Strange brake problem

[Extra 300 Driver]

Hi all,

I thought it time to clean up the bulkhead around where the master cylinders sit. One I did all that I bled the system and had a good clutch but nothing on the brake. So I bled it again, pressure bleed a before, and still nothing. Took tha master apart, didt see any obvious problems but honed it and put a repair kit on to be safe. I have a GMC227, yellow tag.

No I have it all together, and bled, I have a strange feel to the pedal. Have of the movement does nothing, then you can feel the primary piston contacting the secondary piston and the brakes feel normal. They work well, but I have a long pedal.

Any ideas? If I cant sort it soon I am going to rebuild the master again and take a second look at the locking pin of the secondary piston.

Thanks all and have a safe Christmas.

[cooperman]

As it's the braking system, don't take any chances. Go and buy a new master cylinder to be on the safe side. Having had little success in the past with honing, and bearing in mind the paramount importance of being able to stop effectively, don't, please, take any chances with your life over the cost of a new cylinder.
The only things I ever rebuild on a Mini braking system are the caliper seals and pistons. In fact I did a pair of them on Friday - bloody dust seals! Got there in the end though.

[bandad]

Did you fix this problem?
What was the problem?
We have EXACTLY te same issue with an 83 mini - we are desperate.
The pedal travels half way and then the back brakes lock nicely. Nothing at the front.
Please help!

[Cooperman]

It's the tandem vertical master cylinder. They are a real pain in the proverbial and always have been. The cylinder gets a 'step' worn in it which causes seal failure. Then, if you hone it and fit a repair kit it never seems to work OK. The only solution, and once again bear in mind that it's the braking system we're talking about, is to buy a brand new master cylinder.
Again, for the benefit of anyone who doesnt know, the pressure relief valve (mounted on the bulkhead cross member) on cars of this age has METRIC connections for the brake pipes, whilst the other ends of those pipes are IMPERIAL. Yes, really, you couldn't imagine a less safe design. Well, it was Austin-Rover, so maybe it's to be expected.

[bandad]

Thanks for the warnings.
We have already encountered the odd ended plumbing.
We also discovered that AP disc calipers should ALWAYS have the bleed nipple at the top!
Everything working now.

[guru_1071]

bandad said:

Thanks for the warnings.
We have already encountered the odd ended plumbing.
We also discovered that AP disc calipers should ALWAYS have the bleed nipple at the top!
Everything working now.

bob

i get about 2 people a month at work who have fitted the front calipers upside down.

it causes a lot of head scratching!!!!!, its now one of the first questions i ask when people have issues!