A3 brake issues..

[confusionhunter]

OK its not an S3 but the systems are essentially the same.... tried posting on other forums but no luck....

Bleedin Brakes....
Its a curse not a request on how to bleed brakes!!

My brakes are knackered and I dont know whats wrong..... but there is a bit of a story.... The issue is on a an 98 A3 SE Tdi 110, I have a 2000 Bora SE 1.6 16v too and as far as I can tell the brakes are identical....

Anyway, I suffered catastrophic brake failure on the passenger rear caliper, so I changed that and the flexi hose..... but ever since then the brakes have been spongy and with the engine running the pedal slowly sinks to the floor...... I fitted new front discs too and thought just incase I managed to get air in the M/C I though I might bleed the brakes through. I have VAG com so I bled the ABS pump, all four corners and the 2 on the Master Cylinder......but I did this manually using the age old pumping technique.....

No difference pedal feels great until you turn the engine on and it slowly sinks to the floor.....

So I read up on the usual brake issues on uk-mkivs.net and thought Id managed to flip the seals on the MC.... SO...I bought a new MC and an Eezibleed kit...... fitted it and bled the system all 4 corners and the 2 nipples on the MC as well as the clutch cylinder too..... No difference.....

Ive checked for leaks in the servo system, cant see any and even if there were I dont see how that would cause these syptoms. The only thing I havent done is bleed the ABS pump again....

.... so I'm a bit stuck really.....Help....!

I can apply HARD pressure on the pedal with the engine off and it will stay solid for as long as I can apply the pressure, but with the engine running it slowly sinks to the floor every time even if you pump it up..... ive checked the 4 corners for fluid leaks too...and dont appear to be losing fluid from the reservoir.....

It went through an MOT on Sat and failed on this sinking pedal(I knew it would)....so there I bled the ABDS pump again 8 times as ELSAwin instructs you to(seeing Ive changed the MC)

No difference....
I suppose I could check for leaks properly by jacking the car up and getting underneath......... I tell you, if I find a leak i'll be Very pee'd off with the MOT place wasting my money on an MC.......as they should have spotted any leaks. and pedal sinks so many times there would be fluid everywhere!

Also reading on ross tech: http://www.ross-tech.com/vag-com/cars/absbleeding.html

that when bleeding the ABS pump all 4 wheels need to be off the ground.... Why?

as far as I can tell there are no load sensors or anything so I dont understand why that is.... I did it anyway last time but Im confused as to why..... my wheels are big enough I dont have to take the wheels off to bleed the brakes, so getting it the the air seems an uneccessary pain in the bum.... unless anyone here knows different?

Any one have any ideas on this? The problem doesnt happen when the servo doesnt have a vacumm either.....

any thoughts would be appreciated.....

Any one have any ideas???

Cheers.
Mark.