Electric brakes overheating-maybe. Ideas please

Submitted: Saturday, Mar 03, 2012 at 15:22
ThreadID: 92265 Views:16854 Replies:8 FollowUps:9
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I have some experience with electric brakes on a Tvan for a few years incl trips to Cape York,etc. I run a 100 Series TD Cruiser with a Prodigy Controller.
No problems whatsoever over the years with the TVan.

I have now swapped to a used Trakmaster Nullabor Van,dual axle, with I believe Alko electric brake system. I run the Prodigy on Boost 2 to give some braking oomph on the 2 ton van.
The van is 11 years old but one thing that was done not long before I purchased it was a complete brake overhaul incl drum machining,etc. The wiring and magnets look OK and of course the drums and shoes are good after the service.

After buying the Trakmaster,I did a brief inspection on the brakes and bearings to make sure all wiring,bearings and brakes looked in order and I set up the Prodigy as prescribed for a large towing weight. Also adjusted the brake shoes by locking up the drums and then backing off 4-6 notches to get free wheel spin - this adjusts the handbrake too. I'm not sure if this is the right adjustment if you have electric brakes + a handbrake function?
My problem is that on my first trip out,I found a drum overheating at a rest stop in Cann Rvr(Vic). I jacked up the van and backed off the shoes a bit and there were no further probs. All other wheels Ok for this trip.
I religously check for overheating at all rest stops when pulling the boat or the van - an old habit.

Yesterday,on the way back from Tuross Hd to Lakes Entrance,Vic,I had two stops and checked hubs both times - no probs. On the 3rd stop - at Cann Rvr again,I got a badly blistered hand from one hub - another was also hot but not
overly so.
I jacked up the van and backed off the shoes on both wheels and no more probs over the last 175km.
Obviously the shoes are(sometimes) not retracting properly after brake application - not sure if it's electrical or mechanical....AND,it has been a different wheel every time. I now have three wheels backed off and the braking effectiveness is now compromised.
I can't understand why I can travel 800km in the past week with no issues and when 200km from home,a problem suddenly develops.
Appreciate if anyone can give me input from experience as to what might be the cause before I start pulling things apart
Could it be the shoe return springs arew weak?
Could it be a problem with the Prodigy not handling 4 wheels ?
Why is it only happening sometimes?
Rgds
Ron
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Reply By: MEMBER - Darian, SA - Saturday, Mar 03, 2012 at 16:55

Saturday, Mar 03, 2012 at 16:55
G'day Ron - snap ! I'm towing a 09 Nullabor with a 100 TD also - I found early, as you have, that van brakes seem to be a moving feast - checking and adjustment is more frequent than I expected (but this is my first van). That said, I would expect to make a tweak here and there early in a 10 week trip and then not have to do any more until I get home. I take the shoes on until I get an even scrape then back them off about 12 clicks at least (pays to pull the shoes on manually, in between each adjustment). As for hub heat - the bearings can run hot if too tight (centre boss heat - cool drum)....after bearing services, it is common to have to back a castle nut off a bit - I once fixed a hot centre hub with only half a flat off on the castle ! My bakes were best when the van was new (funny that) - while the shoes still have about 4mm of meat on them, they don't bite as well as they used to (not helped by over greasing of the hub last year during a complimentary service :-o(.... but they are contributing to overall rig braking, which is enough for now. Drop me a MM if I can help with any TM info - I'm a also a TM club member.
AnswerID: 479294

Reply By: PeterInSa - Saturday, Mar 03, 2012 at 17:00

Saturday, Mar 03, 2012 at 17:00
Ron,
I previously had a brake controller that had a manual overide, this hand control once got stuck and If I had not noticed the drag with the brakes partly on could have caused problems.

Would also check the vans hand brake cable, may be grabbing somewhere

I personally would also borrow/buy another similar brake controller and try it, may be a less costly exercise than replaced brakes/drums on the van or worse.

Peter
AnswerID: 479295

Reply By: Ross M - Saturday, Mar 03, 2012 at 17:38

Saturday, Mar 03, 2012 at 17:38
G'day Ron B
Has the brake problem occured when you have been travelling with lights on or off.
Yes it could be the hubs are too tight on the bearings and that can cause the heating up. It is unlikely the adjustment will have to be backed off if correctly adjusted.
The brake may hang on slightly sometimes because of the mechanism of the brakes actuating lever being dirty or sticky in under the drum.

