I have a GTM Rossa fitted with classic mini running gear. Its a single master cyclinder with split brake circuit, with twin pots at the front and
drums on the rear. When i picked the car up the brakes were bad, i.e. wouldn't lock up. I stripped the front callipers down as one of the pistons
wasn't retracting/moving. I refitted it all (making sure bleed nipple was at top of calliper), checked out the rear cylinders (which look almost
new) and then proceeded to bleed the system with an eazibleed. I did the fronts no problem, but the rear caused problems as no fluid with flow through
with the eazibleed pressurised, so i ended up doing it the old fashioned 2man way. Took the car out, brakes were terrible, you had to pump them to get
it to lock up. So retried bleeding them twice more but no better. I ended up buying a mytivac vacuum bleed kit hoping this would sort it, The vacuum
pump worked well and i could draw fluid through the rears this time. But after a few hours last night, draining litres of fluid through, the brakes
are still rubbish, requiring pumping to get get peddle hard, and even then the peddle can be pushed to the floor.
Can anyone suggest anything?? Master cylinder problems maybe??
You have adjusted the rear brakes I assume? After that it sounds like a dodgy master cylinder.
quote:
Originally posted by adithorp
You have adjusted the rear brakes I assume? After that it sounds like a dodgy master cylinder.
with mini drum brakes also check the wheel bearings - any play in them will ruin your chances of getting a good brake pedal.
sounds like dodgy master cylinder to me. i had a brand new one that was duff from day 1 so don't rule it out just because its new.
I second the suspision about 'just because it's new it should be OK'. Many years ago my brother replaced the Clutch Slave Cylinder on
his GTM Rossa to cure having to bleed the system all the time. It didn't fix it and in desperation stripped down the new Cylinder only to find
that the piston hadn't been ground all the way round so was a poor fit and let air in. A second new Slave Cylinder, checked before fitting, cured
the problem.
Another Rossa specific issue is that the tub didn't allow all that much brake pedal travel, certainly less than in the Mini. So the rear shoes
must be adjusted with minimum clearance.
We also reinforced the mounting brake and clutch pedal mounting fitting to the tub to support it from behind to elimnate any flex.
I guess it's just possible that the old calipers could be letting in air.
Put a flexi hose clamp on each flexi hose,one by one and see if the padal improves.do you get fluid out of the bleed nipple when you do it the old 2
man way?
Chris
Well adjusted rear shoes so that wheel only just about turned, still the same. So I had another look at the mc from underneath, iand it was definitely damp, and looked like rust marks. So decided to remove it and when I pulled the seal back there was loads of corrosion, so can only assume its been seeping for ages. Stripped it down and bore looks fine, so will just get a rebuild kit and retry it. Can defiantly see the thickness of grp reducing available movement of piston, its actually been ground back a couple of mm already to help.