Audi Cars 1999-05

Brake Caliper

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Overhaul




WARNING
If the vehicle is equipped with the Electronic Stability Program (ESP), the ESP pump must be actuated during the bleeding procedure, using a proper scan tool, such as VAG 1551, VAG 1552, or equivalent, capable of activating the ESP pump.

To overhaul the brake caliper, the brake caliper piston must be removed.

There are 2 different ways to remove the piston from the caliper. It can be pumped out using the foot brake or removed using compressed air.

When removing a brake caliper piston using the foot brake:



Only one caliper can be overhauled at a time
 
The piston is pumped out before the brake line is loosened or disconnected
 
This procedure takes more time than the compressed air method, however if the caliper piston is severely seized, compressed air may not be able to move the piston. Therefore pressing the piston out hydraulically may be the only option short of replacing the caliper assembly.
 
This method requires the brakes to be bled every time a hydraulic line is opened.
 

If the brake caliper piston moves relatively freely, removing the piston with compressed air works well and is much less time consuming than other methods.


CAUTION
NEVER place your fingers in front of the pistons in an attempt to catch or protect the pistons when applying compressed air. This could result in personal injury!

  1. To remove the piston via compressed air:
  2.  
    1. Remove the caliper from the vehicle and place on a clean workbench.
    2.  
    3. Stuff a shop towel or a block of wood into the caliper to catch the piston.
    4.  
    5. Remove the caliper piston using compressed air applied into the caliper inlet hole. Inspect the piston for scoring, nicks, corrosion and/or worn or damaged chrome plating. The piston must be replaced if any of these conditions are found.
    6.  

  3. To remove by being pumped out using the foot brake:
  4.  
    1. Work with one caliper at a time:
    2.  
    3. Do NOT disconnect or loosen the brake hose, otherwise the brake will have to be bled.
    4.  
    5. Place a suitable drain pan under the brake caliper.
    6.  
    7. Remove one brake caliper and place over the drain pan.
    8.  
    9. Press the brake pedal down fully and release the brake pedal slowly, then check the fluid level in the master cylinder reservoir. If the reservoir runs dry, the brake system will have to be bled.
    10.  
    11. Repeat the above step until the caliper piston is dislodged. Some brake fluid will leak out once the piston is dislodged.
    12.  
    13. Disconnect the caliper fluid line.
    14.  
    15. Inspect and overhaul the caliper if possible, otherwise replace it.
    16.  
    17. Reinstall the overhauled or replacement brake caliper completely and bleed the brakes as outlined in this section.
    18.  
    19. Repeat the above steps for each caliper that is to be disassembled.
    20.  




Click image to see an enlarged view

Fig. Use compressed air to drive the piston out of the caliper, but make sure to keep your fingers clear



Click image to see an enlarged view

Fig. Withdraw the piston from the caliper bore



Click image to see an enlarged view

Fig. Use extreme caution when removing the piston seal; Do NOT scratch the caliper bore

To overhaul:

  1. Remove the piston seals from the groove in the caliper bore.
  2.  
  3. Carefully loosen the brake bleeder valve cap and valve from the caliper housing.
  4.  
  5. Clean all parts with an approved brake cleaner or isopropyl alcohol and dry with compressed air.
  6.  
  7. Inspect the caliper bores, pistons and mounting threads for scoring or excessive wear.
  8.  
  9. Use crocus cloth to polish out light corrosion from the piston and bore.
  10.  
  11. If the caliper piston is damaged, severely scored, or out of round, if available, replace the piston, otherwise replace the caliper assembly.
  12.  
  13. Make sure all components are thoroughly cleaned. The brake caliper piston and bore must be free of all debris. If the upper or lower seal groves in the caliper bore have any built up rust or debris, obtain a small wire brush from a hobby supply store that will fit into a small die grinder or similar tool, and thoroughly clean the grooves. Flush the caliper body thoroughly with an approved brake cleaner or isopropyl alcohol.
  14.  
  15. Lubricate and install the bleeder valve and cap.
  16.  
  17. Pour a small amount of fresh brake fluid into a clean container and saturate the new seals with brake fluid. Then, install the seals into the caliper bore grooves, making sure they are fully seated and not twisted.
  18.  
  19. Lubricate the following with an approved high temperature brake-cylinder paste, such as G 052 150 A2:
  20.  


