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Home >> Subaru >> 2019 >> WRX Base >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Brake System >> Air Bleeding >> Procedure >> Brake Line

Brake Line

  1. When the master cylinder assembly is replaced or the reservoir tank is empty, bleed the master cylinder assembly before bleeding the brake line. Refer to BRAKE>AIR BLEEDING>PROCEDURE>MASTER CYLINDER .
  2. Fill the reservoir tank of the master cylinder assembly with brake fluid.
    NOTE: While bleeding air, keep the reservoir tank filled with brake fluid to prevent entry of air.
  3. Attach one end of a transparent vinyl tube to the bleeder - screw, and the other end to a brake fluid collection container.
    G08314865Courtesy of SUBARU OF AMERICA, INC.
  4. Loosen the bleeder - screw, and then repeat the full stroke depressing operation of the brake pedal, until brake fluid in the transparent vinyl tube has no more air bubbles.
    NOTE: Air bubbles are removed after repeating the depressing operation 15 times or more for the front caliper, and 20 times or more for the rear caliper.
  5. Perform the steps  2 to  4 above on each brake caliper.
    NOTE:
    • Perform in the order starting from the front RH → front LH → rear LH → rear RH.
    • For brembo type, in the order from inside → outside, bleed air starting from the front RH → front LH → rear LH → rear RH.
  6. Only when replacing the Brembo type brake caliper with a new part, perform the following operations.
    1. Remove the cross spring and pad clip bolt (front only).
    2. Depress and hold the brake pedal with a little force (approx. 5 mm (0.2 in) of pedal stroke).
    3. Loosen the bleeder - screw, and insert the disc brake piston tool between the pad-disc brake outer and the pad - disc brake inner to expand the pad - disc brake outer and the pad - disc brake inner.
    4. Slowly depress the brake pedal with a full stroke, and once the brake pedal reaches the full stroke position, tighten the bleeder - screw in a quick manner and return the brake pedal.
    5. Repeat depressing the brake pedal two or three times.
    6. Repeat steps  2 through  5 until there are no more air bubbles in the transparent vinyl tube.
  7. Tighten the loosened bleeder - screw, repeat firmly depressing of the brake pedal 5 to 6 times, and then depress and hold the brake pedal.
  8. Loosen the bleeder - screw to drain the brake fluid. When the brake pedal reaches the full stroke position, immediately tighten the bleeder - screw and return the brake pedal.
  9. Repeat steps  7 and  8 until there are no more air bubbles in the transparent vinyl tube.
  10. Perform the steps  7 to  9 above on each brake caliper.
    NOTE:
    • Perform in the order starting from the front RH → front LH → rear LH → rear RH.
    • For brembo type, in the order from inside → outside, bleed air starting from the front RH → front LH → rear LH → rear RH.
  11. Operate the hydraulic control unit in the sequence control mode for both ABS and VDC systems.
    CAUTION:
    • If there is a possibility that air enters the pressure control section in the hydraulic control unit, perform steps  12 to  17.
    • For normal air bleeding operation, do not operate the sequence control for the hydraulic control unit. (Operating the sequence control may let air in the normal air bleeding passages move to the pressure control section.)
    NOTE:
    • Normal air bleeding operation does not help bleed air that enters the pressure control section in the hydraulic control unit.
    • If there is a possibility that air enters the pressure control section in the hydraulic control unit (if VDC or ABS operates with air contained in the normal air bleeding passage), perform the sequence control mode for both of the ABS and VDC systems.
  12. Perform the ABS sequence control mode. Refer to VEHICLE DYNAMICS CONTROL (VDC)>ABS SEQUENCE CONTROL .
    CAUTION: Be sure to perform the ABS sequence control mode first.
  13. Perform the air bleeding operation of steps  3 and  4 for the bleeder - screw on each caliper.
    NOTE:
    • Perform in the order starting from the front RH → front LH → rear LH → rear RH.
    • For brembo type, in the order from inside → outside, bleed air starting from the front RH → front LH → rear LH → rear RH.
    • As a reference, the number of the full stroke depressing operation is six times.
  14. Perform the VDC sequence control mode. Refer to VEHICLE DYNAMICS CONTROL (VDC)>VDC SEQUENCE CONTROL .
  15. Perform the air bleeding operation of steps  3 and  4 for the bleeder - screw on each caliper.
  16. Repeat from steps  12 to  15 for three cycles.
  17. In case air still remains at step 16), repeat steps  12 to  15 again until all air is removed.
  18. Fill the reservoir tank with brake fluid up to the "MAX" level.
  19. Tighten the bleeder - screw to the specified torque.

    Tightening torque: 

    Front (except for STI model): 8 N.m (0.8 kgf-m, 5.9 ft-lb)

    Front (STI model): 18.5 N.m (1.9 kgf-m, 13.6 ft-lb)

    Rear (except for STI model): 8 N.m (0.8 kgf-m, 5.9 ft-lb)

    Rear (STI model): 18.5 N.m (1.9 kgf-m, 13.6 ft-lb)

    Rear (electronic parking brake model): 17 N.m (1.7 kgf-m, 12.5 ft-lb)

  20. Install the cap - bleeder to each bleeder - screw.
  21. Check that there are no brake fluid leaks at the flare nut portion or in the entire brake system.
  22. After inspection, wipe off fluid around each bleeder - screw and the reservoir tank.
  23. Perform a road test and ensure that the brakes operate normally.
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