Did you bench bleed the master first or put a bleed nipple in the metal pipe hole to bleed the master on the car first

Filled and primed the master cylinder, then bled the slave.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

When the slave seal gets old they suck air in there on the pedal upstroke.
New slave cylinders do this even when near new, just park it for a few weeks... the cure is fit a new seal (buy local), and ensure it has an original plastic seal spreader in behind it.
Seals supplied in the new slave cylinders are rubbish now, IMO. Not fit for purpose...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Yep fit a new brake master cylinder and it lasted about 100ks before the pedal went right to the floor and no brakes. Luckily it was coming into a driveway slowly when it gave way. When we pulled it apart it looked like the rubber grease had hardened and turned into little rubber balls that stopped it doing its job. Cleaned it out and works a treat again.

I have fit 3 others with no problem and have 4 more brand new ones here about to be fit. Clutch doesnt worry me too much but you dont want the brakes not working when you need them!

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1965 Riley Elf
1974 Ex Army Moke
1997 Rover Cooper
2002 JCW Cooper
2003 JCW Cooper S

I have my doubts about unknown greases as well. I cleaned the unit out with metho and reassembled.

LoveB is telling me its sorted itself out now, and is working fine. We were under the pump a little last night with time, but the blasted thing wouldn't give up the last of its air.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

lol yes, nissy the mini seems to have cured herself. There is still a little pedal play. (less than what I had before we replaced it) bite is not quite half of travel or above but its a little lower which I prefer anyway.

doesn't crunch and I dont need to pump it either. So for now I will just monitor it. I may open a new thread to ask about the voltage reg I put in.

When bleeding the clutch slave it always worth pushing the piston in as far as possible and clamping it there while you bleed. Otherwise you may find a bubble of air remains behind the slave piston at the inner end of the slave. Fluid you pump through the system just rolls around behind the bubble and out the bleed valve.

Not really what you talked about but worth a thought.

Cheers, Ian