rotated with no evidence of stuck caliper.


Simon, there are several posts on this site about appropriate jacking points and places to place jack stands/cribbing. If you can’t find them using the forum search engines, then let us know.

Bill, I think the reason it wasn’t evident I had a problem until extended downhills was the rears were working, just not as strongly as the fronts, because there were not getting the same pressure to the relay valves.

RE: Hot Brake/Stuck Caliper? - DK on the road - 10-15-2021

I am finding this post interesting.

I find my coach does not slow as good as other semi trucks or my previous MH. I always thought that, well, I'm 57,000 lbs, towing a full size pickup (but it has a braking system). This Newell is 2x's heavier than my last MH, and the Semi's were 5 and 7 axle trucks, so way may brake SQ inches.

I must extend my investigation now.