Document 2JdmbgKG4DoeZ3oBE6x6bdyM6

BRAKE SYSTEM SERVICE BRAKE SYSTEM BLEEDING LESSON ONE-MODULE 2 Air Trapped in Brake Line BSR049-A Item 1 Brake Line Description Item Description 2 Trapped Air As you have learned, hydraulic fluid is not compressible, but air trapped in a hydraulic system is. Bleeding is the technique used to remove trapped air from a brake system. Brakes need to be bled whenever a hydraulic component of the brake system is replaced, or whenever your diagnosis indicates that air is trapped in the hydraulic system. Methods of bleeding brakes will vaiy with the type of system you are working on. The reason that the brakes are being bled will also influence the method. If you have a vehicle that has a spongy pedal, you should bleed the entire brake system. If you had to replace a single wheel cylinder, the other wheel on that hydraulic circuit is all that will require bleeding. The bleeding procedure will also vary depending on whether you are bleeding a front/rear split brake system or a diagonally split brake system. If you replace the right rear wheel cylinder on a diagonally split brake system, bleeding the left rear wheel will not remove air from the affected hydraulic circuit. In this situation you would want to bleed the left front wheel to be sure all the air is removed from the affected circuit. If you were working on a front/rear split system, than you would want to bleed the right rear wheel cylinder. Brake System Diagnosis and Repair September, 2005 65