When replacing certain brake components or after a brake component failure, it is often necessary to bleed, or remove the air from a hydraulic brake system. With air in the lines, the brakes will feel spongy and will not have adequate stopping power. Eventually, too much air in the lines can cause brake failure. Brake bleeding requires following some specific procedures and requires some specific tools to speed the job.
Examine the brake bleeding sequence. This can be obtained from an auto parts store, the vehicle shop manual or your local dealer service department. It is critical that the bleeding sequence for each wheel be followed, as this resets the proportioning valve. This is what gives equal pressure to both front and rear brakes. Usually, the sequence starts with the furthest wheel from the master cylinder, or the passenger side rear tire, then the driver side rear, passenger side front and then the driver side front.
Fill the bleeder bottle part way with fluid, and attach the hose to the brake bleeder valve. If you do not have an assistant, you will need a self-bleeder kit, available at auto parts stores. Using the small wrench, open the valve. Pump the brakes until there are no more air bubbles in the line going to the bottle. Then close the bleeder screw before removing the hose so that no air reenters the system. Follow this procedure in sequence for every wheel, even if only one component was replaced.
Use a vacuum pump to bleed the brakes if you have an assistant. Fill the bottle on the vacuum pump partway with fluid. Attach the hose to the bleeder screw. Pump the vacuum pressure up and have your assistant pump the brake pedal several times and then hold it. Open the bleeder valve, allowing the vacuum pump to suck the brake fluid and air from the bleeder. Repeat this procedure until no air bubbles are seen in the line between the vacuum pump and the bleeder screw. Tighten the bleeder screw and then remove the hose so that no air reenters the system. Repeat this process for each wheel in order.
Check the brakes. If after through bleeding in sequence, the brakes do not work properly and air is found in the system, then there is a leak somewhere. Check all brake line connections first, including copper washers on calipers and wheel cylinders. Then check brake lines and hoses for dampness and leaks. Once the leak is found, replace the leaking washer, line or hose or component.
