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Rear brakes lock-up. - Printable Version

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Rear brakes lock-up. - EcLiPsE - 03-24-2013 09:31 PM

Ive tried a disk brake conversion and December the new caliper seal popped on a trip.
Ive used engine oil to top-up because ive had no spare brakefluid.

Only drained and flushed system about three weeks later with Dot4

Bus has been standing in the mean time to fit a better disk brake setup at the back.

All done now and she brakes like a sportscar but....
Brake pedal becomes "stiffer" the more I drive it, a trip to town and back +\- 15km had the pedal so sensitive.... later there was no play when putting hour foot n the pedal... it brakes immediately when touched.
Later I could feel that the brakes aren't releasing at all and the bus pulls heavier.

I bled the system quickly and pedal is back to +\- normal with about 20mm play before it starts to get stiff & brake normal.

Went to church today and parked, got out and stood there chatting for about 5min behind the bus......all of a sudden the brake lights comes on..... Yea, brakes locked?
Released the bleeding-nipple and brakefluid squirted out as if someone was pressing down on the brake pedal...

It has something todo with either heat(building up while driving) or the movement of the seals in the cylinders when brakes are applied?

Any input would be appreciated.
It suspect damaged seals in the master cylinder?

The calipers fitted at the back has slightly warn sliding pins but still looks reasonable. All seals in calipers was replaced with new...(Could there be a problem with these seals?)

Re: Rear brakes lock-up. - syncromad - 03-25-2013 09:23 AM

the oil may have damaged the brake pipes, making them swell internally, they will let brake fluid in under pressure but will stop it going bake to the master cyl, travel may also be wrong for the master cyl, stopping the fluid from returning,

Re: Rear brakes lock-up. - EcLiPsE - 03-25-2013 03:50 PM

Could you please give me an idea of the procedure "step-by-step" on the removal of the master cylinder?
Going to replace all seals

Re: Rear brakes lock-up. - Nico - 03-26-2013 02:06 PM

I can scan the procedure from the workshop manual and email it, if you like.

Re: Rear brakes lock-up. - deanace - 03-26-2013 02:43 PM

take out the speedo cluster
loosen all the steel pipes from the master cylinder
remove the 2x nuts securing the cylinder to the booster
remove the master cylinder

as easy as that

Re: Rear brakes lock-up. - EcLiPsE - 03-26-2013 08:19 PM

Thanks guys
Im a impulsive person, all removed, seals replaced and back in again!

Thanks for the replies, why did I hear guys dont like doing this job? Thought it was suppose to be a very hard job....

I've actually enjoyed this one!

Will test tomorrow and let you guys know.

Cost me 1lt CleanGreen(to clean/flush pipes from possible leftover HX3 ;-))
2lt Dot4 Brakefluid
New master cylinder seal kit @ R150.00

About 15min to remove Master Cylinder and 15 to re-fit.

Flushing the pipes and brake calipers took quite a while....

Re: Rear brakes lock-up. - syncromad - 03-27-2013 07:24 AM

Clutch master is a cow, brake master is fine,

Re: Rear brakes lock-up. - EcLiPsE - 03-27-2013 06:32 PM

lol, you put it funny Stuart...
Im worried about that one but for now it seems to be working fine....

Took it for a 50km town-trip today, brakes excellent!

Handbrake cables will be done tomorrow