override brakes

Submitted: Tuesday, May 11, 2010 at 15:25
ThreadID: 78391 Views:3020 Replies:6 FollowUps:4
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Hi all.
I have recently bought a 1300kg Agg.caravan with override brakes and on several trips I have not felt the van brakes being applied and have not detected any movement in the application shaft moving in the housing against the spring.This was tested by applying masking tape to the shaft which would clearly show any braking movement.The braking mechanism has been stripped and serviced.the mechanical brake linings have been renewed ,wheel bearings are new and cables correctly adjusted.
Is ther anyone out there that might give me a clue as to why the brakes don't come on.Maybe I'm not braking hard enough.The brake mechanism has 2200kg stamped on it.Hope you can help.
regards kman
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Reply By: Member - Ian F (WA) - Tuesday, May 11, 2010 at 16:11

Tuesday, May 11, 2010 at 16:11
Hi kman1,
Have you checked that the tow hitch coupling can rotate when removed from the vehicle? It could be seized ie rust.
Ian
AnswerID: 416285

Follow Up By: kman1 - Wednesday, May 12, 2010 at 15:58

Wednesday, May 12, 2010 at 15:58
Hi Ian,the hitch coupling has been thoroughly cleaned and regreased.Absolutely free to move in any direction.
thanks kman
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FollowupID: 686525

Reply By: brushmarx - Tuesday, May 11, 2010 at 16:29

Tuesday, May 11, 2010 at 16:29
You could chock the caravan wheels, and try reversing. That should contract the hitch to see if it moves, as long as the reversing lever thingy is off.
Anything else exceeds my brainpower in this matter.
Cheers
I'll get there someday, or die wanting to.

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AnswerID: 416289

Follow Up By: kman1 - Wednesday, May 12, 2010 at 16:02

Wednesday, May 12, 2010 at 16:02
Hi Brushmarx,
Did exactly that and with considerable power the hitch did move and applied the brakes.Would appear the spring is to strong for the weight of the van.
thanks kman
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FollowupID: 686526

Reply By: 1970monaro - Tuesday, May 11, 2010 at 17:30

Tuesday, May 11, 2010 at 17:30
G day kman what happens when u reverse the caravan with the lock opened the brackes should lock up you could reverse up a hill and then stop to see if the shaft has moved .If they dont lock up in reverse and the shaft has moved with all the work that has been done the only thing left is air in the brake lines Good Luck
AnswerID: 416296

Follow Up By: kman1 - Wednesday, May 12, 2010 at 16:06

Wednesday, May 12, 2010 at 16:06
Hi 1970monaro,Have reversed up a slight incline without brakes applying.The brakes are mechanical (cable operated) so no brake lines.
thanks kman
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FollowupID: 686527

Reply By: Member - Brian R (WA) - Tuesday, May 11, 2010 at 19:11

Tuesday, May 11, 2010 at 19:11
yes i agree with previous posting ...and would bleed the system
brian
AnswerID: 416315

Reply By: Member - Ed C (QLD) - Tuesday, May 11, 2010 at 20:05

Tuesday, May 11, 2010 at 20:05
Well, you seem to have 'ticked all the boxes' (except one;-))

If there is nothing binding the shaft (or the spring) in the housing, then my guess is that the spring in the (2200kg rated) over-ride coupling is too heavy for the weight of the 'van, which is simply not heavy enough to compress the spring under normal braking...

I'd suggest trying a lighter rated spring, and see how ya go with that, or you may be able to have the existing one re-set to a 'progressive' rating...

(JMO)

:)

Confucius say.....
"He who lie underneath automobile with tool in hand,
....Not necessarily mechanic!!"

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AnswerID: 416322

Follow Up By: kman1 - Wednesday, May 12, 2010 at 16:19

Wednesday, May 12, 2010 at 16:19
Hi Ed C(QLD),Basically I had come to that conclusion except for the fact the van is a 1982 model and the coupling appears to be original because they don't make a 2270kg coupling anymore.I can't believe previous owners have towed the van all those years without effective brakes.Maybe the spring has work hardened and does'nt compress as easily as it did when new.To replace the coupling isn't a problem(about $100)but I could still be faced with the same issue.
The point where the shaft meets the contact plate seems to cause the handbrake to be forced horizontal rather than upwards to apply the brakes.
thanks kman
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FollowupID: 686530

Reply By: Nargun51 - Wednesday, May 12, 2010 at 17:44

Wednesday, May 12, 2010 at 17:44
I know the brakes are OK, but is the contact plate set the correct distance?

From my memory of over ride brakes the end of the braking shaft should sit just against or just shy of the hand brake contact pad.

The coupling shaft moves back when you back against the chocked van

If brakes don’t engage, the contact plate is too far away from the end of the coupling shaft or the pin that it rotates about is cactus. Just undo the locking bolt and adjust

If it doesn’t move the problem would lie within the coupling break unit itself; it would appear that either the shaft is rusted in place, the spring is U/S or has broken and jamming the shaft or there is a lot of crud in there. You may be able to rotate it, but it is blocked against fore/aft movement.

Again, my memory is vague, but I think that if you undo the coupling from the chassis access to the spring is from underneath the coupling…You may find 30 years of rust and dirt blocking the movement. WD 40 and grease could be your friends
AnswerID: 416426

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