Soft S3 brake pedal when engine is running

[danger S3]

Hi Everyone,

ok, so here's what happened.
a couple of weeks ago i went to put new rear pads on my car, while doing that i noticed the rear pistons were pretty siezed. ordered new (refurbed) callipers from eurocarparts.
at the weekend i went to fit the new callipers, the first one i put on i was the offside, i went to bleed it and eventually realised that the bleed nipple wasnt closing. turns out the thread in the calliper was stripped.

in this time of messing around quite alot of fluid dripped out :-( to the point where i dont think there was any left in the pipe or header tank.

I got the calliper replaced and put on the 2 new callipers and bled both back brakes alot using an eazy bleed.
The pedal felt nice and hard with the engine off, started the engine and it was all soft and squishy.

i then bled all 4 corners and got a few air bubbles out the front left.

pedal is still soft with the engine running. it does brake gradually as i press the pedal and if i jump on the pedal the anchors are out and it brakes pretty well. only problem is the pedal feels light.

any suggestions on what could be causing it?

 

[Erikn89nl]

No experience with this myself, but I've seen mention of using VCDS to bleed the ABS module? @<tuffty/> ?

 

[JohnStan725]

Hi sorry I'm not got any information but I have the same issue! Had my front brakes replaced by the garage they are super soft on the pedal they brake loads better when I jump on the pedal or push it on and off quickly. Like to see if anyone can help with this! Mine always squeak really bad and that's not when I'm breaking! Not sure why it's like the disc is rubbing on some metal.

 

[SamHendry]

Not long ago I stripped the banjo threads on one of my rear calipers, the car sat for couple days while I sourced parts, during that period the system emptied itself of all brake fluid. Once I had the parts, put it together then bled all four corners including MC (didn't bother with abs module)and the pedal was soft not sharp like it was before, anyway after 500 miles of driving the pedal came to life and sharpened up, or maybe I just got used to it?

Brakes do feel better than they did before and that's with oem discs along side rear pagid pads and mintex up front.

What formation did you bleed them?

Have you bled the master cylinder?

 

[danger S3]

Cheers for the replies guys,

I had a look at the VCDS ABS bleed thing but wasnt sure how it worked so kinda left it.

I'm not sure i bled them in the correct order but the backs were bled alot, then front left then front right, then the backs a bit more for good measure

i have not bled the master cylinder, i also saw down the back of the engine below the header tank there was a bleed nipple which I'm assuming is on the servo i couldnt really see, so i havent bled that either, wasnt sure if it was needed or not..

 

[SamHendry]

Rear right, rear left, front right, front left.. Pretty sure that's the order you want to bleed them. That's how I did mine. There is two nipples on the MC that should get more air out the system. Be careful when cracking the nipples! Mine snapped

 

[jojo]

You MUST bleed the master cylinder, if the brake fluid has dropped below the reservoir levels. If that doesnt sort your issues, then you need VCDS to cycle your ABS pump whilst you bleed the system.

 

[danger S3]

Thanks very much guys,

I was hoping i wouldnt have to bleed the master cylinder but it makes sense. if i remember correctly it's not the easiest thing in the world to get to because of wee things like subframe and others.

any tips on the best way to bleed the master cylinder?

 

[jojo]

Thanks very much guys,

I was hoping i wouldnt have to bleed the master cylinder but it makes sense. if i remember correctly it's not the easiest thing in the world to get to because of wee things like subframe and others.

any tips on the best way to bleed the master cylinder?

Lol, remove charge pipe, and it's there! Chances are, you won't have a 6 or 7mm ring spanner, so you need to use a socket and stuck a cloth or loads of towel under it to catch the brake fluid. Using your pressure bleeder, just undo it, hear the air release, then tighten up. You don't need to bleed it like a brake calipers, waiting for loads of bubbles.

 

[666markyboy]

welcome to the 8L ...they can be a right pain in the ****... I changed the master cylinder on ours and it's always been a soft pedal ever since and I've tried everything bar taking it to Audi... thing is it always passes it's MOT,,, I think maybe they do just have a softer than average pedal

 

[danger S3]

cheers guys, sorry to ask a silly question but is the master cylinder not behind the brake pedal i.e. underneeth the car?
i could see a bleed nipple below the brake fluid tank but i was thinking that was on the servo for some reason

 

[666markyboy]

the plastic tank you fill with fluid sits directly on top of the master cylinder... there should be 2 bleed nipples, one reasonably easy to see the other a right pain on the s3

 

[danger S3]

Thanks for all the info guys, i think i was getting the master and slave cylinders mixed up.

so after a couple of weeks of driving the car i had started to get used to the lite pedal but the other week i had another go at bleeding things.

i removed the turbo charge pipe, attached the eazy bleed pressure bleeder
bled the two bleed nipples on the master cylinder
bled the back callipers again
and bled the clutch (just for good measure)

i tried the pedal and it felt solid, started the car and it still felt rubbish while sitting still :-(
i was annoyed so started tidying the garage, when i left the garage i drove down the road and went to brake for the first corner and nearly headbutted the windscreen.

seems to be working nicely now guess my muscle memory for braking had changed over the 2 weeks it was soft.

Thanks again guys

Ali