In this post, a fault is considered that causes noise, vibration and judderfrom the front axle of the Audi A6 on operating the brake pedal.
The affected models are:
Audi A6 from 2002
PR: 1LB, 1LT, 1LF, 1LG, 1LA, 1LX
Note: The PRs make reference to the vehicles equipment level and are shown on the first page of the maintenance service manual.
|Detail of the PR in the vehicle's service manual|
The front brake judders, brake noise is heard which is transmitted to the steering wheel, and even vibrations on smooth brakingin the front axle.
PROCEDURE AND SOLUTION
Brake judder can be attributed to several causes, which depend on environmental conditions, on the temperature reached during brakingas well asthe driver's driving style.
Carry out the following checks:
- Check the thickness variation of the disk around its entire diameter using a dial gauge.
- Check the lining deposition on the disk after thermal loading (carry out a test journey with vigorous operation of the braking system).
- Check possible corrosion of the brake discs.
- Blueing of the disk indicates high thermal loading of the braking system.
- It is very important to check the wheels are balanced, this may considerably increase the amount of judder during the braking phase of the vehicle.
- Above all, check possible clearances in the front wheel bearings.
Once all the points described above have been checked, and no play has been detected in the front wheel bearings, fit a complete front brake kit, made up of subframe A stops (mounted on the front bushes) and a kit made up of front brake discs and pads.
Repair reference kit:
Front bush stops (A): 4B0 399 291
Front brake kit 8D0 615 301 M / 4B3 615 301
|Subframe stops and brake disc|
After replacement of the parts, the brakes must be run-in in the following way:
Drive the vehicle at a moderate speed, for example, in town in the normal way, then decelerate the vehicle from approximately 100 km/h with a light pressure on the pedal to approximately 40 km/h.
Repeat the process and allow the system to cool for approximately 5 minutes.
Forceful braking must be avoided throughout the whole brake running-in process.