After some advice. Did the brakes on my 2000 A3 1.8T about a couple of years ago, all that went well until I started to bleed the brakes. Halfway through bleeding them (Manual 2 man method) the pedal suddenly sank to the floor. With the car switched off the pedal would feel fine, but when the car was on, the pedal would soften up. Managed to get them so there was some braking albeit near to the floor.

Anyway had the car to a (general) garage, they bled them and even though better than my attempt, it was still not right with braking very low down.

Lastly had the car to an Audi specialist who did the same and had the same results as the previous garage. So even the brakes are adequate (passed through 2 MOT’s ok) its still not right

Fast forward 2 years and I’m determined to get it sorted. Having searched the net on this topic for Audi A3/VW Golf MK IV’s it seems like the master cylinder seals could have been damaged, so I’m looking to get that done.

Any idea’s on how much this would cost (I’m in the UK) and the best tried and tested procedure on carrying this out. I’ve read that the ABS unit would need to be bled using VAG.com.

Thanks in advance

 

I think it may be just air in the master cylinder, so I've got a Gunsons on order

20 PSI, a good seal on the MC reservoir and logs of rags around the master cylinder seems to be the general consensus

Read on one of the posts that the lower nipple (nearest to bulkhead) is bled first then the higher one last.

The system hasn't been run dry so there shouldn't be air in the ABS pump

If doesn't sort it then I'll do the brakes again RL/RR/LF/RF, Clutch then Master Cylinder.

I'll post back with my results

 

I'd like to here the result off that, got the same problem on my 2000 1.8t quattro.
Had the problem long time too. I took it to a garage when I noticed the problem they took the brake system apart and could not find a problem.
Very frustrating.

 

Bled the master cylinder & brakes using the Gunsons (good bit of kit btw)

Made a bit of difference but nowhere back to normal

I think the next step maybe is to get the ABS pump bled but I'll need VAG.com to do that. If that doesn't work then it'll have to be a MC change