Hi
i have 01 A4Q 2.8l with about 140km. Parked the vehicle for a week and noticed that the brakes were feeling very soft and behaving funny. had to pump the pedal to get an effective braking action where i felt some control; otherwise the pedal would sink with minimal braking effect until it reached almost to the floor and then the ABS would kick-in and i would get the typical chattering but effective ABS braking. there were no warning lights on the dash. the OBD was not throwing any codes. i took it to the shop where they bled the system and replaced the fluid; then replaced master cylindar. in both instances the problem persisted. on the test drive i pulled the fuse for the ABS and the braking returned to normal.

it would appear therefore to be an ABS problem. i tried to remove and inspect the left front speed sensor, but it was seized in place and i ended up breaking the sensor; had to disassemble the axel to hammer the old sensor out. that sensor did not look to be dirty and the hub ring was in good shape. I am understandably reluctant to try to remove an other sensors for fear of damaging a relatively expensive component. I am suspecting the ABS control module but i'm not sure it would solve my problem.
anyone have any experience with a similar problem or any recommendations?
Thanks

.. on the MC.

Sounds bit like a worn or misbehaving pump.

Finally found someone who knew what he was doing! The first thing he did was to check the rear hub rings and sure enough both of them were broken. replaced the rings and the problem went away. i'm a very happy camper