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MG MGB Technical - Bleeding the Clutch

I've got a new slave cylinder and a new flexible hose. I've got a new clutch, all 3 pieces. I've bled the clutch both downwards and upwards using an Eazi-Bleed gadget, but I cannot get more than just over 1/4 inch movement on the pushrod. The clutch works OK with no sign of dragging, but the "bite" point is quite close to the floor.

Is it likely to be a problem with the master cylinder, and if so, is it worth re-rubbering it or do they just fail again quickly afterwards.

Mike
Mike Howlett

Did you bleed it downwards first then upwards? If so open the bleed screw and pump out all the fluid with the pedal, then refill it from the slave using the gunsons. With only 1/4" of travel you must still have some air in there, unless the clutch pedal, pin and push-rod are very badly worn. Bad MC seal results in either no pressure or pressure but if you hold the pedal on the floor in gear the clutch gradually engages.
Paul Hunt

Thanks for that Paul. It doesn't seem to be master cylinder, and yes I did bleed it down then up, so I'll try emptying it out and starting again from the bottom. Incidentally, do you have the slave in situ or dangling off the pipe when you do this bottom-up procedure? And if you are dangling (so to speak), how do you prevent the piston from blowing out.

Ye gods, there could be all sorts of innuendo in that sentence!!

Mike
Mike Howlett

Mike - One fix for your problem would be, now that you have blead the system normally, push the rod and , by extension, the piston back into the slave cylinder as far as it will go. This will push any remaining air back into the line from the master to slave cylinder. Once that is done, re bleed the system. This will expell all the remaining air. I have used this method for years, even on my Mazada truck and it works every time. Good luck - Dave
David DuBois

I know folks appreciate a little feedback, so I want to say thanks to both Paul & David. Last night I pumped out all the fluid as Paul suggested, and then unbolted the slave and let it dangle on its pipe. I used a long bolt and a gently applied G-clamp to keep the piston pushed right in like David suggested. In this position the bleed valve is the lowest point of the entire circuit.

I then re-filled with the Gunsons Eezibleed from the bottom up using a tyre with the pressure reduced to below 10 psi. Worked first time. Thanks again to you both.

Mike
Mike Howlett

Glad to see you have sorted it. To be honest I can't really remember if I had the slave attached or dangling, but I do know I didn't clamp the piston in place. I used very low pressure from a spare tyre - just a few psi, which may not have been enough to move the piston if it *was* dangling.
Paul Hunt

This thread was discussed between 23/01/2003 and 24/01/2003

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