One brake overheating

[richinny]

i came across a brake issue today that i though was worth posting here. i tried a search but came back with too many results. in over 5 years of reading posts i don't recall seeing this problem.

a neighbor was working on a car trailer with electric brakes that had one wheel overheating. a new loaded backing plate was installed with the same issues. when the power was applied a tool would stick to the magnet and when the power was removed the tool stayed stuck to the magnet. the wires were removed from the magnet and the tool was still stuck to the magnet. it was easy to remove the tool but it was stuck firmly enough to defy gravity, lol.

a jumper wire was run from the backing plate to the frame with no change but after a jumper wire was run from the tow vehicle to the car trailer frame the tool dropped off.

[ROBERT CROSS]

Many years ago an old-timer advised when diagnosing electrickle.....ck the ground's furst.

Bob

[perryg114]

Why was this only on one wheel? I am having problems with one or more brakes overheating. The overheating wheel also tends to be the first one to lock up.

Perry

[HowieE]

Originally Posted by perryg114

Why was this only on one wheel? I am having problems with one or more brakes overheating. The overheating wheel also tends to be the first one to lock up.

Perry

Perry

To address your problem I would first suggest you jack up each side of the trailer and test the brake adjustments first, then the bearing free play. Overheating is not always a function of the brakes but sometimes a tight bearing can cause heat and in turn change things.

[HowieE]

When grounds fail then tend to produce an Open Circuit and an open circuit would result in less electromagnet force. Now that said that would hold true if the failed ground was at the fixture in question, the backer plate. You comment that when the car and trailer frames were connected the problem stopped leads me to thing the path to ground for that backer plate was some how other than that of the other brakes, back through the lighting circuits. Were any of the trailer lights on during this?

I would open the connection between the car and trailer and run wires across that connection to the trailer only from the brake power line and ground and then apply the brakes via the controller. Check the results at all the brakes.
If this works I would say you ave a crossed wire between the brake circuit and one of the lighting circuits.

I make these comments completely discounting your comment that the tool still stuck to the magnet after ALL WIRES were removed from the magnet. I can't invision any way the magnet, a completely floating item could have retained magnetism under that condition.

[perryg114]

It is not the bearings. When I back way off the adjusters the problems goes away. I don't like that adjusting brakes is trial and error. I may need new backing plates that release properly. My old ones may not be returning properly.

On the other guys problems, it is possible for steel to become permanantly magnitized in the presense of strong magnetic fields and this maybe my problem as well. It is also possible that the tool got magnetized.

Perry

Originally Posted by HowieE

Perry

To address your problem I would first suggest you jack up each side of the trailer and test the brake adjustments first, then the bearing free play. Overheating is not always a function of the brakes but sometimes a tight bearing can cause heat and in turn change things.

[HowieE]

Perry

The backer plate in question. How many springs are there connected to the shoes? I have seen this problem with plates that only have a single spring crossing between the 2 shoes. To the extent that one would have to back up to release the trailing shoe. Plates with 2 springs connected to the anchor pin are more effective.

[perryg114]

All the springs are there. I have been replacing brakes since I was about 10. I think for some reason mine are not releasing properly.

Perry

[TG Twinkie]

I don't think the problem is electrical in your case. A few questions.
How old are the brake assemblies?
Can you determine how much the drum and shoes are worn?
Does the brake mechanism move freely?
Are you sure the shoes are the correct ones for your trailer?
Is there a difference in the size of the front and rear brake shoes? If so. Are the shoes reversed by chance? The shorter shoe normally goes on the front.
If the shoes and/or drums are badly worn even adjusting won't help. If worn beyond specs and you adjust them using the normal procedure they could "cam over" and lock up.
If the brake releases when you back up, I would guess the problem is either with a binding mechanism or camming over is your problem.
Are the magnets in good shape?

[Aerowood]

Check the opposite side. Sometimes the one that is overheating is the side that is doing all the work and everybody assumes that it is the bad side when the opposite is the problem.

