brakes constantly need bleeding!

[1-1dicky]

right guys my mates got a problem with his furio converted to S.

his brake pedal is sinking to the flooring e over the space of about a week.
but once they have been bled they are totally fine for another week.
he has replaced the master cylinder, and within the last year has had both rear calipers replaced.

theres never any air that comes out the system neither is there any loss of fluid.

[greyjasper51]

was it an oem master cylinder cus it sounds like the fluid is swapping ends in the master cylinder, it could be brake hoses expanding but i shouldnt think so... could be a porous pipe that under pressure is weeping fluid but wont let air back in...

[1-1dicky]

its not loosing any fluid though, so surely it cant be a leak, and yeah was a genuine master cylinder, :(

[greyjasper51]

it doesnt take much to make the brakes feel bad, think how much the pads move minimal... and how thin the metal brake lines are.. thin, wouldnt take much mate

[scottie_436]

could have contaminated fluid... was it a brand new bottle you used.

Open fluid soaks up water like a sponge!

[1-1dicky]

its sorted now, the rear right caliper was allowing air back into the system