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rear brakes locking up
https://www.ausmini.com/forums/viewtopic.php?f=2&t=49478
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Author:  monkey [ Thu Jan 22, 2009 2:19 pm ]
Post subject:  rear brakes locking up

Hey all
I have just replaced all the wheel cylinders and the master cylinder and now my rears lock up for about 10sec or so when i apply the brake.

i had a search and found that it could be the bias valve, is there any other reason/s why this could be happening before i go searching for a new/recon bias valve?

cheers James

Author:  Wombat [ Thu Jan 22, 2009 2:38 pm ]
Post subject: 

Did you fit the right size rear wheel cylinders?

Author:  monkey [ Thu Jan 22, 2009 2:58 pm ]
Post subject: 

fitted 3/4 on the rears and 15/16 on the fronts..
hope they are right - didn't know there was differnt sizes :oops:

Author:  Wombat [ Thu Jan 22, 2009 4:41 pm ]
Post subject: 

Somewhere Matt Read did a How To on turning the bias valve on the rear subframe into an adjustable one - Matt?????

Here is one way- think Matt did it different -

Author:  IndigoBlueCooperS [ Thu Jan 22, 2009 6:24 pm ]
Post subject: 

I had the same problem. Fitted a new bias valve with no change.
Then fitted new rear shoes and drums and the problem went away.
I suspect the rear brake shoes were not the correct size for the drums, although the adjustment was OK. Are your rear shoes on the correct way around?

Author:  monkey [ Thu Jan 22, 2009 7:21 pm ]
Post subject: 

i'm pretty sure i didn't have to remove the shoes on the rears to fit the new cylinders but heres a pic any way..
Image

james

Author:  1018cc [ Thu Jan 22, 2009 7:46 pm ]
Post subject: 

Why did you replace the rear wheel cylinders? If it was because the wheel cylinders were leaking, brake fluid on brake shoes make them more sticky and they lock when the brakes are applied.

Author:  simon k [ Thu Jan 22, 2009 10:15 pm ]
Post subject: 

IndigoBlueCooperS wrote:
I had the same problem. Fitted a new bias valve with no change.
Then fitted new rear shoes and drums and the problem went away.
I suspect the rear brake shoes were not the correct size for the drums, although the adjustment was OK. Are your rear shoes on the correct way around?


hey, good one Rob - glad you got that problem sorted

monkey, what do you mean by this bit?

Quote:
now my rears lock up for about 10sec or so when i apply the brake.

Author:  monkey [ Thu Jan 22, 2009 10:40 pm ]
Post subject: 

1018cc,
yeh i replaced them b'cos they were shot - no fluid was leaking but when i pulled the rubber back on the old cylinders there was a lot of rusty fluid that came out.. i'll give them a clean with some brake cleaner and see how they go.

simon,
when the car is up on stands n i apply the brakes then release them n try to turn the rear wheels by hand they will not budge, fronts are fine.
and i dont have the hand brake on :lol:
i also went for a test just up and down my drive way and after stopping then going agen its like the hand brake is on (rears wont rotate, just skid/slide) for a second or two then everything is normal untill i brake agen...


hope all of that makes sense :D

Author:  Dylans Clubby [ Thu Jan 22, 2009 11:25 pm ]
Post subject: 

sounds like they are sticky... maybe bleed the lines and see how you go?

Author:  baby_austin [ Fri Jan 23, 2009 12:30 am ]
Post subject: 

It could also be the flexible hoses cause if they are original they can collapse internally.

So to explain the prop pressure is applied pushed past the blockage and then takes several seconds to release pressure form the wheel cylinders.

Or
As others have said it could be the pressure regulator up the back.

Cheers
Matthew

Author:  monkey [ Fri Jan 23, 2009 6:21 am ]
Post subject: 

thanks guys i'll check out those things today.
is there anyway of checking to see if it is the bias valve? or is it just a matter of elimination and replacing it n hoping its the problem

Author:  simon k [ Fri Jan 23, 2009 10:38 am ]
Post subject: 

the fact that it's both wheels kinda points to the prop valve - I'd pull it apart and clean it out -

have you flushed the system - IE let all the fluid out, run half a litre of metho through it, and then fresh brake fluid - if there is a lot of gunk (rust, slime etc.) then things may be getting blocked

Author:  Wombat [ Fri Jan 23, 2009 3:17 pm ]
Post subject: 

Photo shows right assembly for right side drum - is the left side the mirror image?

Author:  simon k [ Fri Jan 23, 2009 3:38 pm ]
Post subject: 

Wombat wrote:
Photo shows right assembly for right side drum - is the left side the mirror image?


it's a fluid return problem....

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