this is a real doozy.......

i have just done a stanza front end conversion......i have machined the discs and re-kitted the calipers

when the car is off and i put my foot on the brakes, the brakes feel very spongy....and pretty much just sponge all the way to the floor....
but after a few pumps they feel great and will stay like that ....UNTIL

when i take off and then go for a drive, the brakes will loose all pressure and it will feel spongy and again will pretty much sponge down to the floor.....

if i pump it while driving it will feel great ...but after driving for about a km the brakes will disappear again...and sponge down to the
floor.....

me and my mate have bled and bled and bled the brakes...and we are 100% sure we cannot get anymore air outa it......

i was also told that maybe i didnt tension my wheel bearings properly and the brakes have to try and squeeze the disc back into place.....anyways we checked that and they are fine.....


does anyone have any damn idea what is goin on....cause 3 brake shops have no clue......

pleeeaaaseeee help

also what is the proportioning valve????

i had similar problems when i first did my swap .... if there are bleeders nipples on your master cylinder try bleeding them, air in the master gives a real nice spongy feel

proportioning valve may be the same as a balancing valve ?? to adjust bias between the front and rear brakes.

good luck

have you bled the whole system including the master cyclinder and rear brakes ? sounds like there maybe be some air in the rear wheel cyclinders. anyone else have any ideas ?

well i havnt touched the rear brakes at all....like they have been left in tact the whole time.....and when i slam my foot on the brakes hard...my rear wheels lock up as the usually do.....but yeh if u reckon they need doin to i will......

as for bleeding the master cylinder......no i havnt bled it........could it still have air in it regardless that i have bled the lines a billion times???

do i not need a proportioning vavle as the discs need different pressure from the back drums?????


let me guys

thanks heaps for ur help

I had the same problem....all air was out etc etc and I found it needed a full rebuild of the booster.
now the brakes work perfectly.
There is a terrific mob called B & R brakes in Blacktown NSW. contact Michael beBoer there and they will fix it and it will stay fixed. They are very good with race cars...and theres nothing worse in a race car then bad brakes.

the brake people reckon my master cylinder is fine cause it holds pressure really well like if i build the pressure up while stationary and hold my foot on the brake...the pressure is great and it doesnt die down.......

I'm not really a brake expert, but lack of expertise shouldnt stop you from having a go ...... Proportioning valve gives you front to rear bias (assuming a front rear split, which 1200's are) Does your master have enough capacity for the new front calipers???? I'm thinking that if it is too small then you will need a couple of quick pumps to get the calipers to go in. Large volume caliper, small volume master= no movement in caliper. then once they are in near the disk, it takes a while for the fluid to bleed back, so you get brakes for a while, but then they go away again.

Booster? Check reaction disc inside booster , on the end of booster piston inside engine bay.

If your back brakes lock up first, then you'll need a proportioning valve on the rear line. I just got one for mine, need to fit it yet.

What car did you get your "splitter/proportioning valve" from, for your setup? Stanza one? or original 1200 stuff?

Does mainly sound like air, or stuffed bore in the master cylinder.

sounds to me like you are getting pad knock off. Its where the disk has been machined wrong and it wobbles. when sitting still the pads adjust and feel fine but when you drive the disks wobble and push the pads back to far. next time you press the brake the pads need two pushes to get them back to where they need to be. You may need to adjust the rear brakes aswell. To check the run out on the disks you should use a dial indicator. Hope this helps. Olboy