all four brakes sticking on after a complete overhaul
Turbo Mini Forums

I'm having a very weird issue with the brakes on my car. I'm running:

Stepped bore dual line AP master cylinder
8.4"caliper set ups on the front
standard bulkhead mounted pressure limiting valve
standard drums on the rear
goodridge hoses

All of the components including the master cylinder and pressure limitng valve are brand new apart from the r/h caliper which was rebuilt a couple of thousand miles before the car was taken of the road.

The brakes have been bled using a gunson one man brake bleeding kit and no air is n the system.
The brake pedal is right at the top with little or no travel at all and the brakes are currently stuck on.

I tried to diagnose the problem by getting someone to press the pedal while slackening the unions on the master cylinder. When a litte fluid was lost the unions were then tightened and the pedal was released. This method totally free'd the brakes off and the pedal now had a nice amount of travel before feeling very firm indeed which was brilliant.

The problem was that after a few depressions the pedal was once again right at the top with no possible travel and all four brakes were stuck on.

My diagnosis is a fauly master cylinder? Could it be possible the seals are not leaking and not pulling the fluid back through when the pedal is released and instead allowing fluid past them from the reservoir, therefore acting like a one way valve?

Any help would be greatly appreciated on this as i'm all out of answers on this one.

Edited by adcyork on 12th Aug, 2010.

the only fault is with whoever has installed the pedal/master.

The actuating rod isnt returning sufficiently to allow the fluid back into the reservoir via the fill holes in the master.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

As Steve says 100%.

Would this by any chance be due to me using the same pedal as i was using when i was running the standard '86 on servo?
I welded a sleeve in the larger hole in the pedal to reduce it down to the size needed for the new master cyl.

Almost certainly. Get the right pedal fit it job done.