The brake fluid should be replaced at least every 3 years or 45,000 miles (72,000 km).
The purpose of bleeding the brakes is to expel air trapped in the hydraulic system. The system should be checked for fluid condition, brake hose condition and air whenever the pedal feels spongy. The system must be bled whenever it has been opened, repaired, or a hydraulic component replaced. If you are not using a pressure bleeder, you will need an assistant for this job.
If the ABS modulator has been opened or replaced it may be necessary to bleed each line at the modulator unit.
When bleeding the brakes, air may be trapped in the brake lines or valves far upstream, as much as 10 feet from the bleeder screw. Therefore, it is very important to have a fast flow of a large volume of brake fluid when bleeding the brakes, to make sure all of the air is expelled from the system.
Proper manual bleeding of the hydraulic brake system will require the use of an assistant unless a suitable self-bleeding tool is available. If using a self-bleeding tool, refer to the manufacturer's directions for tool use and follow the proper bleeding sequence listed in this section.
- To bleed the brakes, if the ABS modulator has not been opened or replaced, proceed as follows.
If the master cylinder reservoir runs dry during the bleeding process, restart from the first fitting.
- Remove the old brake fluid and clean the brake master cylinder reservoir with a clean lint-free cloth.
Bleed the brake system at each fitting. Do not proceed to the next fitting until all air bubbles are removed from the previous fitting. Bleed the brakes, making sure to following this sequence:
- Attach a clear plastic hose to the bleeder screw, then place the hose into a clean jar that has enough fresh brake fluid to submerge the end of the hose.
- Have an assistant pump the brake pedal 3-4 times, and hold pressure on it, then open the bleeder screw at least 1 / 4 turn. When the bleeder screw opens, the brake pedal will drop. Have the assistant hold it there until the bleed valve is closed.
- Close the bleeder screw and have the assistant slowly release the brake pedal only AFTER the bleeder screw is closed, then check the master cylinder fluid level and top off as necessary.
- Repeat the bleeding procedure until all there are no air bubbles, or a minimum of 4 or 5 times at each bleeder screw, then check the pedal for travel and feel. If the pedal travel is excessive, or feels spongy, it's possible enough fluid has not passed through the system to expel all of the trapped air.
Constantly check and top off the master cylinder. Do not allow the master cylinder to run dry, otherwise air will re-enter the brake system.
- Once completed, test drive the vehicle to be sure the brakes are operating correctly and that the pedal feel is firm.
See Figures 1, 2 and 3