Braking problem after brake overhaul & bleeding my system.

[smogthemog]

After a near accident caused by a burst Bridgestone braided brake hose, I decided to give my brakes a complete overhaul.
New Pads, Disks, re-paint callipers and a complete bleed through.

I have a Gunsons brake bleeding kit and I decided I was going to blow out the complete system to each calliper so that air was coming out. I did this on all 4 callipers, re-closed off the bleed nipples and then re-filled the reservoir.
I filled the Gunsons chamber and added air pressure (@ 18PSI) to the system.

I then bled RP, RD, then FP, FD. I did this 3 times around in that order using about 1.5L of DOT4 Synthetic brake fluid.
I also bled the clutch system through too and thats fine.

OK, so now the problem:
Brakes seem to bite alot better now after a week of driving but the Brake pedal still seemed a little spongy than before I started the overhaul - unless you lift your foot whilst braking and immediately re-apply the pedal pressure - then it seems to bite much further up the brake pedal travel and with not so much brake pedal pressure required SO I set too this evening and did a re-bleed of the whole system again using a further 800mL of the same fluid.

I have checked the bomb and that gives 32 pumps before going hard.
No leaks
Clutch is perfect.

It's still the same - Any ideas will be welcomed with open arms

[s2_wot]

did you replace the braided hoses with new braided ones?

[smogthemog]

I replaced both the rear ones with Motaquip ones and added thick heat shrink with glue inside it to the 2 flexi ends.

The 2 front ones are still the Bridgestone ones.

[s2_wot]

Sounds good
While the system was drained down or during refilling / bleeding did the brake pedal go all the way to the floor, you can damage / invert the seal in the master cylinder sometimes by doing that?

EDIT: another question

OK, so now the problem:
Brakes seem to bite alot better now after a week of driving but the Brake pedal still seemed a little spongy than before I started the overhaul - unless you lift your foot whilst braking and immediately re-apply the pedal pressure - then it seems to bite much further up the brake pedal travel and with not so much brake pedal pressure required SO I set too this evening and did a re-bleed of the whole system again using a further 800mL of the same fluid.

When you press the brake initially does it continue to travel towards the floor as if there is air in the circuit or does it go solid only further down than you would like?

If you're driving on a straight road, apply the brakes once then accelerate again and apply the brakes again. Is the travel the same as the 1st time or is the pedal travel less than previously?

[smogthemog]

No, it didn't.

No, it doesn't travel to the floor it just travels further than it used too and feels a 'little' spongy. If I, in effect, double pump the pedal when first braking; say coming into a roundabout, then it feels OK.

It seems to need 2 pumps to make it feel 'right'

I will say though, the pads and disks I took off of it where absolutely knackered! (the Pads where EBC Red Stuff ceramics - Disks looked original)
The pads where all about 4mm and the disks where VERY worn!

I will try the last question tomorrow.

[mcandmar]

Not sure on which the Gunson system is, if its one of the systems that pushes fluid through the reservoir they work great, the cheaper ones that suck from the bleed nipples are useless IMO.

If they need pumped up you have air trapped in the system somewhere, most common is the master cylinder. Early cars have a bleed nipple on the master cylinder, for later cars try pushing the brake pedal in 3/4 of the way in, then let it out really slowly while bleeding. i.e. do it by hand. Repeat a few times and it will get the last of the air out. As above i dont recommend pushing the brake fully in as it will damage the seals on an old master cylinder.

Also make sure the handbrake is off while bleeding the rears, i dont know why but it does make a difference. And if this is an S4 make sure the bias valve on the rear is held fully open, as the rear suspension drops it closes the valve.

[smogthemog]

Its the pressure Gunson system, they are darn brilliant IMHO!
One man job throughout.

Handbrake was off during all the bleeding.

I will re-bleed tomorrow trying the 3/4 pedal down advice.

It's a 1997 (runout model) S6 - AAN 20V - Quattro Avant - C4 chassis

Thanks

[Mikes2]

how much fluid are you pushing through each line.

It sounds like air in the lines. 800 ml for the complete system isn't enough.

18psi is too high. I never go higher than 10, although i don't use the Gunson any more.

[Fat Audi 80]

Why did you "blow out" each brake line? I am not sure it was a good idea to introduce air to the system. I thought the normal procedure was to add new fluid and watch until it runs clear out of each line?

I would try bleeding again and see if any air comes out...

Cheers,

Steve.