[perryg114]

The problem is the brake stays on a little bit all the time. This happens going down the road not stop and go. The first time it happened was on the maiden voyge. I was getting really bad gas miliage. When I stopped at the first rest stop one wheel was really hot. I jacked the trailer up and backed way off the adjuster and it was ok but wanted to lock up. Later I found that it got so hot it blew a grease seal. When I got back, I replaced the seal and put in new shoes. The next trip a wheel on the other side was doing the same thing. You can tell something is up because right before you stop it starts squeeling. The funny thing is it is the drum that I had turned on each side was was acting up. I deglazed the two that I did not turn. I have never had such trouble with hydraulic drum brakes. Normally I adjust them till it won't turn and then back off till there is slight drag. When I do this, one or more of them overheat just rolling down the road. Both the upper and lower springs are installed and the short shoe is on the front. I did have this sort of problem on the back of my Ranger truck and it turns out the brake compound was too aggressive and the brakes would lock with very little effort. The problem is all this stuff is made overseas with little or no quality control. Drum brakes are very sensitive. The front shoe is usually smaller and sometime of a different compound than the rear shoe. The reason for this is to control how much braking effort you get when the front shoe hits the surface of the drum. The friction from the shoe hitting the drum actually pushes it into the drum increasing braking force. I could also have weak springs or too much friction in the mechanism. I could also be getting too much drag of the magnet on the drum when there is no current through the magnet. I think new backing plates and getting all drums turned at the same time would be wise. I was under a time crunch when I did this. I was also trying not to brake the bank.

Perry

[richinny]

a few misc. comments on all the great replies.....

i can't think why the disconnected magnet would stay energized unless there is something in the internals that could do that.

i also think that the issue is in the ground line to the magnet that stays energized. i'll pass on the info about the cross wiring possibility. if there is a problem with one wire there may be more issues. also, i noticed on the dexter site that they recomment a common ground wire for all magnets. i don't know why.

we tried a few different tools to verify that it was not an issue of the tool holding residual magnetism.

perry, did you lubricate the shoes where they sit on the backing plate? sometimes they can wear a ridge and cause the shoes to not fully retract. since the brakes were heated enough to blow the seal could you now be having a problem with a spring that has lost some tension?

try testing to see if that magnet is staying energized like the one i saw.

one the hot brake being the only one working..... that should show up as the inactive brake staying in a 'like new condition' with no sign of heat coloring :-)

[TG Twinkie]

Like with your Ranger truck I had problems with my Dodge truck. The rear (drum) brakes would lock up with the slightest pressure on the brake pedal. I had to back up to get them to release. I bought this truck with 76K miles on it from a friend that bought it new. Turns out he rarely backed up or applied the brakes while backing up and neither did I. Therefore the so called auto adjuster was never or rarely engaged. After adjusting the brakes the old fashioned way 2 years ago and periodically backing up while intentionally pumping the brakes I've never had a problem.
While I know this won't apply to the trailer it may help others who have similar problems with their TV's.
You don't suppose the brakes got so hot that the return springs or other moving parts were damaged? Can you determine by the wear pattern on the shoes if you are getting the right contact with the drums? How do you know when the drums have been turned beyond specs? When you adjust the brakes in the conventional manner. If you back them off just to the point where they don't rub at all. Does that make any difference? Is there a grove worn in the area of the drum that the magnet could be hanging up in?
Just trying to throw a few things out here.

[perryg114]

We checked the drums with a caliper. The shoes had not fully seated yet in one trip to FL (1000mi). I have noticed that the new shoes only had about 1/8" of friction material on them. If the manufactures cheap out and don't put enough material on the shoes they will never fully seat in (diameters don't match). I don't think they got hot enough to de-temper the springs. I did not grease anything but the adjusters. Maybe that is part of the problem. With hydraulic brakes there is not much to lube. Lube can be a problem if it gets on the shoes. I think I will get some new backing plates and maybe a couple new drums to replace ones that are getting close to being out of spec. I also need to get self adjusting backing plates so I know all of them are adjusted the same. I don't think I will be going very far from home with the price of gas the way it is. I expect that we will take the wife's car to FL this fall to visit the folks when gas is $5/gal.

Perry