Spongy brake pedal

[666markyboy]

Trying to get the car ready for it's MOT as been sat in the garage since before Xmas.... my brakes have never been particularly good so i've been having a look at them today.... all the rears were seized up so i've freed them all up and tomorrow i'll be having a bash at bleeding them.... i've bled them before but it made no difference but this time i'm goona do the master cylinder too and also cycle the ABS pump with VAGCOM..... at the back of my mind i'm worried that the master cylinder maybe knackered but if i pump the pedal without the engine running it quickly becomes a really solid and hard to press... only when i start the engine does it become soft and spongy.... now to my way of thinking if the cylinder was knackered and being the first item in the system it would also be spongy without the engine running does this make sense ????? next thing is what actually power assists the brakes ?? is it the ABS pump ? or is there some sort of servo and what do i have to do in VAGCOM to get it to cycle the pump.. i really need to get these brakes sorted as it wont pass an MOT the way they are

 

[Dazmo]

The best advice i can give you is to use paragraphs, then i might be able to understand what your talking about....or maybe not.!

 

[666markyboy]

sorry.... wasn't aware it was an English exam..... perhaps if you knew less about English and more about mechanics you may have been able to help me,,,, thanks for the input though i shall take it onboard

Sometime

 

[Jonay]

Although I have an 8P, bleeding the brakes makes a massive difference.

When was the last time that you had your fluid replaced? I dont mean topped up or anything I mean totally replaced? Once you do that and still find a problem, then you can start worrying about your Master Cylinder.

For your question - there is a servo that assists. (But thats all I know, never worked with VAGCOM)

 

[s3dave]

sorry.... wasn't aware it was an English exam..... perhaps if you knew less about English and more about mechanics you may have been able to help me,,,, thanks for the input though i shall take it onboard

Sometime

Pmsl......
The brakes are servo assisted and is on the left hand firewall, alot of people have problems with bleeding brakes on these?
are you using a pressure bleeder?

 

[Dane]

My brakes are the same despite changing to LCR brembos and having the system professionally pressure bled and fluid replaced with dot 4.1 IIRC /what ever tuffty uses. The Pedal is as you describe it with the engine off and with the engine on.

New pads are next on the list.

 

[666markyboy]

right well i've bit the bullet and bought a new master cylinder for peace of mind if nothing else, i'm fortunate my quatty has no ESP so it's a cheaper cylinder but still set me back £70 also got a gallon of fluid and my preassure bleeder.... Looks like it's gonna be a real pain to change though as there's not much access.. i'll keeps ya posted and let you know how it goes

 

[Alex C]

The best advice i can give you is to use paragraphs, then i might be able to understand what your talking about....or maybe not.!

What? I read all that fine, he's used punctuation and has a good grip of the english language, dont know what your on about. Better than abig block of text in txt spk and no punctuation.

Markyboy I grade you B+, good work!

Yes, your brakes are servo assisted using one of the vac lines that come of your inlet manifold i think, which is why the brakes feel spongy when starting the car

 

[666markyboy]

Why did you guys not warn me what a pig of a job it is to change the master cylinder ??? what a Bar Steward of a job... tip for anybody else doing it .... dont bother trying to undo those pipes on the bottom of the unit.... unbolt it from the servo and just pull the sucker up bending the pipes as you go it dosn't give you much more access but certainly helps, just got to bleed it all now .... tomorrows job

 

[DJ_Troopa]

I've got this same problem with mine!

Going to get the brake servo hose checked out today as we think it's got a split, apparently ANOTHER common problem in our cars, i'm starting to think the Audi S3 is a common problem itself!

 

[karls s3]

Why did you guys not warn me what a pig of a job it is to change the master cylinder ??? what a Bar Steward of a job... tip for anybody else doing it .... dont bother trying to undo those pipes on the bottom of the unit.... unbolt it from the servo and just pull the sucker up bending the pipes as you go it dosn't give you much more access but certainly helps, just got to bleed it all now .... tomorrows job

mate did this cure the spongey pedal problem..

 

[666markyboy]

In a word ...... NO i have decided since doing this that the origional master cylinder was actually fine,,,, the car was laid up at the time and i was un able to take it for runs for legal reasons and i bled the brakes several times using lots of different methods,,,,, since then the car is now back on the road and drivable but the brakes are still pants .... however , even though i stripped them down and added extra springs to the handbrake return i now think the problem is bedding in of the rear pads and the rear self adjusters not working correctly.... if i pull the handbrake on a couple of notches i get a very firm pedal...... it's a bit of work in progress i wanna get some new rear pads and disc's next payday and strip them down yet again as i'm now thinking it's more mechanical play thats causing the soft pedal rather than air in the system

 

[s3dave]

Makes sense, do the rear calipers wind themselves back up to take out the slack? (or supposed too)

 

[karls s3]

In a word ...... NO i have decided since doing this that the origional master cylinder was actually fine,,,, the car was laid up at the time and i was un able to take it for runs for legal reasons and i bled the brakes several times using lots of different methods,,,,, since then the car is now back on the road and drivable but the brakes are still pants .... however , even though i stripped them down and added extra springs to the handbrake return i now think the problem is bedding in of the rear pads and the rear self adjusters not working correctly.... if i pull the handbrake on a couple of notches i get a very firm pedal...... it's a bit of work in progress i wanna get some new rear pads and disc's next payday and strip them down yet again as i'm now thinking it's more mechanical play thats causing the soft pedal rather than air in the system

sounds just like my ibiza cupra problem i had even to the point of pulling hand brake and it making it better..

 

[kent_phil]

Makes sense, do the rear calipers wind themselves back up to take out the slack? (or supposed too)

Did this have a solved and happyending? I've got very similar symptoms on my '99 S3 having ****** my brakes on a track day - have had the pads, discs, front calipers and master cylinder replaced plus many (many many) pressure bleeds and it's still not biting.

Thanks in advance,

Phil

 

[audi-tk]

When cars running does it makes a wired spongy noise when u press the pedal down

 

[kent_phil]

Can't say I remember this but out of interest what would this indicate as at fault?