Soft Brake Pedal - Urgent

[bigm]

Hey guys,
brakes are very soft,they have been bled. the car still pulls up when the pedal is on the floor..
i am running r31 rear end, so does this require a larger master cylinder?
urgents thanks guys

[charged]

it may pay bleeding the M/C, how much bigger are the rear pistons now ? if the master is too small it will create a spongy long pedal

[bigm]

how do i bleed the master cylinder?

im not sure on the piston size increase. its the caliper from a VS commodore rear..

[ke70dave]

how do i bleed the master cylinder?

im not sure on the piston size increase. its the caliper from a VS commodore rear..

your best bet is to measure it. take off the caliper (dont take off the hydraulic line) and get your calipers out.

then do the same to the original drum brakes, rememeber there are 2 pistons in a drum brake slave cylinder.

then compare the 2 and it will tell you if the calipers significantly bigger than standard and thus causing your pedal to fall away.

i would have thought that since the standard MC is a 2 piston/chamber item, the pedal should still be nice and firm if the fronts are bleed properly?

failing that....more bleeding! (ps ive never blead a MC before and its always worked fine...)

[sundee]

was your rear end drums before u changed to disc? have u removed the little duck bill piece from the bias valve? in the rear section of the valve. if not it needs to come out

did u bleed the system longest line to shortest?

[Hen may possibly be a nut]

I always seem to need to bleed the brakes at least twice before I get a good pedal. Maybe I'm just a nuffy, but it may pay to try again.

Also check to see if anything in the rear is leaking (I assume you just fitted it). And conceivably you could have torn the seals in your master if you pushed the brake pedal to the floor while bleeding it.

Hen

[Jonny Rochester]

Generally, when people say "brakes are very soft,they have been bled", it means they have to bleed the brakes.

The pedal feel is mostly to do with the front brakes vs MC size. The rear brakes normaly would not have as big an effect on pedal feel as the rear brakes are typically smaller. Rear brake size and type will effect bias of course.

If you have pedal creep, you need new seals in the master.

[Golberg]

My old master cylinder shat itself when I bled it for the first time after putting the brake system back together. When driving the car the brakes would still work, except they'd only pull up just before the pedal hit the floor.

Internal seals were shot and the master was leaking out the back. Have a look at your booster and see if there is any brake fluid on it and if there is you've found your problem.

[bigm]

that looks to be the issue thanks golberg. exact same symptoms
well ill get a new one for the new car, no point in in putting it in the fucked car. lol
thanks guys,