Master clutch cylinder won't fill up

TBH I don't really understand your problem, because I only vaguely understand your explaination.of it. Pressure in the reservoir? There shouldn't be any. The master cylinder piston should always return, whether there's fluid in the reservoir or not. Maybe you could explain your findings a little more clearly. Mike.

It should bleed by gravity, right? So, if I disconnect the feed hose, there should be (and is) fluid visible in the hose but then, it should slowly feed the master cylinder, continue to slave and come out through the bleed nipple. However, it doesn't. The hose is full all the time. Even if I apply "artifficial" pressure to that hose (trying to induce flow) nothing happenes. When pumping the pedal, the fluid simply goes 1/2" up and down, instead of feeding the cylinder.

Dreamer

Keep the reservoir topped up, open the bleed nipple a half turn, press down the pedal (some air and some fluid should come from the nipple), WITHOUT releasing the pedal, do up the nipple (this is easiest with two people) Repeat till there are NO bubbles coming out with the fluid. Pedal will now operate correctly.

Exactly the procedure I've tried! But no more fluid comes out because no fluid goes into master. Please, reread my second (or the first) post. At first, I thought that the feed line was somehow clogged but you can see the fluid "moving" (as described) while pumping the pedal.

Dreamer

you should leave the cap off the master cylinder to avoid a vacuum condition. If the fluid will not pump out of the bleed nipple at all, and merely gets pushed back into the reservoir then that would sound like a seal fault in the master. Personally I would put a vacuum pump on the bleed nipple and suck some fluid through if I had this problem, this could be improvised using engine vacuum, preferably with a catch vessel in line.

Mrcheerful

The cap was off all the time. I've also tried the vacuum thing and drawn out some fluid but that's all. Fluid can't get into the master cylinder from the reservoir. Will take out the master cylinder today/tommorow and see what's going on. As I remember, the master cylinder can't be disassembled to renew any seals, right? I'll probably have to buy a new one.

Thanks for the ideas, will keep you posted.

Dreamer

That and the fact that the m/c piston stays down when depressed certainly seems to indicate that the m/c is faulty. I can't see anything but a partially siezed piston acting in that way. Maybe the piston when it does return, is not returning enough to open the port from the reservoir, or the seals have broken up and are blocking the port. Either case could give the symptons you describe. Mike.

A lot of clutch pedals (mainly ford) go over centre when fully depressed, and rely on the force of the clutch diaphragm spring to get the pedal back over centre, so the master cylinder spring can return it fully up. And that combined with the lack of check valves in the master cylinder, makes bleeding clutches a pain.

But it does sound as though the master cylinder has died.

I've put new m/c in and everything fine now. However, standard bleeding procedure left some air in (probably because of m/c being higher then s/c) so I had to "reverse" bleed it - pump fluid from brakes to the s/c. This way, air bubbles came out to reservoir.

Dreamer