GM Prizm/Nova 1985-1993 Repair Guide

Bleeding the Brake System

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See Figure 1

On vehicles equipped with ABS, the hydraulic modulator must be bled prior to the brake calipers and wheel cylinders. For complete ABS bleeding, refer to Anti-Lock Brakes at the end of this Section.

It is necessary to bleed the hydraulic system any time system has been opened or has trapped air within the fluid lines. It may be necessary to bleed the system at all 4 brakes if air has been introduced through a low fluid level or by disconnecting brake pipes at the master cylinder.

If a line is disconnected at 1 wheel only, generally only that brake needs bleeding. If lines are disconnected at any fitting between the master cylinder and the brake, the system served by the disconnected pipe must be bled.


WARNING
Do not allow brake fluid to splash or spill onto painted surfaces; the paint will be damaged. If spillage occurs, flush the area immediately with clean water.

  1. Fill the master cylinder reservoir to the MAX line with brake fluid and keep it at least half full throughout the bleeding procedure.
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  3. If the master cylinder has been removed or disconnected, it must be bled before any brake unit is bled. To bleed the master cylinder:
    1. Disconnect the front brake line from the master cylinder and allow fluid to flow from the front connector port.
    2.  
    3. Reconnect the line to the master cylinder and tighten it until it is fluid tight.
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    5. Have a helper press the brake pedal down one time and hold it down.
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    7. Loosen the front brake line connection at the master cylinder. This will allow trapped air to escape, along with some fluid.
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    9. Again tighten the line, release the pedal slowly and repeat the sequence (steps c-d-e) until only fluid runs from the port. No air bubbles should be present in the fluid.
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    11. Final tighten the line fitting at the master cylinder to 11 ft. lbs.
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    13. After all the air has been bled from the front connection, bleed the master cylinder at the rear connection by repeating steps A-E.
    14.  

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  5. Place the correct size box-end or line wrench over the bleeder valve and attach a tight-fitting transparent hose over the bleeder. Allow the tube to hang submerged in a transparent container of clean brake fluid. The fluid must remain above the end of the hose at all times, otherwise the system will ingest air instead of fluid.
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Fig. Fig. 1: Brake bleeding

  1. Have an assistant pump the brake pedal several times slowly and hold it down.
  2.  
  3. Slowly unscrew the bleeder valve ( 1 / 4 - 1 / 2 turn is usually enough). After the initial rush of air and fluid, have the assistant slowly release the brake pedal. When the pedal is released, tighten the bleeder.
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  5. Repeat Steps 4 and 5 until no air bubbles are seen in the hose or container. If air is constantly appearing after repeated bleedings, the system must be examined for the source of the leak or loose fitting.
  6.  
  7. If the entire system must be bled, begin with the right rear, then the left front, left rear and right front brake in that order. After each brake is bled, check and top off the fluid level in the reservoir.
  8.  


WARNING
Do not reuse brake fluid which has been bled from the brake system.

  1. After bleeding, check the pedal for sponginess or vague feel. Repeat the bleeding procedure as necessary to correct.
  2.  

 
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