I've been kicking myself and wishing to do permanent damage to a 64 850 recently in its long journey to being re-registered.
Brakes have been changed by a previous owner from the single to the twin leading shoe brakes of the Deluxe/ Mini K.
The original master cylinder was rekitted. Brakes were bled, but the pedal went to the floor. No leaks visible.
Looked at the wheel cylinders, all have now been replaced, master replaced, all soft and some hardlines such as those on the front have been replaced. Brake master clevis pin replaced.
New master cylinder has been bled from the top with a valve.
Still after bleeding, brake pedal goes to floor.
Sequence of bleeding is back, passenger first, back driver second, front passenger first and front driver last.
Pedal will pump up, but not hold pressure.
Brakes adjusted up. Still no change, pedal to the floor.
Remove front drums, back front adjusters off, clamp shoes to furthest position back.
Bleed as before, pedal will pump up, but it goes to the floor. No leaks.
The only part not replaced or removed and inspected is the brake proportion valve. But no leaks there.
I never had this trouble with my own car 30 years ago when I did not have to clamp the front brakes to bleed them.
What am I doing wrong.
I've even started talking to the car and telling it it is going to Simsmetal on a truck.
It is sending me mental.

I'm pretty sure the book told me to do the front left first, then front right, back left then back right.

It could be possible you've got a big air bubble in between the master cylinder and the back brakes due to fixing the master cylinder but still have fluid from the back valve to the brakes.

I just had to keep on bleeding - did it maybe 8 times filling the one man bleeder till I got it through.

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You could perhaps also try one of those vacuum bleeders that suck the fluid from the reservoir back if you have a compressor. They are about $100 at places like repco but if it solves your problem, it may be worth it.

If the pedal does keep going to the floor however, then it may still be indicative that there is something wrong. If there was air and fluid, you would expect some form of pedal to be forming I would have thought.

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It can be quite difficult to get a newly reconditioned master cylinder to start pumping after they are re-fitted. I can recommend the Gunson Eezibleed, they are about $50 from the UK. Their instructions have a section explicitly for early Minis which recommends bleeding the master cylinder on its own, before attaching the brake lines to it. It helps to have an old flexible brake line you can fit temporarily to the master cylinder to guid the overflowing fluid into a jar.

Tim

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1951 Morris Commercial J Type Van
1955 BSA C11G
1961 Morris Mini Traveller
1969 Triumph TR6R
1977 Leyland Moke Californian

Exactly what Tim said. . .unhook the outlet line from the master and bleed that first. . .it can be difficult to get them 'started' after a rebuild.

Is it possible that the master cylinder is the one for the clutch, or whoever rebuilt it forgot to fit the little non-return valve at the top of the spring?

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Curly
'64 Cooper 'S' (Group Nb spec)
'67 Mini Marcos GT www.mm7056.wordpress.com

Was the master cylinder bench-bled before fitting to the car? The pedal doesn't use the full length of the cylinder, so air can stay at the top if it is only bled after attaching.

I would also have a look at the bias valve. I also had issues with the pedal dropping to the floor (though mine was a dual-circuit clubby). It turned out to be the bias valve, a bit of cleaning and $3 worth of o-rings fixed the problem.

Have you tried clamping the rubber hoses and checking the pedal? That will let you know if it's master cylinder/ bias value side or wheel cylinder/ adjustment side.

I'll throw another into the mix (sorry).

The rear cylinders sometimes get air trapped in that you just can't get out because of the angle they are on (practically horizontal). Solution ..... jack up and support the rear of the mini and bleed the rear brakes then do the fronts. Work from the furthest away from the master cylinder to the closest (which is what you did). Also, 'un-adjust' -if there's such a word - all brake shoes first. Once all the air is out, adjust them up again and there you go.....brakes.

OR.....as the other guys say, bleed the master cylinder first.

Good luck with it.

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Rod
http://smg.photobucket.com/albums/v607/Rodney/

Thank you for all your comments.
I will check the master to see if it does have the return valve.
I don't have a gunson easibleed but I will do a bench bleed.
As for the proportion valve, I think I better pull it off and check it for any build up as the rear cylinders do not bleed well.
There is some air in the system and I need to get it out.
The method of bleeding that I used in the late 70's is not working and I certainly did not have this trouble.

I'm having trouble bleeding my brakes as well...
Has what looks too be a new tandem master cylinder, all new lines, willwood brake adjustment valve and metro 4 pots on the front. I have an Air Boy (one that attaches to the air compressor and sucks through) and the rears have bled up fine. But when doing the front I keep getting air in there. Have tightened all the new lines and its not leaking out any where. Could it be the master cylinder but only on the fronts?
Sorry for the addition to the thread

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