Banging my head against a wall with this one.

 

The Fabia VRS had the 312mm front disc upgrade, before this the car was left with no front calipers fitted for about a week, so air has been able to get into the system. After fitting it was bleed with a sealey pressure system. the pedal still felt spongey so ive bled the system twice more since then still with no success.

 

with the engine at tick over i pump the brake pedal and it becomes more resistant, much like it is when the engine is off. the moment i rev the engine, the pressure drops and the pedal goes back to feeling spongey/soft.

 

ive read on the MKiV forum that some people need to bleed the master cylinder, but i cant see any form of bleed nipple from the top side of the engine bay. Ive also used VCDS to bleed the ABS pump too.

 

What have i missed?

 

 

Have you checked the 'servo pipe' isnt split/damaged?

I had a look but didnt remove the pipe. and i didnt see any spilts, 

 

that said with a can of brake cleaner, when spraying around the vacuum lines or near the tandem pump the engine revs would shoot up for a second, but i didnt think that there was a direct link between the vacuum lines and the intake due to the fact its turbo charged, unlike NA engines.

any other ideas anyone?

any other ideas anyone?

I had this with my Fabia except on drums! It was perfect for the first five hits and then it went really spongy in the end it got most of the braking replaced by a mates garage!

Have you let the brakes bed in a little bit?

Using the power bleeder is the best way but have you tried the old fashioned way of up and down on the pedal when someone opens and closes the bleed nipple? Just push the brake pedal a little bit at a time though.

You can do quite a few checks yourself just depends how good you are with the tools and what equipment you have.

Have you let the brakes bed in a little bit?

Using the power bleeder is the best way but have you tried the old fashioned way of up and down on the pedal when someone opens and closes the bleed nipple? Just push the brake pedal a little bit at a time though.

You can do quite a few checks yourself just depends how good you are with the tools and what equipment you have.

He is rather good with them judging by the work he does with them and his knowledge

well the first and third times i used the power bleeder, the 2nd time we did it the old fashioned method.

 

in total ive done about 300 miles on the discs n pads (brembo 312's and Ferodo 2500's)

 

 

as said with the engine running i sprayed the vacuum lines from the tandem pump along to the brake servo, there was a change in revs when spraying near the tandem pump but i did have the intake hose to the Air box off, so it may have pulled some of the brake cleaner through the air filter.

He is rather good with them judging by the work he does with them and his knowledge

 

haha thanks jack!

 

just this one is confusing me, as i cant seem to find any vacuum leaks and i dont know much about the brake system on the Fabia, i jsut know my fiesta was alot simpler for its braking system! lol

haha thanks jack!

just this one is confusing me, as i cant seem to find any vacuum leaks and i dont know much about the brake system on the Fabia, i jsut know my fiesta was alot simpler for its braking system! lol

Was that one or the few things that worked on it?

Try finding a bit of rubber hose to run to the intake see if it makes a difference

The pedal would be hard if you had a servo problem, but the servo pipe splitting is a common issue (the hard plastic one) so might be worth looking into with the airbox and intake pipe fitted.

300 mile should be enough to let them bed in, enough to give a good enough feel on the pedal anyway.

It's hard to say over a forum but a few things you can do might help work out the issue.

- To see if it's master cylinder you could remove the connections and fit blanks, with all blanks fitted and nipped up start the engine and feel the brake pedal, it should be rock solid.

- if you have the crimping tool to squeeze brake flexi hoses (or mole grips if your careful) I suggest squeezing the passenger side front and then seeing if the pedal feelings different, if not take it off and try the drivers. This would help narrow down the issue to one wheel or a master cylinder.

ok cool, whats the easiest way to remove the vacuum line into the brake servo? it is quite far down in there and IIRC even on the petrol models its bit of a pain to remove as it clips into the servo

It's got tapered ridges and just pushes in about an inch, easy enough to remove and refit but might be tight In the rubber seal if it's never been removed.

If you have the engine running for a little before removing it, you should hear it hissing as you start to remove it, it's just letting the pressure out but is a good sign if it's holding pressure and not leaking out.

i thought that if the vacuum line to the brake servo was split, it would create a hard pedal?

 

This is a soft pedal which after a few pumps (with the engine running) stiffens up.

The pressure is used to assist your braking. A spongey pedal to me means air in the system. Like I said earlier I don't think you have a problem with your servo or pipe.

hmm ok.

 

Just where ive bled it 3 times, i thought any air would have been forced out by now. and i didnt think Air in the system would explain why i can build up the resistance of the brake pedal when i pump it.. surely that means the vacuum isnt returning the servo to its correct position? 

hmm ok.

Just where ive bled it 3 times, i thought any air would have been forced out by now. and i didnt think Air in the system would explain why i can build up the resistance of the brake pedal when i pump it.. surely that means the vacuum isnt returning the servo to its correct position?

Fluid loss?

With the engine off, pump the pedal then hold pressure for a few seconds.

Keeping pressure on the brake, start the engine.

What happens?

With the engine off, pump the pedal then hold pressure for a few seconds.

Keeping pressure on the brake, start the engine.

What happens?

And if the servo is working it should go down about 1/3 of am inch to 2/3rds iirc

right now the car has been standing for a few hours

 

pump the pedal, pedal gets stiffer, start the car and the pedal very slowly goes to the floor.

 

i cant see any fluid loss

And if the servo is working it should go down about 1/3 of am inch to 2/3rds iirc

 

what do you mean?

 

brakes arent my strong point, trying to get my head around it as i go along... :/

what do you mean?

brakes arent my strong point, trying to get my head around it as i go along... :/

Right mate hop in the car ignition etc off and put foot on the brakes then start it up keeping foot on the brakes and the pedal should drop slightly which would show servo is good

right now the car has been standing for a few hours

pump the pedal, pedal gets stiffer, start the car and the pedal very slowly goes to the floor.

i cant see any fluid loss

A bit of dodgy dave methodry but would it help pumping it with lid off a few times?

A bit of dodgy dave methodry but would it help pumping it with lid off a few times?

 

already tried that

There's bleed nipples on the master cyclinder (2 iirc) and theres also a bleed nipple on top of the gearbox

I also believe if you have a lot of air in it you need to bleed the abs and this can only be done via vcds programming (thats off the top of my head)