Single-Caliper-Piston System
1. Unscrew the lid from the master cylinder reservoir and siphon out about half of the fluid from the master cylinder with a clean turkey baster. Transfer the siphoned fluid to a small, sealable container and seal the container.
2. Loosen the front wheel bolts with a ratchet and socket, and raise the front of the A4 with a floor jack. Position jack stands under the vehicle’s subframe and lower the A4 onto the jack stands. Remove the wheel bolts and remove the front wheels.
3. Pull the ends of the outer brake pad retainer – the metal spring spanning the rear of the outer brake pad – from the holes in the caliper with needle-nose pliers. Pull the outer brake pad retainer from the caliper and outer brake pad.
4. Pry the rubber caps from the brake caliper guide pins with a small flat-head screwdriver. Loose the caliper guide pins with a ratchet and hex-bit socket, and pull the caliper guide pins from the caliper.
5. Pull the caliper up and off the caliper bracket, and suspend it from the coil spring with a bungee cord. Do not allow the caliper to hang by its rubber hose. Pull the old brake pads off the caliper bracket.
6. Remove the two caliper bracket bolts with a ratchet and socket, and pull the caliper bracket off the front hub.
7. Disengage the rotor retaining screw with a Phillips screwdriver. If the screw will not turn easily, lightly tap the head of it with a hammer to free it. Pull the rotor from the front hub. If the rotor is stuck, lightly tap the rear of it with a rubber mallet to free it.
8. Inspect the front and rear of the rotor for any visual defects, including: deep grooves, signs of grinding, hot spots or mirror-like shine. Replace the rotor with a new one if any defects exist.
9. Set the rotor on the front hub, lining up the screw hole on the rotor with that on the front hub. Tighten the rotor-retaining screw with a Phillips screwdriver.
10. Install the caliper bracket on the front hub and hand-tighten it retaining bolts. Tighten the caliper bracket bolts to 92 foot-pounds with a torque wrench and socket.
11. Set the old inner brake pad in the caliper, so it contacts the caliper piston. Position an 8-inch C-clamp over the caliper, so the fixed part touches the rear of the caliper and the screw part touches the brake pad. Tighten the C-clamp to press the caliper piston into the caliper. Once the C-clamp stops moving, loosen it and remove it and the brake pad.
12. Install new brake pads into the caliper bracket, position the inner brake so the arrow engraved on it points downward.
13. Clean the caliper guide pins with a clean, lint-free cloth and apply a thin coat of new disc brake grease to the smooth part of the caliper guide pin. Insert the guide pins into the caliper and hand-tighten them. Torque the caliper guide pins to 11 foot-pounds with a torque wrench and hex-bit socket.
14. Insert the straight ends of a new outer brake pad retainer – included with the new brake pads – into the small holes on the outside of the caliper. Press the outer brake pad retainer toward the brake pad until it seats in the grooves in the caliper. Press the rubber covers back into place over the caliper guide pins.
15. Repeat Steps 3 through 14 to replace the brakes on the other side of the A4.
16. Reinstall the front wheels on the A4’s hubs and hand-tighten the wheel bolts. Raise the Audi off the jack stands with a floor jack and remove the jack stands. Lower the vehicle to the ground and tighten the lug nuts, in a crisscross pattern, to 89 foot-pounds.
17. Press and release the brake pedal until it feels firm, then check the brake fluid level in the master cylinder reservoir. Add DOT 4 brake fluid to the master cylinder reservoir until the level reaches the “Max” line.
18. Take the old brake fluid in the sealed container to a used-automotive-fluid-recycling center for disposal. Many auto parts stores take old brake fluid free of charge.
Dual-Caliper-Piston System
19. Follow Steps 1 and 2 in the section titled “Single Piston Brake Removal” to remove excess brake fluid, raise the A4 and remove its wheels.
20. Remove the two Torx bolts securing the outer brake pads with a ratchet and Torx-bit socket. Pull the two outer brake pads from the caliper through the hole above each brake pad.
21. Press and hold the button on the brake pad wear sensor wiring harness, and unplug the harness from the A4’s harness. Press the caliper toward the inside of the A4 until it stops moving.
22. Insert a flat-head screwdriver between the topmost brake pad and the caliper carrier’s body, and pry the brake pad toward the rotor to disengage the pad’s retaining clips. Pull the pad from the caliper, through the hole directly above the brake pad. Repeat this step to remove the lower, inside brake pad.
23. Unfasten the caliper carrier retaining bolts with a ratchet and Torx-bit socket. Pull the caliper carrier assembly off the front hub and hang it from the strut spring with a bungee cord. Never allow the caliper to hang by its rubber hose, as this can cause severe damage.
24. Remove, inspect and reinstall the front rotor by following Steps 7 through 9 in the section titled “Single Piston Brake Removal.”
25. Set the caliper carrier back into place on the front hub and hand-tighten the caliper carrier retaining bolts. Torque the caliper carrier retaining bolts to 148 foot-pounds with a torque wrench and Torx-bit socket.
26. Slide the upper inner brake pad into the upper inside hole in the caliper carrier. Line up the fingers on the rear of the brake pad with the caliper piston and press the pad toward the piston until the fingers insert fully into the caliper piston – use extreme care not to puncture the dust boot around the piston. Repeat this step on the lower inner brake pad.
27. Plug the brake pad wear sensor into the A4’s wiring harness.
28. Press the caliper carrier outward until it stops moving. Slide the upper outer brake pad into the caliper carrier and hand tighten its retaining bolt. Slide the lower outer brake pad into the caliper and hand-tighten its retaining bolt. Torque the brake pad retaining bolts to 18 foot-pounds with a torque wrench and Torx-bit socket.
29. Repeat Steps 2 through 10 to replace the brakes on the other side of the A4.
30. Reinstall the front wheels, pressurize the brake system and refill the brake master cylinder by following Steps 16 through 18 in the section titled “Single Piston Brake Removal.”
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