Timson

Are there any brake guru's out there that can diagnose / verify what's wrong with my brakes.

Just installed brand new 4 pot calipers, new disks and pads front and rear.
Re-connected the braided brake lines and filled up with DOT5.1
Bled all the air out - using the sequence where you work your way in from the furthest caliper from the reservoir.

The problem I am now experiencing is that my pedal travels all the way to the floor (This is after pumping the pedal to take up the slack between the pistons and pads).
I put the pedal to the floor and get a tiny bit of braking force. Pump it to the floor again and the force increases - same if you repeat a 3rd time.
The thing is - if I keep my foot pressed down the braking force does not stay applied - the pressure bleeds away and there's no braking until you pump it again.
Checked the reservoir and unions - There are no leaks - no loss of fluid.

When I get someone to watch the reservoir when I pump the pedal the brake fuid can be seen to swoosh as a jet of fluid comes back into the reservoir.

This appeared to me to be a faulty master cylinder (Why now after all this time)
Went to the dealer......New master cylinder Circa £250 !!!!
Ordered the seal kit to re-con the cylinder - Still £60

Decided to take the master cylinder to bits in lieu of the parts coming on Thursday.

The rubber seals all appear A1 as does the inner body of the cylinder itself - No scoring or crud in there.
There is, however a one way valve type thing which appeard to be allowing air through in both directions. Gave this a blast through with the compressed air line and it seemed to do the trick.
Re-assembled everything.
Bled the entire system again - used another bottle of brake fluid up.

Guess what - same problem exists !!!!

What's going on ?

Don't know if a seal kit is going to cure my problem.
Anyone had any similar experiences / ideas / fixes ??

Tim

Robin MY97Wagon

When you installed the new callipers did you make sure that the bleed nipples are mounted on the top of the calliper thus allowing you to bleed the air out?

awd wrx

it may seem like a stupid question but have you got the calipers on the right way up , with the bleed nipple at the top...

awd wrx

doh , great minds think alike

3barboost

do the calipers maybe have two bleed nipples one inner and one outer both at the top of the caliper

RON

If they are the 'Subaru' 4 pots, then there is only one nipple per caliper, which as stated, MUST be at the top of the caliper, an awful lot of people put these the wrong way round, and all the air just gets stuck in the caliper........
Not sure if the STI Brembo's have 2 nipples per caliper, but even so, they should clearly be at the top either way!!!!

Timson

The calipers have just one bleed nipple on the inside edge which I have oriented correctly as you state - uppermost so that air bubbles will rise to the top.

I've had a Chat with Ian Godney and we seem to be in agreement that the master cylinder is at fault - but exactly what part we can't tell. Don't imagine the one way valve assembly comes with the seal kit anyway.

May try sourcing a low mileage master cylinder from a wreckers rather than stumping up - think of a number and treble it - dealer prices.

On the bright side - At least my new brakes look good.

Tim