How to Bleed Brakes After Installing a Brake Wheel Cylinder

Component replacement can be difficult when repairing a brake hydraulic system, but the job is not complete until all the air has been purged from the new part. Air may have also been introduced to any point in the system hydraulically linked to the replaced cylinder. Domestic vehicles are usually plumbed with the rear brake system isolated from the front brake hydraulics. Some Asian cars and most European models link one front and one rear brake. These plumbing methods prevent total system failure if a brake line ruptures. In that case, the intact portion of the system still functions. You need only bleed the portion of the system that was opened during the cylinder replacement.

Instructions

1

Remove the master cylinder reservoir cover, or lid, and fill the reservoir to the maximum fill level with new brake fluid. Open the bleeder screw of the new wheel cylinder a half-turn, using a line wrench. Monitor the fluid level in the reservoir while allowing gravity to force fluid into the opened wheel cylinder.

2

Close the bleeder screw when fluid begins exiting the screw. Check the fluid level in the master cylinder reservoir throughout the bleeding process. Force one end of the rubber hose onto the wheel cylinder bleed screw and place the other end in a clear, clean bottle or jar. Add enough brake fluid to the clear container to keep the hose end submerged.

3

Have an assistant depress the brake pedal firmly while you open the bleed screw. The brake pedal should sink to the floor when the screw is opened. Close the screw, then have your assistant release the brake pedal. Continue in this manner until air bubbles are no longer seen leaving the submerged hose end. Repeat this process at the other wheel cylinder, or whatever component is hydraulically linked to the wheel cylinder that was replaced.