Brake hydraulic system — bleeding
Warning: Wear eye protection when bleeding the brake system. If the fluid comes in contact with your eyes, immediately rinse them with water and seek medical attention.
Note: Bleeding the hydraulic system is necessary to remove any air that manages to find its way into the system when it’s been opened during removal and installation of a hose, line, caliper or master cylinder.
1. You’ll probably have to bleed the system at all four brakes if air has entered it due to low fluid level, or if the brake lines have been disconnected at the master cylinder or ABS hydraulic actuator.
2. If a brake line was disconnected only at a wheel, then only that caliper or wheel cylinder must be bled.
3. If a brake line is disconnected at a fitting located between the master cylinder and any of the brakes, the entire system must be bled. And, if the master cylinder has run dry or has been replaced, bleed the master cylinder as described in Master cylinder — removal, installation and reservoir/grommet replacement, Step 17, followed by the remainder of the system.
4. Remove any residual vacuum from the brake power booster by applying the brake several times with the engine off.
5. Remove the master cylinder reservoir cap and fill the reservoir with brake fluid. Reinstall the cap.
Note: Check the fluid level often during the bleeding operation and add fluid as necessary to prevent the fluid level from falling low enough to allow air bubbles into the master cylinder.
6. Have an assistant on hand, as well as a supply of new brake fluid, a clear plastic container partially filled with clean brake fluid, a length of clear tubing to fit over the bleeder valve and a wrench to open and close the bleeder valve.
7. Beginning at the right rear wheel, loosen the bleeder valve slightly, then tighten it to a point where it’s snug but can still be loosened quickly and easily.
8. Place one end of the tubing over the bleeder valve and submerge the other end in brake fluid in the container (see illustration). 9. Have the assistant depress the brake pedal slowly and hold the pedal down firmly.
i. 8 When bleeding the brakes, a hose is connected to the bleed screw at the caliper or wheel cylinder and then submerged in brake fluid — air will be seen as bubbles in the tube and container (all air must be expelled before moving to the next wheel)
10. While the pedal is held down, open the bleeder valve just enough to allow a flow of fluid to leave the valve. Watch for air bubbles to exit the submerged end of the tube. When the fluid flow slows after a couple of seconds, close the valve and have your assistant release the pedal.
11. Repeat Steps 9 and 10 until no more air is seen leaving the tube, then tighten the bleeder valve and proceed to the left rear wheel, the right front wheel and the left front wheel, in that order, and perform the same procedure. Be sure to check the fluid in the master cylinder reservoir frequently.
Warning: Brake fluid is «Hydroscopic» meaning: Brake fluid will mix with water and can absorb moisture from the surrounding air. Always use brake fluid from a sealed container and never one that has been on a shelf for any length of time. Brake fluid can gain (on average) about 4% water per year. Under the extreme pressures in a brake system as well as the heat developed, the moisture in the brake fluid can actually boil which can leave you with brake fade or loss of functioning brakes entirely. Most manufacturers recommend that the brake fluid should be flushed out and replaced every 3 to 5 years.
12. Refill the master cylinder to the MAX level with fluid at the end of the operation.
13. Check the operation of the brakes. The pedal should feel solid when depressed, with no sponginess. If necessary, repeat the entire process.
Warning: Do not operate the vehicle if the ABS light or BRAKE light fails to go out, if the brakes feel low or spongy, or if you have any doubts as to the effectiveness of the brake system.