Van Brake problem

Submitted: Wednesday, Apr 27, 2016 at 19:05
ThreadID: 132249 Views:2271 Replies:2 FollowUps:3
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I have had a strange brake problem with one brake on my van over the last few days. I always check the tyre temps, bearing temps and brake drum temps with my hand. One brake drum on the lead axle was hot and grabbing when I pulled up at Peak Hill. It was really nice of the van park owner and a worker who lent me a vehicle stand and brake adjuster. The wheel was tight to turn so I backed off the brakes and it just didn't gel how much I had to back it off and then how much I had to bring it back to the same position again. Having done this I pulled the drum off and found no problems at all so I reassembled and re adjusted the brakes.

Pulling into Temora I checked the brake again and the drum was hot so I went and saw Stimos auto repairs. The brake drum was hot and he was as baffled as me after running the normal checks.

I said if you can if you find one it may be best to replace the brake magnet, because I don't know where to go from here.

Well he got one and replaced it and the problem was gone.

I have no idea why this occurred or what caused it. The magnet had no residual magnetism, the controller was working fine and the brake was adjustment was all good.

Guess I will just have to put this down to f nose.
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Reply By: Malcom M - Thursday, Apr 28, 2016 at 08:28

Thursday, Apr 28, 2016 at 08:28
Does your brake controller provide any feedback about current going to the magnets?
Interesting to know if the magnet was being energised or just just springing out.
AnswerID: 599260

Follow Up By: 9900Eagle - Thursday, Apr 28, 2016 at 09:28

Thursday, Apr 28, 2016 at 09:28
Malcom, It is a P3 and it showed 00 on the screen when deactivated. The rear axle brake on that side was actually coming on marginally before the crook one.

The voltage climbed constantly with the use of the emergency brake activator and the proportional system is working ok.

The magnet looked good and was free on the spindle but once changed all was good. I have no idea as to why and I have read of others that have had a similar problem. The biggest problem was once it was fixed, there was no feed back.

This is actually why I posted, as it may or may not help others and thanks for asking for the extra information as that may help others as well.

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FollowupID: 868467

Follow Up By: Malcom M - Thursday, Apr 28, 2016 at 10:05

Thursday, Apr 28, 2016 at 10:05
The 00 is the voltage that the P3 thinks its pumping out but not necessarily related to what current the magnets are pulling such as might occur if you had a wiring problem. From memory there is a test menu in the P3 where you can see the actual current being pulled from the P3. It would have been interesting to see if the magnets were pulling current when they shouldn't be.

Are these 'off road' magnets or the standard blacktop versions? Quite a difference between them. The off road ones are constantly pushed onto the drums whereas the on road ones are held in place back from the drums.
Its possible that you were using on road magnets and one had a short circuit between the internal wiring and its metal case so that when it hit the drum (corrugations could do it) it completed the circuit and pulled power hence sucked onto the drum creating friction/heat...

You'll only know for sure by reinstalling the old units and monitor whats going on with a multimeter however if you do have a multimeter and still have the old magnets, measure the resistance of the two coils and see if there;'s any appreciable difference between them. Also the resistance of both wires measured to the case.

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FollowupID: 868471

Follow Up By: 9900Eagle - Thursday, Apr 28, 2016 at 12:21

Thursday, Apr 28, 2016 at 12:21
Magnets are on road ones and we replaced it with the same on road magnet.

With the van jacked up on that side you could rotate both tyres and when the brake is applied both would stop and when the brake was released both rotated freely with the new magnet fitted.

I only relayed the voltage, because to me if you don't have voltage you don't have current.

At Peak Hill with the van disconnected the brake was still binding and as said before it was not adjusting properly. When I pulled the drum there was nothing abnormal and after replacing/adjusting it all was good until I checked down the track. The retainer clip on the magnet was in place also.

I will keep checking the brakes and see what happens.

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FollowupID: 868476

Reply By: Member - graeme W (WA) - Monday, May 02, 2016 at 22:33

Monday, May 02, 2016 at 22:33
Hi. Exactly the same thing happened on our coromal van last year. Ended up removing the pads etc ( only option where we were) . Never found an answer or reason and have had no issues after fitting a new backing plate shoes and magnet. Even after disconnecting the trailer plug , hand brake and backing off the shoes as far as possible they were still coming on.There is a post on here june last year about it.
Cheers Graeme.
AnswerID: 599451

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