Morris Minor Owners Club

In the technical tips for master cylinder removal

http://www.mmoc.org.uk/index.php?page=320

Rob suggests that this can be done by only removing the small part of the cover plate.
Do I assume that you would have to leave the push-rod assembly in the car to do this as you haave no way of disconnecting the footpedal and spring without taking off the full gearbox cover.

I refurbished the master cylinder in Molly as part of the re-furb and fitted new pipes and wheel cylinders but the brakes only just passed the MOT the day before the rally. So when I got back, I fitted the new shoes and started to bleed the brakes. The fluid comming out was not the clear colour I expected and at some wheels I am getting lots and lots of air, even after using a full bottle of new fluid. So I suspect the master cylinder as there are no signs of any leaks in the system.

I was hoping that Robs method would mean I didn't have to take off the full cover, but I can't see how this will work.

Don't know where he got it from that brake fluid is more flamable than petrol, because it isn't. It's not even classed as a combustible substance! Brakes can get very hot so if it were flamable it would be dangerouse. It's flash point is VERY high dependant on the water content as it is also hydroscopic (spelling sorry!) IE it absorbs water its the water content in the system that causes brake fade as it turns to vapour(steam) when heated.

Once the bolts and pipework are disconnected the MC can be withdrawn through the floor panel. It's fiddly but possible and there is more movement once the MC is diconnected. I think the pedal and the rod going into the MC unscrew from each other.

Check your system for leaks first as any joints that are slightly loose will let air in and I have had ne wheel cylinders fail after fitting so before taking the MC out have a good look around each wheel and follow the pipework and check each joint for leaks.

The push-rod just pulls out of the master cylinder, it's not held in by anything apart from the grip of the rubber dust cover. After all, it's only meant to push in, the return is taken care of by the spring in the master cylinder. So yes, you can leave it connected to the pedal.

I don't understand this business of air getting in at loose joints, surely fluid would get out even more easily so that should be visible and the fluid level would be dropping too.

You can push it against the rod and get plenty of space, squirtage may occur of course, but space isn't a problem.