BRAKE FLUID
Brake fluid is hygroscopic, i.e. it has the ability to absorb water and moisture from the air.
If water has been absorbed, the boiling point will drop, i.e., during high braking temperatures the brake fluid may develop steam bubbles and cause the brakes to fail.
Scheme 1
Over time, brake fluid will darken in color. Dark-colored brake fluid does not indicate anything about its quality. The color forms due to chemical reactions.
| CAUTION | The rubber components of the brake system (boots, seals) do not tolerate mineral oil, gasoline, and cleaning agents! |
Even the smallest amount on a seal or boot can cause the part to change and thereby affect the function of the brake system. The results of an unclean brake system first show themselves months later, causing increased repair costs, especially on vehicles with ABS.
Scheme 2
A = Boot original size
B = Boot swollen through contact with mineral oil
It is implied by the previously mentioned points that
Keep containers of brake fluid closed securely. This is to make sure that no oil, dirt or cleaning materials and no air moisture can enter the container.
Store containers of brake fluid away from oil (even hydraulic oil) and cleaning fluids to prevent an accidental mixing of both fluids or even filling the brake system with the wrong fluid.
The use of brake fluid approved by AUDI is recommended.
BRAKES
The following tables show the PR number code key. This is important in order to know the brake caliper/brake disc and brake pad combination.
| Brake system | ||||
|---|---|---|---|---|
| Dual-circuit brake system with diagonal distribution and ABS, EBV, EDS, ASR, ESP, ECD and UP |
| Front Wheel Brakes | ||||
|---|---|---|---|---|
| Production-relevant no. (Pr. no.) | 1LT | 1LA | 1LJ | |
| Brake caliper | FN3- 57 16" | FBC-57 16" | FBC-57 17" | |
| Brake disc ventilated | Dia. mm | 314 | 320 | 345 |
| Brake disc, thickness | Mm | 25 | 30 | 30 |
| Brake disc, wear limit | Mm | 23 | 28 | 28 |
| Brake caliper, piston | Dia. mm | 57 | 57 | 57 |
| Pad thickness with backing plate and dampening sheet | Mm | 20.3 | 18.8 | 18.8 |
| Brake pad wear limit with backing plate and dampening sheet | Mm | 7 | 7 | 7 |
| Rear Wheel Brakes | |||
|---|---|---|---|
| Production-relevant no. (Pr. no.) | 1KW | 1KE | |
| Brake caliper | CII-43 EPB (16") | CII-43 EPB (17") | |
| Brake disc | Dia. mm | 300 | 330 |
| Unvented brake disc thickness | Mm | 12 | |
| Internally vented brake disc thickness | 22 | ||
| Brake disc, wear limit | Mm | 10 | 20 |
| Brake caliper, piston | Dia. mm | 43 | 43 |
| Pad thickness with backing plate and dampening sheet | Mm | 17.5 | 17.5 |
| Brake pad wear limit with backing plate and dampening sheet | Mm | 7 | 7 |
The brake system installed in a vehicle is indicated on the vehicle data label by the relevant PR number -A and B-.
Scheme 3
Note. Hairline cracks on brake disc friction surfaces are often observed during brake repairs. Hairline cracks up to 10 mm long are not a technical flaw and are not cause for brake disc replacement. Brake discs with brake pads that have worn through should be replaced.