Brake Problem

[Jon]

During my Bronze’s refurbishment, I changed the front brakes to the Metro four pot caliper / vented disc set up from my dead Mk3. From everything I’ve read on various Mini forums it seems the conversion does not require a change of master cylinder. My system, while passing the MoT without any trouble, has excessive brake pedal travel before much retardation occurs. Because I had to move house before the car was finished, my local Mini specialist made up the brake pipes to suit the later stepped bore master cylinder that I’d fitted, and bled the system, several times and by various methods. They are at a loss as to why there is still so much pedal travel, despite the brakes working fine, and without the pedal needing to be pumped.
They conclude that either there isn’t enough fluid displacement from the master cylinder, or there is some other spurious fault in the system that they can’t find.
Any suggestions?

[Hans Efde]

If you have a brake servo, it's probably in the brake servo. I had a similar problem and geoff as well. I got rid of the brake servo and made an adaptor plate with an adjustable rod. So no play between the pedal and the master cylinder anymore. Geoff changed his brake servo and problem solved. Also Eddie had a long lasting problem that his brakes didn't bite that well either. I suggested he removed the master cylinder from the brake servo (with the pipes on, it's possible) and put something on the rod end that is sticking out the brake servo. He placed a cap, the first one was too thick so his brake were activated. The second attempt was better and now the master cylinder is activating the brakes as soon as the pedal travel begins.
Another earlier discussed problem is that the pedal needs to be modified for extra travel. This is well documented on the Yahoo form. Hope this helps.
Hans

[Stuart]

Have you still got that brake fail valve on the bulkhead? If you have throw it in the bin and run without one.

[Jon]

Stuart,

The brakes are a lot better now after a couple of hundred miles. I got the pipe I needed to eliminate the remote servo from the system, but haven't tried it yet.
Initially I thought the 'improvement' might just be me getting used to them, but there is definitely a lot less pedal travel now. I will try it without the servo, and if that improves things I may just ditch it entirely. It's a Mk 1 Cooper servo which you don't seem to be able to get service kits for any more, but should be a straight swap for a Mk3 one.

Jon

[Stuart]

I have more or less the same set-up minus the servo and bulkhead fail valve and find the brakes really powerfull, the pads are nothing special either. Having a full-length brake pedal helps a lot compared to those that were shortened on factory built ones.

My also showed the same longish pedal until everything was bedded in a bit.

[grahamc]

Geoff, Sorry for late reply and have not read all the link, We had bleed problems on a Mini fitted with Metro 4 pot calipers wouldnt bleed properly without a pressurised blleed kit and when we cured the front the rears that were partialy siezed/sticky caused a problem if you can imagine a sticky cylinder moving but not all the way due to you releaseing the pressure by bleeding the brakes, The system bleeds due to the piston sticking but when you can apply full pressure it moves again, Only found out by trying to rotate the rear drums as we were bleeding they grabbed initialy but a bar showed that you could rotate them if you tried as the pressure backed of, the wheel cylinders were moving but not returning

Regards Graham