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Brake Maintenance - How to Change Brake Pads and/or Rotors

If you are going to work on the rear brakes, it is recommended that you use a special tool that retracts the piston into the caliper.  You can't simply press on the piston like wiith older cars, or like you can on the front brakes.  This is due to the design of the electric parking brake motor, which engages the disc brake when you set the parkig brake.  To get the pads to retract you can get a special tool from MacTools, or you can use the more sophisticated  Vag-Com software and cable from Ross-Tech - more info here

General Procedure:  

  1. Remove the decorative hub cap – using the special tool from the trunk.
  2. Break loose wheel lug nuts, using tire iron or 17mm lug wrench.   It’s easiest to do this with the car still on the ground.
  3. Jack up car and support with jack stand.  For front wheels – if you can’t place a jack stand at the standing seam, try placing it under the connection between the lower wishbone and chassis (about 1 foot inside the wheel). 
  4. Remove the lug nuts and wheel.
  5. Unscrew the filler cap from the brake fluid reservoir, and place towels around the reservoir to catch any brake fluid that may overflow the reservoir. Brake fluid is very corrosive, so you don't want to get any on the car's paint finish.
  6. If working on the rear brakes, now is a good time to retract the electric parking brake using VCDS (see below for procedure).
  7. For front left wheel, with brake pad sensor - remove brake pad sensor:
    1. The wire is routed under two retainers – note how it is routed, and then remove the wire from the retainers.
    2. Grab the sensor end with pliers and pull out from the brake pad, and let dangle.
    3. Disconnect the sensor wire assembly from the car.  First remove the connector from the mounting bracket – pull back the plastic snap latch tab, rotate the connector 90 degrees, and the connector assembly can then be removed form the bracket.  Then unplug the sensor from the brake pad – use a small screwdriver to pry the snap latch apart and the two halves can then be disconnected.
  8. Remove caliper from rotor:
    1. Fronts brakes only: remove the anti-rattle spring – you can pry one leg off the caliper with a screw driver and the spring will pop off.
    2. Loosen and remove the two bolts on the inboard side of the caliper using a 13 mm socket.  For the rears, use a 15mm open crescent wrench to keep the securing nut from turning.
    3. Pry back the rear brake pad away from the rotor – use a screwdriver to pry it back until you can see daylight between the pad and rotor.
    4. Remove the caliper from the caliper carrier – you may need to rock it back and forth a bit.
    5. Support the caliper so that its weight is not carried by the brake hose.
  9. Remove and replace the rotor and caliper carrier (Warning – this procedure applies t the fronts only – I have not personally removed the rear brake rotor):
    1. Remove caliper carrier – two 21mm bolts.  You’ll need a breaker bar for this. Remove the T-30 torx screw that secures rotor to hub.
    2. The rotor should come off pretty easily, but you may need to knock it with a hammer to break loose any corrosion between the aluminum rotor “hat” and the wheel hub
    3. .Inspect the wheel hub, and sand off any rust deposits.  It is critical that the hub surface be absolutely flat and clear of debris, so that the new rotor sits flat and turns without wobbling. 
    4. Before installing the new rotor first wash it with soap and water to remove any degreaser or other contaminants from the factory.  You may notice that the rotor starts to turn rust colored - this is a good thing, as it means you've succeeded in removing the protectant coating.  Some people advocate using brake cleaner on the rotor surface as well.
    5. Installation of the new rotor is the reverse process.  Apply anti-sieze compound to the hub, then place rotor on hub and secure with torx screw.   Do not over-tighten the torx screw.
    6. Re-attach caliper carrier bracket – torque about 100 lb-ft
  10. Remove the old pads from brake caliper.  For the fronts the inside pad is held to the brake piston with spring clips – you should be able to pull it right out.  The outboard pad is held to the caliper surface via the sticky back of the caliper - pry it loose and remove.  For the rears both inside and outside pads ride in a set of spring metal clips and you can just pry them out quite easily.
  11. The caliper piston needs to be pressed back into the caliper housing so that it is flush and the new, thicker pads will clear the rotor.  You can use a large C clamp to force it back – it is handy to use the old pad as a surface to press against.  When the piston moved back it will cause some brake fluid to be forced back into the reservoir, so be careful that any spillage from the reservoir is caught by the towels that you placed in step 5.
  12. Place new pads into the caliper:
    1. For the inboard pad - first apply anti-squeal compound to the rear of the inboard pad, in the area where it will contact the face of the caliper piston, then insert the spring clips into the brake piston.
    2. For the  new outboard pad, remove the paper from the sticky side, and position the pad in the caliper
    3. Apply anti-squeal compound to the mounting “notches” at top and bottom of the two pads (where they will ride on the caliper carrier pins.
  13. Place the caliper with new pads installed back over the rotor and onto the caliper carrier.  The bolt carrier on the calipers may interfere with the mating female threaded part on the caliper carrier – you can pull back on these so that there is adequate room to clear.
  14. One the caliper is properly positioned, apply lubricant to the threads of the retaining bolts, then insert the bolts and tighten.
  15. Left front wheel sensor wire: connect the new sensor wire assembly, snap the connector into the bracket, route the wire into the retainer(s), and finally insert the sensor into the inside brake pad – it should snap into place.
  16. For fronts - reinstall the anti-rattle spring. 
  17. Remount wheel and secure with lug bolts.
  18. Remove jack stand(s) and lower car.
  19. Torque the lug bolts to 90 ft-lbs.
  20. Reinstall the hub cap.
  21. Take the car out for a test drive, and bed the new pads.  Be sure to follow the specific procedures of the hbrake pad manufactrurer.  To bed stock pads:
    1. Find a deserted road where you can safely accelerate and brake without coming to a stop
    2. Accelerate to 60 MP, then brake hard to 30 MPH, but no so hard as to engage ABS.  Do this 5 or 6 times in succession
    3. Then let the brakes cool by driving for 3-4 minutes without touching the brakes
    4. Repeat step B
    5. Cool the brakes with 10 minutes of steady driving, without using the brakes
    6. Then drive home and park without setting the parking brake.  Let the car sit overnight

 

Quick Guide to Using VCDS to Retract Rear Electric Parking Brake:

  1. Boot PC, then connect VCDS cable using USB connector.
  2. Connect OBD plug to car.  Should get green light on connector.
  3. Turn ignition switch in – don’t start car, but dashboard lights should come on.
  4. Start VCDS application. 
  5. Check for proper connection between VCDS and car:
    1. Options > Select Port> USB
    2. Then “Test.”  If OK, click “OK.”  The “Save” to apply configuration.  Return to main menu
  6. Run Autoscan.  You may want to save results in a log file.
  7. Retract rear electric parking brake:
    1. Select > 53-Parking Brake >Basic Setup -04 > Group 7, GO!
    2. EPB should retract
    3. Done, Go Back
  8. Now OK to work in rear brakes – close down VCDS application, turn off ignition, disconnect OBD connector from car.
  9. When finished working on rear brakes, restart VCDS and connect to car, then close EPB Select > 53-Parking Brake >Basic Setup -04 > Group 6, GO!
  10. Also try cycling EPB: Select > 53-Parking Brake >Basic Setup -04 > Group 10, GO!