If all ran well and suddenly heating with lights on I would suspect the earths for the lights is sus and causing a small current to be flowing in reverse from the park light globe earth and this raising the voltage at the rear of the brake light switch on the output side and this will be trying to slightly turn on your brakes, hence the heating.
Check all earth connections to all lights and the trailer plug earth. The trailer plug earth is the most important one. Any earth point not correct will cause a voltage level to apear somewhere else in the vehicles brake and lighting circuits.
Probably not a hub or a brake problem but a wiring/earth problem.
AnswerID: 479296

Follow Up By: Member - Ron B (VIC) - Saturday, Mar 03, 2012 at 17:59

Saturday, Mar 03, 2012 at 17:59
Hi guys,
thanks for the fast replies.
I should make clear that after 45 years experience with bearings,it is NOT the bearings causing the problem. The Trakmaster has dual axles and parallel ford bearings and even if incorrectly adjusted a little,the load is well spread and the bearings can take a lot of abuse. The bearings are fine.
Since posting,I have also checked other sites such as "Caravanner's Forum" and there was some interesting stuff there.
Seems there are two schools of thought re how to adjust the brakes mechanically - one lot says do the "usual" as you would for drum brakes on a car and the other says use the "Alko method" and back them off 12-15 notches, as this is necessary to give the magnet/lever enough travel to create the correct mechanical force to properly activate the brakes - either way,I am not short of braking effort,in fact I have too much ...at times!
I will certainly take up Ross's suggestion to check the earths as I have not been happy with the park light earthing since purchase - it's an old van and the caravan aluminium sheeting and body is used to earth the lights (don't aks me about resulting electrolysis in this post!).
However,if there is a poor earth,I thought this would affect all brakes,not just the random wheels trip to trip?
and to answer Ross's question,the lights were off the first trip and probably on during most of the second trip - but the park ights had been on all day in the rain yesterday and at two previous stops yesterday the brakes were fine.
So sometime in the second half of the trip yesterday I applied the brakes and the shoes didn't retract properly - on two wheels only.
I will go over the system top to bottom starting with electrical connections and earths as a first step. The park brake cable is free running and OK.
The telling thing though is on checking overheating wheels,the shoes have been rubbing a little too much each time (and that's not how I adjusted them).
Any further thoughts appreciated
Thanks
Ron
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FollowupID: 754743

Reply By: Member - Toyocrusa (NSW) - Saturday, Mar 03, 2012 at 20:51

Saturday, Mar 03, 2012 at 20:51
Hi Ron. My brother has travelled over 10000Km in the last 6mths towing a Baroma van with 12 inch drums. We did drum machining,new shoes, cleaned and repacked wheel bearings and fitted new seals. The Cruiser has a Prodigy P3. It ran trouble free until a few days ago down in Vic. he found one drum getting hot. Backed off the adjustment but it still ran hot so he disconnected the wiring to that wheel and travelled the last few hundred K without any problem. It does seem like some sort of residual current but as yet we have been unable to work it out either. Voltage test at the car plug was OK at the time of testing so like you, we are at a loss to explain it. Cheers,Bob.
AnswerID: 479332

Follow Up By: Ross M - Saturday, Mar 03, 2012 at 23:13

Saturday, Mar 03, 2012 at 23:13
When you tested the voltages at the plug did you check it with the plug half apart and with it also plugged into the vehicle at the time of checking?????
Cos if you didn't it wasn't checked "in situ" so to speak.
Just the normal checks aren't picking up where the faults are.

If you back off the brakes to any degree you will have a situation where the magnet gets a, run up, when it is energised and not just pull into the braking action but it will apply with a rush and somewhat uncontrolled.
Also if the adjustment is slack, these SERVO TYPE brakes will wrap on and tend to lock on and remain on. They rely on the brake magnet initiating the action but its effect is magnified by the servo wrap on action of the design.

Just another possibility, the van might have solar and the charging of the solar is feeding into the caravan circuits by poor earth action and causing some degree of brake action.
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FollowupID: 754793

Follow Up By: Ross M - Saturday, Mar 03, 2012 at 23:16

Saturday, Mar 03, 2012 at 23:16
When you tested the voltages at the plug did you check it with the plug half apart and with it also plugged into the vehicle at the time of checking?????
Cos if you didn't it wasn't checked "in situ" so to speak.
Just the normal checks aren't picking up where the faults are.

If you back off the brakes to any degree you will have a situation where the magnet gets a, run up, when it is energised and not just pull into the braking action but it will apply with a rush and somewhat uncontrolled.
Also if the adjustment is slack, these SERVO TYPE brakes will wrap on and tend to lock on and remain on. They rely on the brake magnet initiating the action but its effect is magnified by the servo wrap on action of the design.

