Brake bleeding on a vehicle is a mechanical process that removes air from the brake fluid in the hydraulic system when repairing brakes or performing brake maintenance; the term does not typically describe a problem that needs to be fixed. Bleeding a brake system is typically required when the brake fluid is low, resulting in squishy or soft braking typically associated with a leak that has drained brake fluid from the system.
When the brake pedal is depressed and the car does not stop quickly, or at all, it is often because of a lack of fluid or an excess of air bubbles in the system's hydraulic fluid. Check the brake fluid reserve mounted next to the master cylinder under the vehicle's hood in the engine compartment. If the level is low, add additional fluid to bring the level to the indicated amount. If the level drops again, then there is a leak in the brake system.
After adding brake fluid or a brake fluid leak repair, bleed the air from the system. Open one of the brake bleed screws located behind each wheel. Attach a small hose or tube over the bleed screw and put the other end in a container to catch the fluid. Have an assistant slowly pump the brake pedal until all of the air bubbles squirt out of the fluid catch hose.
When there are no more bubbles, have your assistant hold the pedal to the floor while you tighten the screw so air does not get sucked back into of the system. Repeat the process for all four wheels and fill the brake fluid to the full line in the reservoir.