Document pGZedR42DrvQVRy389qEmVQ7

BRAKE SYSTEM DIAGNOSIS AND TESTING LESSON ONE-MODULE 1 Brakes Lock Up (Grabbing) An anti-lock brake system (ABS) prevents the wheels from locking up. If the customer states that the brakes lock up and the vehicle is equipped with ABS, it is possible that the anti-lock brakes are not operating properly. Brake lock up may be caused by: Early morning dew on the pads or shoes. Incorrect tire pressure. Worn tires. Glazed brake shoes or pads. Grease or fluid on the brake shoes or pads. Faulty brake pressure control valve (proportioning valve). Brakes Lock Up Diagnosis To determine the cause of grabbing brakes, perform the following tests: Warm up the brakes to remove morning dew. Check the tires for excessive wear and improper pressure. Inspect the brake shoes and/or pads for glazing, grease or fluid contamination, and wear. Check brake pressure at the wheel cylinders and/or calipers. Brake System Diagnosis and Repair September, 2005 17