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MG MGB Technical - Bleeding Clutch : (

I wish I could say what a lovely little bleeder it is but I can't! It ain't happenin'.

I have tried to bleed the clutch the traditional way by opening the bleed nipple and pumping the clutch pedal, plus an eazi bleed pipe. Hardly anything came out at all.

My second attempt was to attach a piece of pipe to the slave cylinder bleed nipple and pump the slave cylinder. This easily pushed lots of air out of the master cylinder and drew in liquid. There was lots of gurgling going on in the clutch master cylinder reservior.

Driving off, the clutch was fine. I stopped up the road to speak to a neighbour and when restarting the engine, the clutch refused to engage. No better than before.

Any suggestions as to my next move greatfully received. (The car in question is an MGBGT 1978.)

P ONeill

In the Thread "cable clutch" some one suggests connecting the brake caliper bleed nipple to the clutch slave, and using the brake master cylinder to back pressure the system. I was wondering if you could do this using an Ezi bleed on the brake master cylinder.
c cummins

What's worked for me is to unbolt the slave and compress the piston with a C clamp. Keeping the bleeder in the highest position possible, re-bleed the system. This should remove the air that gets trapped inside the slave when it is still mounted to the trans. RAY
rjm RAY

I agree with Ray. The only way to bleed the slave is to keep the piston compressed during the process.
Steven 67GT

As above.

I usually tie the arm/pushrod back with a piece of stout wire.
Dave O'Neill 2

My method involves placing a flexible bleed tube onto the open slave bleeder nipple and the other end into the clutch master cylinder reservoir. Pump the master cylinder slowly and repeatedly until all air bubbles disappear. This recirculation of the brake fluid eliminates all air in the system.
Frank Grimaldi

Thanks very much one and all .... I am just about to try again so wish me luck!
P ONeill

I think the MGB slave cylinder is the same as a non verto mini slave cylinder - a tip for bleeding a mini slave cylinder is to push the slave rod in an out while and have an assistant gentle pump the clutch pedal - this seems to " prime" the slave cylinder
might be worth a try ?
M Benoy

Doing the same thing, having the same problems. I don't want to reverse bleed using the brakes, as the blake fluid is old but the clutch fluid is new. (I know, why not fluch the brakes first...). Anyway, archives and other internet chatter is inconclusive as to how much movement I'm looking for at the slave cylinder. Some say 1/4", some say 1/2". I've got 5/8" but no battery and hence I cannot check with the engine running (I know, get a battery...). Please help!


The trouble is with pushing the piston back into the cylinder it can find it easier to suck air in past the seal than brake fluid all the way down from the master, as the internal spring pushes the piston back out again. On clutch bleeds on several cars I have only ever used the reverse method, first with an EeziBleed on the slave bleed nipple which means you can use fresh fluid, and after that by linking it to the left-hand brake caliper which is much easier. Paradoxically this means that air and fluid is leaving the cylinder by the *lower* of the two ports (the bleed nipple should always be in the upper port) but has caused no problems for me. If you pump in the normal direction unless the rear of the car is raised significantly above the front for some reason, the exit point from the cylinder is always at the highest point, you don't need to remove the slave from the bell-housing - unless you have a faulty or incorrect slave of course. 1/2" to 5/8" travel is the norm, if you have the latter then it should be fine as that is the greater of the two. You say 'the clutch refused to engage', do you mean the *gears* refused to engage? And it ground when trying the select reverse? That - clutch dragging - can happen for other reasons than insufficient slave piston travel.
PaulH Solihull

Should be: "I've got 3/8" ...

That may or may not be enough, it does seem to depend on individual components. That can be caused by wear in the mechanical linkage at the pedal end i.e. ovalled holes in the pedal and master push-rod, and grooved clevis pin. I'd expect that to give a low biting point though. Can you feel the weight of the clutch as you push the pedal down? Or is there very little back-pressure?
PaulH Solihull

This thread was discussed between 08/05/2011 and 16/05/2011

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