# Spongy brakes after RS4 8 pot brake kit install?



## talx (Apr 4, 2003)

Well I installed an RS4 8pot brake kit after bleeding the brakes everything was ok and actually still had a good feel to the pedal and it wasn’t spongy at all
A week later after installing Audi TT front spindles and control arms although I didn’t disconnect the brakes the pedal became spongy but only after driving without braking for a bit if I pump the brake while driving the pedal will become hard once more and then again after driving a bit when I brake it will become spongy once again I tried bleeding the brakes once more but it did not solve the problem anyone have any ideas ?


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## GTijoejoe (Oct 6, 2001)

*Re: Spongy brakes after RS4 8 pot brake kit install? (talx)*

Before installing the spindle/knuckles of you couldn't drive the car correct?
Than installing the correct spindle/knuckles you could bolt up the system?
.... and then you drove and got the spongy pedal... but only after driving, and than pumping you can get the pedal to become hard again?...
This sounds like piston roll back to me, the spongy feeling is the fluid consumption by the roll back, there is some dead pedal until you move all 8 of those things to meet the resistance of the pads/disk. 
This is only an assumption because I don't fully understand your process/condition.
What size MC are you using?


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## talx (Apr 4, 2003)

*Re: Spongy brakes after RS4 8 pot brake kit install? (GTijoejoe)*


_Quote, originally posted by *GTijoejoe* »_.... and then you drove and got the spongy pedal... but only after driving, and than pumping you can get the pedal to become hard again?...


correct
I installed the kit but then realized I didn't have full steering potential because caliper mounts where hitting the control arms so I swapped in the TT spindles and control arms after the swap the problem began I didn't have this problem before installing the TT parts I know this because I drove the car for 3 days until I found and installed the TT parts 
I also thought that maybe it’s the master cylinder but how is that possible unless it broke as soon as I stopped the car in my garage just before I started work on installing the TT parts
I did not disconnect the brakes when I installed the TT spindles and control arms I only unbolted the caliper from the spindle and zip tied it to the spring with the brake line still connected so I wouldn't need to bleed the brakes once more
after I bolted everything back together I took the car for a test drive and noticed the problem
once more I most add the pedal was absolutely fine before I installed the TT parts and there was no problem with the pedal feel (was not spongy at all)so the master cylinder (original 23.8)was coping well with the 8 piston calipers 
im thinking maybe an air bobble got released when i hanged the calipers off the springs but i bleedid the brakes once more and there where no air bobbles in the oil
and wouldn't air in the system make the pedal spongy all the time not making it possible for me to pomp the pedal getting it hard again?
_Modified by talx at 12:48 AM 9-8-2009_


_Modified by talx at 12:50 AM 9-8-2009_


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## GTijoejoe (Oct 6, 2001)

*Re: Spongy brakes after RS4 8 pot brake kit install? (talx)*

It sounds like you have air in your lines, I can't explain how.... or you can install your old spindles again and see if your pedal comes back








Of course I laugh but there is a very very very slim chance that its deforming the spindle ears ~0.001%
Do you have SS lines? I would also doubt your MC is acting funny, unless its got a lot of miles and perhaps a coincidence.
Also bleed the RR brakes too. The more pots the more places for air to hide, you can also tap on the calipers with a rubber mallet.
See where that gets ya....
PS those 8 pot brembos are NAZZZTY!


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## talx (Apr 4, 2003)

*Re: Spongy brakes after RS4 8 pot brake kit install? (GTijoejoe)*

well I did rebleed the brakes once more nothing working brakes are still spongy I have ss braded lines
I’m thinking it must be the master cylinder ore….someone has also suggested I might have a damaged caliper
you guys think if the caliper isn’t holding pressure I will be able to see oil residue?
If the caliper is damaged I will havto return it ore get a repair kit to replace the pressure seals


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## GTijoejoe (Oct 6, 2001)

*Re: Spongy brakes after RS4 8 pot brake kit install? (talx)*


_Quote, originally posted by *talx* »_well I did rebleed the brakes once more nothing working brakes are still spongy I have ss braded lines
I’m thinking it must be the master cylinder ore….someone has also suggested I might have a damaged caliper
you guys think if the caliper isn’t holding pressure I will be able to see oil residue?
If the caliper is damaged I will havto return it ore get a repair kit to replace the pressure seals


If you had a damaged caliper that was leaking pressure, you would surely see brake fluid. If you pump the pedal, ~50 times you should be able to see your fluid level decreasing......if there is a system leak. 
It also can be a master cylinder seal issue, solved by replacement.
If the caliper seals are faulty, and if returning the caliper and getting another is FREE, than of course that is the best option.


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## talx (Apr 4, 2003)

*Re: Spongy brakes after RS4 8 pot brake kit install? (GTijoejoe)*

Ok today I disassembled the calipers to check for oil leeks and nothing they are completely dry I also tried bleeding the brakes once more this time I used a hammer to see if any air was trapped in the caliper 
Well there was a bit but maybe 2 or 3 bubbles in each caliper I also did the rears as well and nothing there are only a bit better
After talking to David from Zeckhausen who has bin a great help he told me if the master cylinder was damaged it would sink all the way down when pressing on it when the engine is off and that doesn’t happen so I’m out of ideas 
I guess I’m going to havto replace the master cylinder to see if it’s the fault for sure 
Also I’m trying to source one of the T4 transporter 25.4mm master cylinders with ESP if I’m at the point of changing the master cylinder might as well upgrade it


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## A2Carat (Jan 13, 2003)

*Re: Spongy brakes after RS4 8 pot brake kit install? (talx)*

Well, if you think about it, when you drive, the pedal gets soft until you pump them up again. There is an internal leak somewhere if there isn't an external leak. If the pistons in the calipers move in and out freely, then I put my money on an internal leak - and that's at the master. Give it a shot.


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## GTijoejoe (Oct 6, 2001)

*Re: Spongy brakes after RS4 8 pot brake kit install? (A2Carat)*

It may be as simple as you still have hidden air in the system....


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## AP Racing - Chris_B (Jan 30, 2009)

*Re: Spongy brakes after RS4 8 pot brake kit install? (A2Carat)*

It's pretty amazing you had a decent pedal when you first installed them. You just increased the front piston area by 24.1%, which is a MAJOR change. It's hard to believe the master cylinder is up to that increase in volume, not to mention the huge bias shift to the front axle you now have to contend with.


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## davojuri (Aug 28, 2009)

*spacers*

Hi

did you use any spacers to install this kit.
I have 8x19 ET35 wheels, is there any need for them?

Regards
Davor?


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