Just another possibility, the van might have solar and the charging of the solar is feeding into the caravan circuits by poor earth action and causing some degree of brake action. After water and moisture effects on earths electricity always find the shortest path.
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FollowupID: 754795

Follow Up By: Member - Ron B (VIC) - Sunday, Mar 04, 2012 at 10:30

Sunday, Mar 04, 2012 at 10:30
Hi Bob,
your brother's braking troubles were in Vic??
Wasn't in Cann Rvr was it?? - that seems to be where I'm having troubles - twice now in the same place.
Seriously though,it is time for a complete overhaul and inspection on my braking system. I don't want tyre and bearing failures in the outback due to overheating on my 12month big trip within the next year or so.
I won't be happy until I've inspected everything and checked for proper function.
We were washed out of Southern NSW on Friday cutting a 4 week trip to 4 days and I've got a couple of months before the next trip - it'lll take that long for all the rivers to settle again,so I will start taking it all apart next week.
Rgds
Ron
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FollowupID: 754830

Follow Up By: Ross M - Sunday, Mar 04, 2012 at 12:16

Sunday, Mar 04, 2012 at 12:16
Sorry about the stutter folks, I don't know what happened there.
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FollowupID: 754867

Follow Up By: Member - Toyocrusa (NSW) - Sunday, Mar 04, 2012 at 19:32

Sunday, Mar 04, 2012 at 19:32
Thanks Ross and Ron. Pretty sure he was down around Bairnsdale when it happened and like you, because of the weather made a run for it up to Shellharbour. Doing a GVM upgrade on the Cruiser this week so will concentrate on the van next week. The van does have Solar but hasen't been a problem over 3 preceeding years.(They are on the road full time) Thats not to say it isn't now so thanks for the tip. Cheers,Bob.

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FollowupID: 754941

Reply By: Mechdave - Sunday, Mar 04, 2012 at 20:22

Sunday, Mar 04, 2012 at 20:22
G'day Ron,
Are your van brakes fitted with automatic adjusters that click up the adjustment over several brake applications? This would explain why they don't overheat until several hundred km's down the road.
Another thing to check is to make sure the trailer brakes aren't coming on too hard. Usually there is an adjustment knob on the side of your controller to adjust for the weight of your trailer. The way I have always calibrated the controller is to wind off the braking effort on the controller and whilst braking moderately increase the braking effort on the trailer until you feel the trailer stop pushing you. This is when the trailer is braking its own weight but the brakes are not working too hard and pulling up your vehicle as well.

As far as adjustment of the brake friction material, the correct way has always been adjust the wheel brake until it locks and then back off 4 or so clicks until the wheel spins freely again. With a handbrake make sure when you adjust it that you don't adjust it too tight, all it needs to do is stop the trailer from rolling away whilst disconnected.

Electrically it is doubtful that your lights are finding an alternate earth path through the braking system. Although you may need an earth strap to go from each axle to the chassis somewhere if you are concerned about earth problems. Here is a generic wiring diagram to help --> Generic trailer brake wiring diagram

If your trailer draws too much current for your brake controller it may not work correctly, it might blow fuses or overheat your controller. I suggest you confirm your controller will run tandem axles if you are unsure.

I recommend you first check your handbrake adjustment as this is the most common problem for overheated brakes.

I hope all this helps,

Chers,
Mechdave :)
AnswerID: 479469

Follow Up By: Member - Ron B (VIC) - Sunday, Mar 04, 2012 at 23:23

Sunday, Mar 04, 2012 at 23:23
Hi Dave,
thanks for the follow up. I don't have auto adjusters so that's not the issue. I'm running a Tekonsha Prodigy P2 controller for the caravan and have previously used it extensively pulling a 1 ton off-road camper trailer through some of the roughest terrain in Oz - so it's not new technology to me.
The Prodigy has no problem with dual axles either.
The caravan braking was set up as per Tekonsha specs when I first got the van ,ie adjust the shoe clearance (same as per your recommendation),warm up the brakes and then set the controller so when braking,you can "just" begin to feel the effect of the van braking pulling on the tow vehicle. In addition,I followed the boost setting recommendations for my trailer weight and after using B1 for a while,I have upped it to B2 - that sends a bit more current to the brakes when they're applied - takes a bit of effort to pull up a 2 ton+ van.
I'm very familiar with general trailer wiring and have checked it all and also the internal caravan wiring. As mentioned though,I am concerned about earthing in general throughout the van and I will now fully check that - thanks for those great diagrams by the way which I'll print and use for reference. I am also fairly certain it is not happening because of some spurious current path throught the magnets (due to bad earthing).
As the overheating problem has occured randomly now on 3 of the 4 wheels and in each case,I have found the shoes rubbing too much,and had to back them off to clear the problem,it is fairly clear the brakes are being applied and then not retracting properly - this is either a mechanical issue with sticking parts or weak springs,OR,there is still current there holding the shoes on the drums. However,when current is applied to the magnets in my hubs,there is a very audible "buzz" while the tow vehicle brake pedal is depressed and I assume this is the magnets working against the drums.
There has been NO audible indication of current in the brakes though on the overheated drums when I've checked them.
Lastly,there is plenty slack in my handbrake cable so it's not that.
I'll work through it all in the next couple of weeks as it needs to be fixed as my brake shoes are backed off to the point that braking is compromised
Rgds
Ron
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FollowupID: 754970

