Good Morning, all
I have an Audi a4 (2009) with a front right sticking brake.
I have had the car at a garage, and they were not able to find the fault (i've also checked/ changed a few parts myself). I took it to Audi in the end and their mechanic diagnosed water in the servo/ master cylinder and quoted for replacement. They claim debris under the scuttle panel was blocking the drain holes. I've taken the scuttle panel off and cleaned it as best as I can - there was some debris but nothing major.
However, my understanding was that the brake lines split and go to each wheel from the ABS pump, not the master cylinder and I'm therefore not convinced by their diagnosis. Maybe somebody on here has had a similar issue or knows where to look?
At highway speeds when the car is up to temperature, the front right brake lightly sticks. This causes a vibration through the pedals and steering wheel. This brake is also noticeably hotter than the other side.
The issue is intermittent and sometimes starts as soon as I get on the motorway (without using the brakes), other times it doesn’t start until the car is up to temperature and the brakes are warm (again it can start without using the brakes - it gradually creeps in), finally, it can happen when the car is warm, driving at motorway speeds and I use the brakes. After a short duration of time, it feels like the brake works itself free and the vibration stops but it can come back again later (with or without braking).
The following parts have been changed:
- Calliper
- Brake pads and discs (I have since changed the pads again as they are wearing unevenly). Inner right pad looked like a cheese wedge shape.
- Flex hose
- Wheel bearing
- Abs pump (with a second-hand unit)
- Brake fluid
- The calliper carrier bracket
Audi said they had the car on the rolling road (or whatever they use to test the brakes) an they noticed the brake fluctuating. The brakes squeak and when I'm braking lightly as low speeds I can hear the squeak 'pulsing' (for lack of a better word) like i'm dabbing the brakes (only the front right does this).
If anybody has any suggestions, this would be greatly appreciated.