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MG MGB Technical - rebuilding clutch slave cylinder

I'm rebuilding my clutch slave cylinder and I am having trouble getting the seals in. My question is , should I put some oil on the seals to help them slide in OR use some brake fluid to lubricate them?
WRD William

Brake fluid only!
Art Pearse

Are you sure you mean the clutch slave? That should be easy to get the seal (singular) in, it just sits between the plastic disc on the spring and the flat back of the piston on the ones I have seen. The masters and brake slaves are a different kettle of fish.
PaulH Solihull

Thanks for the info. Found that if you slop up all the componants with brake fluid, things slide together. master cylinder was a little more difficult . Moss did not send directions with the rebuild kit and I had a plastic spring retainer that just did not fit. Still not getting full travel with the slave cylinder pushrod, any thoughts?
WRD William

Air in the hydraulics, worn pedal to master linkage, or bits missing from the master! What do you regard as full travel anyway, 1/2" to 5/8" seems to be the norm.
PaulH Solihull

By the way, I have also rebuilt the master clutch cylinder.I'm only getting about 1/4" (5mm) travel of the Slave pushrod. Not enough to engage the clutch. I have bled the line from master cyl to slave and tried from the slave to the master by pumping fluid through the bleeder valve. but with no improvement in push rod travel. I have even taken both cylinders apart and started from scratch twice. Any other hints or thoughts would be appreciated.
WRD William

WRD,
check out the flex hose from the body to slave. If it's gone "soft" it could be expanding under pressure limiting the amount of fluid available to move the slave.
Replace with a uprated one.

MGmike
M McAndrew

The clutch hydraulic system can be difficult to bleed completely. If any air remains in the system, it will compress when you operate the clutch pedal. This reduces the travel of the slave pushrod. To help remove the air, open the bleed valve and push the slave pushrod all the way into the slave cylinder before you start the bleeding procedure. -G.
Glenn G

It is very important when bleeding to close the nipple when the pedal is down and open it again when you lift the pedal repeating this process until all bubbles have died away. If you don't do this air tends to be drawn in past the bleed nipple threads when the pedal is lifted.
Iain MacKintosh

If you push the slave piston all the way into the cylinder only let it out again *very* slowly to allow fluid to be pulled all the way down from the master or it can suck air in past the seal when the internal spring pushes the piston out again. Seals are only designed to seal in one direction.
PaulH Solihull

I too, have had problems bleeding the clutch hydraulics. My solution is to put a length of clear plastic tubing onto the bleed nipple on the slave and the other end into the bottom of the master's reservoir. Fill with brake fluid, open the bleed valve and have a helper pump slowly and repeatedly until the fluid in the tube is free of bubbles (10 or so pumps). Tighten up the bleed valve, top up the fluid in the reservoir, put the cap on and you are ready to go.

Frank Grimaldi
Frank Grimaldi

How is that different to the usual method of having a much shorter length of tubing going in to a jam-jar on the ground containing some fluid?
PaulH Solihull

I would think it would not be as good as the jam jar. I've always heard that you should not reuse the fluid in the jar since it is aerated. I always discard that fluid.
(properly)You would be pumping it into the master cyl.

Ralph
Ralph

This thread was discussed between 22/06/2011 and 14/07/2011

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