Another rear brake issue

[wantafaster1]

Right, Mk2 mini has failed mot on rear footbrake imbalance. Shoes and drum used but like new, wheel cylinder and flexi new, but can turn wheel by hand. Tried then cracking open the pipe from limiter to wheel, not much fluid coming out.

So, when I then cracked open the pipe going into the valve, there's loads of pressure and fluid. Now, when you pump the pedal I definately feel the valve "working" or clicking with my hand on it. The pedal feels good and firm. Also, opening a rear bleeder won't let the pedal go to the floor, but it goes to the floor when you open the pipe going into the valve.

Any thoughts?

[mk1coopers]

You have to back the pedal pressure off slightly when you are bleeding the rear cylinders, then you should get a click from the compensator and the pedal will go to the floor, as to the imbalance, adjustment?, different sized cylinders?, partially seized cylinders on one side?

[wantafaster1]

The other cylinder was new last year, then the one on the offending wheel replaced today. Didn't measure the bore myself but possible I suppose. Didn't have this bother last time!

Many thanks. Any other theories?

[bpirie1000]

Can you inspect the pipe? Are there any marks in it.. Could also be the rubber flexi hose that has an issue....

[wantafaster1]

Flexi and cylinder new. Getting good pressure going into limiter but not out.

[WNX700H]

Not sure which type of rear valve you have but assuming it is the one on the rear subframe then it is designated a shut off valve so at a given line pressure determined by the spring in the valve the piston inside shuttles and closes the valve , then no matter how much you increase the line pressure via the pedal there is no pressure increase to the rears .

So when you bleed the rears you need to make sure you dont generate enough pressure to close the rear valve.

[Lord Croker]

I agree with mk1coopers, you do often have to back off the pressure on the pedal to bleed the rear brakes, I have often had to open bleed valves by at least one & a half turns to allow the valve to release, if the fluid doesn't have completely free flow, the valve will lock off. If the valve was at fault, it would affect both rear brakes. As the bad brake is the one with the new cylinder, it is worth checking the bore diameter against the opposite one. Did you do all the work yourself? I hate to say this, but could the brake shoes have been fitted wrong way round?

[guru_1071]

id say its either the cylinder size, the shoes or a damaged flexi hose.

the valve is doing what it is supposed to

[IAIN]

Tried then cracking open the pipe from limiter to wheel, not much fluid coming out.

So, when I then cracked open the pipe going into the valve, there's loads of pressure and fluid. opening a rear bleeder won't let the pedal go to the floor, but it goes to the floor when you open the pipe going into the valve.

Any thoughts?

If the fault is only on the new side I would look there first. So the fluid is at the equiliser but not at the cylinder. So check that it is getting to the cylinder by loosening off the pipe at the cylinder and try again. If fluid is getting to the pipe end but not out the cylinder take the bleed nipple out and re check for fluid. The nipple or pipe (copper ?) may be fauly or blocked.

[wantafaster1]

Symptoms exactly the same before and after the new parts fitted. Car done 80 miles since last years mot so nothing wore out in the meantime. Bled with an ezibleed. The old cylinder wasn't sticky hence new flexi hose as well. I can physically turn the wheel when the brake is pressed.

There was a new cylinder put on the other "good" side last year cos it was stuck, and we had no trouble at the time. Shoes, drum and backplate as new, very frustrating.

Its the offside rear, as you look at the assembly the leading edge, or "gap" in the lining is bottom left, and top right on the other one. Like I say, it passed last time......

[IAIN]

So are you getting fluid through the cylinder now?
Another 'silly' thing I thought of was one of the brake adjuster tappets could fall out and be missed when fitting the shoes this would only give adjustment on one shoe and not lock up .

[wantafaster1]

Well it passed MOT! Now breaking evenly both wheels. Wasn't paying attention but suspect the shoes were on wrong beforehand, after a few miles bedding in everything ok