Desperate - Brake Pedal Travel

[HHWATBB]

Hello, new on here, wonder if anyone help my poor Mini Cooper get through it's MOT without bankrupting me first!
It failed having a couple of minor things, but also a 'brake pedal spongy'. I changed the back discs and pads as they were ready anyway. The front pads were also worn, so they (and the front discs) were also replaced. The pedal still had excessive travel on it, so the guy then bled them all. No difference, he told me it needed to go to a BMW dealer to have the ABS pump bled. I took it to a non-BMW ABS brake specialist, who bled this system, but called me up to say it made no difference and that he thought the master cylinder needed changing. So I told them to do that, guess what? Yeh, no difference. He took it for a road test and said they worked OK and didn't feel much different to other Mini's he'd drove.
The brakes work fine, if I do an emergency stop etc. But if you keep applying pressure to the pedal it keeps going down to the stop. If the engine is not running the pedal is high and rock solid. Any ideas anyone? Thanks in advance.
Ta Pat

[mab01uk]

Common problem but no simple answer so far.............
See here:
http://www.mini2.com/forum/wheels-ty...al-travel.html

[HHWATBB]

Thanks for that, interesting thread, mine too is a 2003 model. I'm going to take it to the tester and argue to toss with him. It does seem to get worse the longer the journey. If the cars cold, the pedal seems better at the start of the journey, strange.....

[Frank.B]

I have an 02 Cooper with the same problem. Engine off, hard brake pedal, engine on, pedal will slowly go to the floor if you keep pressure on it. I am using High Temp (Motul) brake fluid plus after market racing pads and rotors. Took it on the race track yesterday, tricky to heel and toe with a low brake pedal but braking is still good. Bled the brakes between runs with no sign of improvement. Have also replaced master cylinder with genuine part, wasted $700 getting that fitted. The only thing left is the brake booster? Any thoughts or experiences with that?

[Frank.B]

Following on from my last comment I disconnected the brake booster and went for a drive. DO NOT TRY THIS AT HOME KIDS. I HAD LOTS OF SPACE AND NO TRAFFIC. The result was a very hard pedal but no matter what I tried I could not make the pedal soft or depress it more than 10%. The braking effort was good but I nearly pulled the steering wheel off! My conclusion is that the booster is overloaded when you hold the pedal down for more than 5 seconds and some sort of relief valve action kicks in. The other odd thing is if you rev the engine to 2500 then push the brake pedal it doesn't go soft as quickly.

[dsakko]

Here in Aus a BMW official mentioned to me an unofficial figure of 10% of the 02-04 Coopers and Cooper S's had faulty master cylinders.

Mine blew up 3.

Solution is to get it resleeved and new seals. Can't remember how much it was but any brake place should be able to do it. Unbelievably good after.

A review of the master cylinder prior to overhauling showed excessive tollerance between the piston and the bore in my master cylinder.

[Frank.B]

Quote: Originally Posted by dsakko (original)

Here in Aus a BMW official mentioned to me an unofficial figure of 10% of the 02-04 Coopers and Cooper S's had faulty master cylinders.

Mine blew up 3.

Solution is to get it resleeved and new seals. Can't remember how much it was but any brake place should be able to do it. Unbelievably good after.

A review of the master cylinder prior to overhauling showed excessive tollerance between the piston and the bore in my master cylinder.

I replaced the master cylinder without fixing the problem. I still have the old one. Have not been able to track down a seal kit. Who supplied yours? Would like to try a reworked master cylinder on my 02 Cooper.

[dsakko]

Mine was a generic kit which wasn't designed for the MINI. I dropped off the master cylinder and picked it up the next day so I have no idea what they used, but I do know it was a matched seal / sleeve kit and required machining of the master cylinder.

[Frank.B]

Quote: Originally Posted by dsakko (original)

Mine was a generic kit which wasn't designed for the MINI. I dropped off the master cylinder and picked it up the next day so I have no idea what they used, but I do know it was a matched seal / sleeve kit and required machining of the master cylinder.

OK. I will try that with my local Brake guy. Thanks for the tip.

[Frank.B]

Quote: Originally Posted by Frank.B (original)

OK. I will try that with my local Brake guy. Thanks for the tip.

Still in trouble. I now have my master cylinder back re-sleeved back to standard but told no kits are available for this size. !!!!!!!!!!!!!!!
Any chance you would pass on the contact details for your local guy. I will send the thing over to him to fix.

[dsakko]

Sure will do. Will PM you shortly.