If you have seen any of my recent posts you'll know I recently changed 2 rear callipers and flexi hoses as I had one seize on me. Ever since I did this job I noticed that If I am stationary, and push my brake pedal hard as I can, and hold it down under constant pressure (with engine running, so with servo assist), then the pedal slowly sinks to eventually hit the bump stop. Now you would never drive using the brake like this, so its not a complete show stopper, but worrying all the same. I bled the brakes thoroughly and there is no air in the system as far as I can see, and no leaks whatsoever. I even cycled the ABS whilst pressure bleeding the front callipers (using VCDS). No air detected in system at all - but the pedal still sinks if I old it down hard. So I thought to myself, maybe the master cylinder has a flipped seal, so passing fluid. So today I fitted a brand new Brembo master cylinder and again did a thorough bleed. The issue is still exactly the same - no improvement whatsoever! I know there is supposed to be an ABS bleed procedure on the A6 C6 F4 that you can access using VCDS via group 002 basic options under ABS Brakes, but this option does not work on my car - displays an error invalid group message. Instead I use group 010 to cycle the ABS whilst doing a pressure bleed.
I'm stumped now, and shy of taking it to an Audi specialist, I am out of options unless you guys have any ideas? Thanks in advance, Paul
I'm stumped now, and shy of taking it to an Audi specialist, I am out of options unless you guys have any ideas? Thanks in advance, Paul