Reply By: peterb1 - Tuesday, Mar 06, 2012 at 20:19

Tuesday, Mar 06, 2012 at 20:19
check return springs on shoes,back off hand brake when adjusting shoes,then adjust handbrake cable with trailer loaded and level as cable can get tighter as suspension moves,you should only need to back off shoes two clicks if shoes are seated properly and drums are round ,try unplugging brake controller to determine if it is electrical or mechanical,
AnswerID: 479664

Follow Up By: Member - Ron B (VIC) - Wednesday, Mar 07, 2012 at 09:56

Wednesday, Mar 07, 2012 at 09:56
Thanks mate,some useful suggestions which I'll follow up
Rgds
Ron
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FollowupID: 755170

Reply By: garthyguts - Wednesday, Mar 07, 2012 at 10:42

Wednesday, Mar 07, 2012 at 10:42
try to centre the backing plate first, loosen the four nuts on the plates adjust brakes to lock up. re tighten nuts and back off brakes 10 clicks( i worked for alko)
try that
AnswerID: 479736

Follow Up By: Member - Ron B (VIC) - Wednesday, Mar 07, 2012 at 11:20

Wednesday, Mar 07, 2012 at 11:20
Thanks mate,that's a good suggestion. These brakes were supposed to fully serviced not long before I bought the van with drums machined,etc.
It is possible the backing plates were removed and re-fitted slightly off centre.
Wouldn't take much to cause problems.
Rgds
Ron
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FollowupID: 755175

Reply By: Member - Ron B (VIC) - Sunday, Mar 11, 2012 at 13:41

Sunday, Mar 11, 2012 at 13:41
Hi all,
firstly many thanks to all who contributed with suggestions. I have made some progress and although I have not finally solved the problem,I am fairly sure it is electrical...specifically earthing issues.

Progress so far:
-I have disassembled the hub of the worst wheel that gave me the blisters on the hand from being so hot.
- bearing grease was well burnt BUT,bearings and stub axle were fine(thankfully),seal not so good as you might imagine(I will replace the bearings).
- drums have some uneveness but look to have been machined not too long ago and in my view they are very serviceable.
- magnet looks fairly evenly worn and has plenty life left with all wear holes visible and 2-3mm left all round.
- return springs seem fine as is the brake assembly which is free moving.
- handbrake actuator also OK.
- shoes look evenly worn and apart from the bottom of one shoe which has 3.5mm -4mm,they have 4-5mm left all round.

From the above I am assuming it is NOT a mechanical issue.

So as per a suggestion in this thread,AND on advice of a local ALKO agent I found,I began a full trace of the electrics. I cannot get inside the subframe where most wiring is but I have fairly confidently deduced:

- the wiring loom from the trailer plug enters the subframe and re-appears at the rear interior of the caravan and is terminated at a fuse panel with the exception of the EARTH wire. The blue service brake wire is fused with 15A.
(all OK so far).
- the blue serv brake wire then re-enters the subframe and supplies all 4 brake magnets (in parallel) - this is OK as it is a dedicated wire to the brakes.
- the earth wire from the car loom exits the subframe under the caravan and is terminated on the external rear chassis rail.
- I can find no other earthing arrangement for the wiring loom OR the brakes. The return (earth)wires from the brakes enter the subframe at the drivers side rear caravan wheel and go REARWARD,therefore i can only assume that in the subframe or behind some cupboard wall,the brake earth joins with the lighting earth(see above) and shares the same earth termination on the rear ext chassis!!!
- now as my van batteries,ext park,brake,clearance lamps,etc are all sharing a common earth which is either the subframe or the side alum cladding,I see significant potential for reverse current paths through the magnets (shortest path and all that).
- as mentioned previously,I have earth troubles sometimes with my clearance lights so there is a clear case here for a separate earth run from the brakes direct to the trailer plug.
-I also believe I had my clearance lamps on, on the day of the troubles due to significant rain

As mentioned,I found a local ALKO agent with many years experience. When he heard my problem,he asked - do you have an off road(poly block) coupling.When I replied in the affirmative,he said it was "electrical" and he was prepared to bet one part of his anatomy on it!!! (I asked if he had one to spare?). He indicated DEDICATED brake wiring to the tow vehicle plug has fixed these problems in EVERY instance he has seen over many years -and there have been many.
So next step is to just confirm today's analysis by taking my brake parts to the ALKO guy for inspection and confirmation that the mechanical side is OK.
If that goes as expected,I'll re-wire the brake earthing circuit direct to the plug.

Also inspect every hub,bearing and brake assembly to ensure all is OK.

If anyone has any ohter thoughts,please advise - all feedback most welcome.

Rgds
Ron



AnswerID: 480081

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