Antilock Brakes / Traction Control Systems: Service and Repair

When a new master cylinder has been installed or the brake system emptied or partially emptied, fluid may not flow from the bleeder screws during normal bleeding. It may be necessary to prime the system using the following procedure:

1. Using tubing wrench, remove brake lines from master cylinder.
2. Install short brake lines in master cylinder and position them back into reservoir. Ensure short brake line ends are submerged in reservoir brake fluid.
3. Fill reservoir with recommended brake fluid, then cover master cylinder fluid reservoir with shop towel.
4. Pump brakes until clear, bubble-free fluid comes out of both brake lines. If any brake fluid spills on paint, wash it off immediately with water.
5. Remove short brake lines, then reinstall original brake lines.
6. Bleed each brake line at master cylinder using the following procedure:
a. Have assistant pump brake pedal 10 times, then hold firm pressure on pedal.
b. Open rearmost brake line fittings with tubing wrench until stream of brake fluid comes out. Have assistant maintain pressure on brake pedal until brake line fitting is tightened again.
c. Repeat this operation until clear, bubble-free fluid comes out from around tube fitting.
d. Repeat this bleeding operation at front brake line fitting.
7. If any of brake lines or calipers have been removed, it may be helpful to prime system by gravity bleeding. This should be done after master cylinder is primed and bled. To prime system using gravity method, proceed as follows:
a. Fill master cylinder with manufacturer recommended brake fluid.
b. Loosen both rear bleeder screws and leave them open until clear brake fluid flows out. Check reservoir fluid level frequently. Do not allow fluid level to drop below half full.
c. Tighten rear bleeder screws.
d. Loosen bleeder screw on front caliper. Leave open until clear fluid flows out. Bleed front calipers one side at a time.
8. After master cylinder has been primed, lines bled at master cylinder, and the brake system primed, normal brake system bleeding can be resumed at each wheel.