Brake pressure problems

[wishbone]

Brake system
I went to drive the car the other morning and the brake pedal went straight to the floor. Hand brake was ok and after a couple of pumps the pedal and brakes worked normally. I tested up the road and a couple of short trips without problem.

Same thing has happened again now. Brakes are adjusted well. One click locks them then release one click and they run free. Handbrake on 3 or 4 clicks.

Pedal goes to floor but after several pumps you can get a bit of pressure. At that point I tried bleeding the brakes. But when the nipple is released fluid pours from it like it is under pressure. This happens at all 4 corners unless the pressure has been lost and the pedal is back to the floor.

The master cylinder is topped up. It was not low on fluid to start with and there are no air bubbles present when depressed slowly even with pressure.

The front rubber hoses are fairly new as are some of the brake cylinders.

Could something be blocking the fluid returning. I am not sure where because it effects all cylinders so could this be master cylinder or is there a nicer alternative? How do I diagnose from here?

[bmcecosse]

It sounds to me that the brakes are not correctly adjusted--despite your assurance. Rear brakes - slacken off the handbrake adjustment and then tighten the internal adjuster - and then reset the cables. At bthe front - try again with the two adjusters in each drum - 'slightly rubbing' is ok. If none of that helps...check the 'free play' on the pushrod into the master cylinder - it must be there, but should be minimal. All failing - it's going to be a new mastercylinder - or you can try a set of seals....

[wishbone]

Ok thanks. I did follow those instructions for adjustment as you have advised me of that before! I will double check tomorrow.
If the master cylinder fails wouldn't i loose the pedal and pressure? Once I pump up pressure the brakes work and the pedal holds and doesn't creep to the floor. But like I said it does keep pressure in the system because as soon as I release a bleed nipple fluid streams out! That's without my foot on the brake I should add! Can a master cylinder fail with those symptoms?

[bmcecosse]

That is correct - the system is designed to hold ~ 3psi to keep the shoes out close to the drums. It's a sort of 'automatic adjust' system (and always means a single 'long' push if the car has been standing) - but falls away after an hour or two...and certainly over night. So if you are SURE about the adjustment ... I can only guess the master cylinder seals have gone 'soft'...or there are scores/rust on the cylinder wall.