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MG MGB Technical - Clutch hydralics, won't hold pressure

I installed a new clutch master cylinder.... installed as received.... and rebuilt the slave. Now I can't get the bleeder to get all the air out, or build up any pressure. I suspect air is sucking in, and I further suspect the new master cylinder. I'd expect fluid to be leaking out rather than air coming in if the problem was anything but the cylinder. Am I on the right track with the cylinder as the suspect? Should I have oiled the compression rubbers in the cylinder before installing? If so do I have to remove it now to so? Any advice is truely appreciated. Thanks.
Brian

How did you fill the system? I filled mine using an EeziBleed on very low pressure connected to the slave bleed nipple. Filled the system in about a minute and didn't need bleeding. You are looking for slave piston travel of 1/2" to 5/8". Some recommend bench bleeding, which would lubricate the rubbers, before installation but I have never found it necessary (for either brake or clutch) and it sounds a messy fiddle.
Paul Hunt

Brian - Since you probably did not use Paul's method of filling the clutch hydralics, reach under the car and push the rod all the way back into the slave cylinder, then rebleed the normal way. This bushes any air in the slave cylinder back into the line, from which it can be blead out through the bleeder fitting. You may have to repeat the process a couple of times, but it will get the air out of the system. Good luck - Dave
David DuBois

I bled the system by just filling the reservoir and pumping, with a hose connected to the bleeder and waiting for the bubbles to stop.... which didn't happen even after two small bottles of fluid. I will try pushing the slave cylinder back. I also saw a string where someone suggested letting gravity slowly drip the system over time. I'll try that. Other suggestions are appreciated. Thanks!
Brian Denis

Had a hell of a time with mine. Tried it 4 times first. Then professional mechanic friend (Mercedes, BMW, Rover, MG, Mini, etc.) suggested bleeding it backwards. Use clean old style Oil Pumper can and hose hooked to slave after completely emptying the system then pump fluid backwards through the system. 1 time, 5 minutes and done. He doesn't have time to waste with balky bleeding issues so came up with or stole this method.

JTB
J.T. Bamford

I haven't tried it on my MGB, but, similar to J.T.s technique, I've used 100cc plastic syringes for the same purpose with various motorcycles. Easy to verify that there is no air being injected with the fluid.

BTW, it took three people about an hour to bleed the clutch system when a new master cylinder was last installed. One to pump, one to check and keep the reservoir full enough prevent air from being admitted and one to crack the bleeder when necessary.

Good luck,
Edd Weninger

This thread was discussed on 14/07/2003

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