9 replies to this topic

[Rusty Rocket]

Well after 2 and a half years rebuilding my Mini, got it through the MOT today, clean sheet, no advisories, well chuffed.

 

Been for a drive about afterwards, done about 20 miles. Got home to find o/s/ rear brake smoking like a bonfire. Let it cool down, and eventually managed to get the drum off.

 

I cannot see anything wrong inside at all, the only thing that seems out of place is the cylinder retaining clip on the outside of the back plate, it is not seated correctly, allowing movement of the cylinder, could this cause them to jam on, or are there any other suggestions.

 

Standard drums on rear.

8.4" discs on front.

Early type front / rear split master cylinder(recent new seals fitted)

Has the proportioning valve bolted to bulkhead in engine bay.

 

Any help would be greatly appreciated.

 

Gone from a great high getting the MOT, to a real low now it's not working.

 

[Gremlin]

Shoes adjusted properly? Handbrake adjusted properly? Handbrake off when driving? :))

[Rusty Rocket]

Hi Gremlin,

 

Shoes were adjusted correctly, handbrake set up and working great, passed MOT with flying colours.

 

Handbrake was not on whilst driving, did check that one.......

 

Had to fully unwind the adjuster to get the drum off, going to check the handbrake linkage in the drum just in case, as it has only been used in anger at the test, so something might have moved.

 

Just having a brew, then going back to it.

[Gremlin]

May have siezed slightly, make sure it's all nice and free and grease it up

[Rusty Rocket]

well, I have stripped down the shoes, and refitted, put the cylinder retaining clip back on, properly this time, and adjusted it all up. 

 

After about 7 miles the brakes start to bind again, the brake pedal also becomes harder. Climbed underneath and undid the bleed screw and released some fluid, hey presto, brakes not stuck anymore. Drive off again and the situation repeats.

 

So, what could I be looking at.

 

Master cylinder(GMC 173, fitted with new seal kit from Somerfords), front / rear split system.

Pressure reducing valve( FAM7821)

Or the rear wheel cylinders.

 

All the hard pipes and flexible pipes are new, so in theory should be ok.

 

Any suggestions greatly recieved

[Jordie]

rear wheel cylinders would be cheapest and easiest thing to rule out.

[Rusty Rocket]

Cheers Jordie,

 

Was sort of thinking that way, as they are about the only thing mechanical on the car that I have not changed / refurbed.

 

Will get a pair tomorrow and see how it goes, otherwise I think it will be a new m/cylinder and different reducing valve( as per Keith Calvers articles)

[Gr4h4m]

Rear flexi pipe not letting fluid back? How old are they

[dklawson]

Rear flexi pipe not letting fluid back? How old are they

 

That was my thought also....  However, in post #5 above Rusty says the flex pipes have been replaced.

 

Changing wheel cylinders may be cheap but I doubt that will address this problem.  You said that releasing the bleed nipple released pressure.  A stuck wheel cylinder won't trap pressure.  Since you said this is limited to one side it is also not likely to be the master cylinder.  It sounds like blockage after the brake lines split left and right at the rear of the car.  It may be a twist in a flex line or similar.

[Rusty Rocket]

Thanks guy's for all the suggestions,

 

After rechecking the operation, it turns out that both rears were locking on

 

Stripped and checked every thing on the whole system, wasn't completely happy with the rebuilt master cylinder, so fitted a brand new one.

 

This the led to another problem, the later type(GMC227) has less braking force for the rear, so was unable to get a brake at all on the rear.

 

Removed the pressure regulator from the front bulkhead, and piped direct from m/cylinder to front + rear lines, great stuff, now able to bleed rears, and get a great pedal feel.  Brakes are now superb, nice light feel for gentle braking, and stops real well if you stand on the pedal in a hurry.

 

So after about 50 miles of testing on straights and cornering at various speeds I am happy, so it's of to the classic car show at Raby castle( Durham area)