Unusual Brake Malfunction

[BTFT]

I had a very serious and unusual brake malfunction on the way here to Texas from Tucson. But the problem on this wheel started some time ago.


I arrived back in the states after 4 months of travel in Europe picked up my 34 ft TT in Maryland and started off for Tucson. I was trying to get thru DC traffic before rush hour. I pulled in to a gas station to fuel up and one of my trailer brakes was hot and smoking. The others were all cool...no problem.



I didnt want to take the time to remove the wheel and see what the problem was so I just adjusted the brake out so it wouldnt engage and went on.


Fast forward to Tucson: Yes I left the brake like that the whole trip with no problems and I didnt expect any.



But once in Tucson I pulled the wheel to inspect the brake and found the forward brake shoe had jumped off its cam at the top and that was what was dragging. I looked for any other problems and found none. I fixed it up repacked the wheel bearing and put the wheel back on (I have done this before)


On the way from Tucson To Texas I was passing thru Deming New Mexico and I got a trailer brake warning on my dash. I pulled over into a fuel stop and found the wheel extremely hot. The same wheel as above. So I pulled the wheel off and found that the magnet had melted itself and had scored the drum and heated the drum in one place until it was blue. The magnet was a melted mess.


At the stop right before Deming I did my usual walk around and nothing was amiss. (about 2 hours earlier)



To get going again I cut the brake wires to that wheel and tied them off so that the magnet would not try to engage. (Yes the rest of the brakes work just fine) Now that I am at a place where I can work on it I will replace that brake assembly.



Now for some background: These were all new brakes that I installed in Fairbanks AK the previous October. They are all high quality pre assembled/bolt on brakes. I have not had one minutes trouble from any other brake out of the four. These brakes had gone from Fairbanks to Maryland and Maryland to Tucson where I thought I had fixed the problem on that one wheel.


Brake linings are all good and plenty left. And this is the only brake problem I have had on this trailer in just over 67,000 miles of pulling this trailer since August of 2015. (2 sets of brakes)



So has anyone had a brake do this? If so what did you find out about what made it happen?

[Loydmeeks]

Last year we had the magnet rub the drum until it got so hot my dexter plug melted off and grease went everywhere. Being I am disabled I had to depend on an RV service tec. He installed new bearings, seals and magnet. Cost $ 525.00 to have him repair it on a Sunday

[PKI]

The brake was hot and components were quite likely damaged by that heat.

A shoe out of place suggests the original install was incorrect or the backing plate components were not correctly manufactured. Something allowed that shoe to move out of place and whatever that was is likely the root cause.

[BTFT]

Originally Posted by PKI

The brake was hot and components were quite likely damaged by that heat.

A shoe out of place suggests the original install was incorrect or the backing plate components were not correctly manufactured. Something allowed that shoe to move out of place and whatever that was is likely the root cause.

Actually as I said in my post the brakes came as an entire assembly that bolt to the axle. They are pre assembled. Also these brakes worked perfectly from Alaska to Maryland. For that reason I am discounting the "assembled incorrectly theory"



It seems to me the heat is the result of the problem not the cause...but as you say it is the cause of the melting of the magnet...but then one has to ask why did the magnet stay engaged long enough to get hot and melt?

[charliez]

why did the magnet stay engaged long enough to get hot and melt?



Because voltage was being applied to it when it was not supposed to be.

[BTFT]

Originally Posted by charliez

why did the magnet stay engaged long enough to get hot and melt?



Because voltage was being applied to it when it was not supposed to be.

If that was the case ALL of the brakes would hav engaged. This I would have felt and the rest of the 3 brakes would also be hot...that was not the case.


Please don't get me wrong I am not arguing but just discounting certain events through a process of elimination.


I cannot think of any case in which only one brake could get power/voltage and the others not when the wires are all connected together.


Now you are correct the magnet had to have stayed engaged on the drum for this to happen...Why and How is the question.


It could be that some part had broken off and fallen behind the magnet that stopped the magnet from disengaging...but I found no direct evidence of that when I opened the wheel.


This may remain a mystery...I am still hoping this has happened to someone else and I will hear from them.

[Brentw]

Odd that it worked previous, are you sure it was correctly assembled from the box? I recently replaced all the brakes on my enclosed trailer, tandem #3500 axles. I found one new assembly with the magnet actuating lever over one of the shoes. Visually it looked wrong so I caught it right away, and I'm not sure the drum would have fit over them.
Throwing you straws to grasp at.

[BTFT]

Originally Posted by Brentw

Odd that it worked previous, are you sure it was correctly assembled from the box? I recently replaced all the brakes on my enclosed trailer, tandem #3500 axles. I found one new assembly with the magnet actuating lever over one of the shoes. Visually it looked wrong so I caught it right away, and I'm not sure the drum would have fit over them.
Throwing you straws to grasp at.

Good question but it was a while ago but if I had noticed anything at the time I would have acted on it...my recollection is they were all the same and looked correct.


But again the fact it worked perfectly from Alaska to Maryland indicates to me it was ok and that this recent trouble is something new...


A broken part that would not let the magnet retract is my only guess so far. But then again I saw no evidence of that when I first opened the wheel. Of course I was not expecting anything like I found.


I will be taking the parts with me to a trailer supply place to get a new brake before I leave here.

But I was truly hoping that someone might have had this happen to them and joined in here.


Thanks for all the comments and Ideas from everyone.

[Barlow46]

Self adjusting feature malfunction possible?

[steve52]

Sounds like a factory assembly defect. I had a similar problem once years ago when a brake shoe retainer clip let go, and everything inside the hub got ruined.