Brake Pedal Still Sinks To The Floor

[paul richmond]

[b]Hi there does anybody know much about brakes my brake pedal used to sink to the floor very slowly after pressing it. ive stripped every calliper down and made sure there all greased up when i put them back in so they was good as new also took the master cylinder off to see if that was leaking and it was fine. i bled all the brakes all the way to the abs pump but the brakes are still the same, As anybody got any ideas i was wonderin if it could be the servo were the vacuum is. [/

[Monster-Mat]

you say you have checked tha master cylinder, ...ive had 3 master cylinders go on me...

it could be the servo...but ive not known one to fail yet

[paul richmond]

[b]Hi there does anybody know much about brakes my brake pedal used to sink to the floor very slowly after pressing it. ive stripped every calliper down and made sure there all greased up when i put them back in so they was good as new also took the master cylinder off to see if that was leaking and it was fine. i bled all the brakes all the way to the abs pump but the brakes are still the same, As anybody got any ideas i was wonderin if it could be the servo were the vacuum is. [/

hi there mate i took the master off and expected to see some brake fluid round the end of it because that was my first instinct when the problem occured but it was dry so i made sure it wasnt blocked and put it back on but still got the problem

[Monster-Mat]

the fluid doesnt leak out, it leaks within the cylinder itself, past the seal

The master cylinder piston has 2 sides,

The manual action....You pressing the pedal, to work the braking system

and

The mechanical side....the ABS solenoid causing fluid to push back (when ABS activated)

what happens is that the seal fails and allows fluid to pass between the 2 sides of the piston within the master cylinder

[dave1]

[b]Hi there does anybody know much about brakes my brake pedal used to sink to the floor very slowly after pressing it. ive stripped every calliper down and made sure there all greased up when i put them back in so they was good as new also took the master cylinder off to see if that was leaking and it was fine. i bled all the brakes all the way to the abs pump but the brakes are still the same, As anybody got any ideas i was wonderin if it could be the servo were the vacuum is. [/

hi there mate i took the master off and expected to see some brake fluid round the end of it because that was my first instinct when the problem occured but it was dry so i made sure it wasnt blocked and put it back on but still got the problem

Are you losing any brake fluid?

[paul richmond]

[b]Hi there does anybody know much about brakes my brake pedal used to sink to the floor very slowly after pressing it. ive stripped every calliper down and made sure there all greased up when i put them back in so they was good as new also took the master cylinder off to see if that was leaking and it was fine. i bled all the brakes all the way to the abs pump but the brakes are still the same, As anybody got any ideas i was wonderin if it could be the servo were the vacuum is. [/

hi there mate i took the master off and expected to see some brake fluid round the end of it because that was my first instinct when the problem occured but it was dry so i made sure it wasnt blocked and put it back on but still got the problem

i know wot you mean mate but since takin it off and mesin about with it the pedal sinks further than ever

[paul richmond]

[b]Hi there does anybody know much about brakes my brake pedal used to sink to the floor very slowly after pressing it. ive stripped every calliper down and made sure there all greased up when i put them back in so they was good as new also took the master cylinder off to see if that was leaking and it was fine. i bled all the brakes all the way to the abs pump but the brakes are still the same, As anybody got any ideas i was wonderin if it could be the servo were the vacuum is. [/

hi there mate i took the master off and expected to see some brake fluid round the end of it because that was my first instinct when the problem occured but it was dry so i made sure it wasnt blocked and put it back on but still got the problem

Are you losing any brake fluid?

no not losin a drop mate

[Monster-Mat]

the fluid doesnt leak out, it leaks within the cylinder itself, past the seal

The master cylinder piston has 2 sides,

The manual action....You pressing the pedal, to work the braking system

and

The mechanical side....the ABS solenoid causing fluid to push back (when ABS activated)

what happens is that the seal fails and allows fluid to pass between the 2 sides of the piston within the master cylinder

[ROYT]

For my two pennorth I would bleed them all again into a jar.

Don't re-use the fluid and don't shake the new fluid up.

If it's still not right, back to the master cylinder.

[paul richmond]

[b]Hi there does anybody know much about brakes my brake pedal used to sink to the floor very slowly after pressing it. ive stripped every calliper down and made sure there all greased up when i put them back in so they was good as new also took the master cylinder off to see if that was leaking and it was fine. i bled all the brakes all the way to the abs pump but the brakes are still the same, As anybody got any ideas i was wonderin if it could be the servo were the vacuum is. [/

hi there mate i took the master off and expected to see some brake fluid round the end of it because that was my first instinct when the problem occured but it was dry so i made sure it wasnt blocked and put it back on but still got the problem

aup mate so you reckon more or less try a new master cylinder

[paul richmond]

[b]Hi there does anybody know much about brakes my brake pedal used to sink to the floor very slowly after pressing it. ive stripped every calliper down and made sure there all greased up when i put them back in so they was good as new also took the master cylinder off to see if that was leaking and it was fine. i bled all the brakes all the way to the abs pump but the brakes are still the same, As anybody got any ideas i was wonderin if it could be the servo were the vacuum is. [/

hi there mate i took the master off and expected to see some brake fluid round the end of it because that was my first instinct when the problem occured but it was dry so i made sure it wasnt blocked and put it back on but still got the problem

aup mate so you reckon more or less try a new master cylinder

also is there any particular way to bleed them mate

[ROYT]

I always start with the farthest away from the master cyl.

Not sure if it makes any difference,but worth a try..

[paul richmond]

Thats what i thought mate obviously bleed the abs pump after ive done the four callipers

[Monster-Mat]

Thats what i thought mate obviously bleed the abs pump after ive done the four callipers

and pressure bleed!, gravity bleed will not remove all the air

[paul richmond]

what do you mean bye that mate

[Nitmoi]

Pressure bleeding forces the fluid and air out of the pipes by forcing clean fluid through using a pump rather that the intermittent stabbing on the brake pedal

[paul richmond]

yer but doin that ya just addin more air in the system

[Monster-Mat]

yer but doin that ya just addin more air in the system

erm no your not, read the post before yours......again

[Rob]

yer but doin that ya just addin more air in the system

how do u work that one out?? its a pump that pumps fluid so how does it put more air in the system?