    The brake caliper piston bore
     
    The outer circumference of the brake caliper piston
     
    The dust cover/sealing cover
     

  21. Install the dust cover/sealing cover around the bottom of the piston.
  22.  
  23. Seat the dust cover/sealing cover lip into the upper groove of the caliper bore.
  24.  
  25. Once the dust cover/sealing cover is fully seated in the caliper bore, press the piston into the caliper bore slowly and evenly. Do NOT tilt, or force the piston into the bore. While pressing the piston into the bore, if necessary, slide the upper portion of the dust cover/ sealing cover upward to prevent it from bunching up. Make sure to seat the upper lip of the cover around the brake piston before the piston is completely installed in the caliper bore.
  26.  
  27. Inspect and if necessary, install new guide bushing sleeves at the slides.
  28.  
  29. Install the caliper on the vehicle and properly bleed the brake system as outlined in this section.
  30.  
  31. Install the wheels and hand tighten the lug bolts. Lower the vehicle carefully until the tires begin to contact the surface and torque the lug bolts to specification in a crisscross pattern to:
  32.  


    M12 x 1.5 lug bolts: 81 ft. lbs. (110 Nm)
     
    M14 x 1.5 lug bolts: 89 ft. lbs. (120 Nm)
     



WARNING
Failure to properly torque the wheels to the correct torque using the proper sequence could cause a brake pulsation and rotor warpage.

  1. Press the brake pedal down slowly about 2 inches (50mm), then slowly release. Continue to press and release the brake pedal in slow even 2-inch (50mm) strokes until the pedal is firm.
  2.  

Removal & Installation




WARNING
If the vehicle is equipped with the Electronic Stability Program (ESP), the ESP pump must be actuated during the bleeding procedure, using a proper scan tool, such as VAG 1551, VAG 1552, or equivalent, capable of activating the ESP pump.

  1. Block the rear wheels and apply the parking brake.
  2.  
  3. Loosen the front wheel bolts 1 / 8 turn.
  4.  
  5. Raise and support the vehicle. Remove the front wheels.
  6.  
  7. If equipped, disconnect the brake pad wear sensor from the harness.
  8.  


NOTE
Do NOT loosen or disconnect the brake caliper fluid hose if the caliper is being removed to access or replace another component. Loosen and disconnect the fluid hose only if the caliper is to be replaced, completely removed or overhauled. If the fluid hose is to remain attached to the caliper, support the caliper assembly with mechanic's wire to avoid damaging the line.

  1. If the caliper is to be completely removed from the vehicle (replaced disassembled or overhauled):
  2.  
    1. Siphon the brake fluid out of the reservoir and fix the brake pedal in the depressed position. Or, remove the reservoir cap and place a thin sandwich bag over the opening, then reinstall the cap without the fluid level float to captivate the system. This will prevent brake fluid from draining out of the brake lines while the line is disconnected from the caliper.
    2.  
    3. Using a flare nut wrench, loosen, but Do NOT disconnect the flexible line to the caliper.
    4.  

  3. On single piston Teves/ATE® calipers;
  4.  
    1. Using a suitable prytool, carefully remove the tensioning spring.
    2.  
    3. Remove the 2 plastic plugs from the caliper slide bolts and using a 7mm hex tool, remove the slider bolts.
    4.  

  5. On Lucas® calipers;
  6.  
    1. Hold the flats of the pin sliders with an open end wrench. A thin open-end wrench may be required.
    2.  
    3. Remove the upper and lower pivot bolts.
    4.  

  7. If necessary, to clear a wear ridge on the outer circumference on the brake rotor, rock the caliper assembly side-to-side several times and then carefully remove the caliper, and if attached, the inner brake pad.
  8.  
  9. If the brake fluid line is to be removed from the caliper, place a suitable drain pan under the caliper, disconnect and plug the fluid line and the caliper. Note, to avoid damage to the flexible brake line, hold the brake line with a flare nut wrench and spin the brake caliper. If the brake line is sealed to the caliper with a crush washer, replace the crush washer with the appropriate replacement part.
  10.  
  11. If the brake caliper mounting bracket is to be removed, remove the caliper bracket-to-knuckle mounting bolts and lift off the bracket. These mounting bolts typically require a sturdy 6-point 16mm socket.
  12.  


NOTE
The brake caliper bracket-to-steering knuckle bolts may require a significant amount of effort to loosen. Use a proper fitting 6-point 1 / 2 inch drive metric impact socket and sturdy breaker bar to loosen the mounting bolts.



Click image to see an enlarged view

Fig. The brake caliper mounting bracket is attached to the steering knuckle. The brake caliper is attached to the mounting bracket-Teves/ATE® caliper shown

To install:

  1. If the brake fluid line was disconnected, connect the brake line to the caliper and torque to 10 ft. lbs. (14 Nm). Note, to avoid damage to the flexible brake line, hold the brake line with a flare nut wrench and spin the brake caliper. If the brake line is sealed to the caliper with a crush washer, replace the crush washer with the appropriate replacement part.
  2.  
  3. On single piston brake calipers, if the caliper bracket was removed
  4.  
    1. Support the caliper temporarily with mechanic's wire taking care to not damage the flexible brake hose.
    2.  
    3. Install the bracket on the knuckle and torque the bolts to:
    4.  


      1990-97 Passat models: 92 ft. lbs. (125 Nm).
       
      1998-00 Passat models: 89 ft. lbs. (120 Nm).
       
      A4 models: 92 ft. lbs. (125 Nm).
       

    5. Install the brake pads in the caliper bracket as outlined in this section.
    6.  
    7. Lower the brake caliper over the brake pads and check that the pad springs are correctly seated.
    8.  

  5. On Lucas® brake calipers, install a new bolt and torque to:
  6.  


    1990-97 Passat models: 26 ft. lbs. (35 Nm)
     
    1990-97 Passat models: 22 ft. lbs. (30 Nm)
     
    A4 models: 22 ft. lbs. (30 Nm)
     

  7. On Teves/ATE® Brake calipers:
  8.  
    1. Lubricate the slider bolts with approved brake grease.
    2.  
    3. Install the slider bolts and torque to 18 ft. lbs. (25 Nm).
    4.  
    5. Install the protective caps and the retainer spring.
    6.  

  9. On Teves/ATE® brake 2-piston, 4-pad calipers:
  10.  
    1. Install the brake caliper and torque to 148 ft. lbs. (200 Nm).
    2.  
    3. Install the brake pads; replace the outer pad retainers and torque to 18 ft. lbs. (25 Nm).
    4.  

  11. If equipped, connect the brake wear sensor wire to the harness. Check for a good connection as most problems with the sensor circuit are caused by faulty connections. Check that the wire is held by the loop in the dust cover and the connector is held at the clips.
  12.  
  13. If disconnected install the brake hydraulic lines and torque to:
  14.  


    Compression fittings: 11 ft. lbs. (15 Nm)
     
    Banjo bolts (use new crush washers): 22 ft. lbs. (30 Nm)
     

  15. Clip the brake fluid line into the holder.
  16.  
  17. If the brake fluid line was disconnected, bleed the brake system as outlined in this section.
  18.  
  19. Install the wheels and hand tighten the lug bolts. Lower the vehicle carefully until the tires begin to contact the surface and torque the lug bolts to specification in a crisscross pattern to:
  20.  


    M12 x 1.5 lug bolts: 81 ft. lbs. (110 Nm)
     
    M14 x 1.5 lug bolts: 89 ft. lbs. (120 Nm)
     



WARNING
Failure to properly torque the wheels to the correct torque using the proper sequence could cause a brake pulsation and rotor warpage.

  1. Press the brake pedal down slowly about 2 inches (50mm), then slowly release. Continue to press and release the brake pedal in slow even 2-inch (50mm) strokes until the pedal is firm.
  2.  


NOTE
Procedures may vary slightly, depending on vehicle or brake type. Refer to appropriate illustration for additional assistance.

  1. Before servicing the vehicle, refer to the precautions section.
  2.  
  3. Remove the wheels.
  4.  
  5. Loosen the hydraulic line at the caliper, then remove the caliper from the carrier. With guide pin calipers, be sure to hold the pin with a back-up wrench when removing the caliper bolts.
  6.  
  7. Remove the caliper from the hydraulic line.
  8.  
  9. The carrier can be removed by removing the 2 bolts.
  10.  

To install:

  1. If removed, install the carrier. Torque the carrier bolts to 92 ft. lbs. (125 Nm).
  2.  
  3. Thread the caliper onto the hydraulic line and hand-tighten it. Fit the caliper into place on the carrier.
  4.  
  5. Torque the caliper bolts (guide pins) as follows:

    On TT models: 21 ft. lbs. (28 Nm)
     
    On A4 and A6 models with FN3 type brakes: (25 Nm)
     
    On All A3 models, A4 and A6 models with FNR-G60 type brakes: (30 Nm)
     
    On A6 models with HP2 (aluminum caliper) type brakes: (190 Nm)
     
    On A6 models with 18- Brembo type brakes: (110 Nm)
     

  6.  
  7. Torque the brake line connection to (15 Nm).
  8.  
  9. Tighten the hydraulic line and bleed the brakes.

    Click image to see an enlarged view

    Fig. Exploded view of front brake components-TT models



    Click image to see an enlarged view

    Fig. Exploded view of FN3 type front brake components-A4 and A6 shown



    Click image to see an enlarged view

    Fig. Exploded view of C54 type front brake components-A4 models



    Click image to see an enlarged view

    Fig. Exploded view of HP-2 type (aluminum caliper) front brake components-A6 shown; others similar



    Click image to see an enlarged view

    Fig. Exploded view of FNR-60 type front brake components-A4 and A6 shown



    Click image to see an enlarged view

    Fig. Exploded view of Brembo 18- type front brake components-A6 shown; others similar

  10.  

 
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