Document 71vdXj7yZQRBwGQ0e0v846poV

BRAKE SYSTEM DIAGNOSIS AND TESTING LESSON ONE-MODULE 1 Pedal Eases Down Slowly A pedal that eases down slowly towards the floor, as firm even pressure is applied, indicates that the system is losing pressure. A pedal that eases down toward the floor may be caused by: Fluid leaking past the internal seals in the master cylinder. Pinhole leaks in the lines or hoses. Seepage from wheel cylinder or caliper seals. Air in the system. A leaking outlet/dump valve in the anti-lock brake system (ABS) electronic hydraulic control unit (EHCU). Pedal Eases Down Slowly Diagnosis To diagnose a pedal eases down slowly concern, perform the following tests: Check the fluid level in the master cylinder. Check for external leaks at the master cylinder. Check for external leaks in the hydraulic system. With the engine running at idle and the transmission in PARK, apply firm pressure to the brake pedal. - If the pedal eases down and there are no external leaks, check for: Air in the hydraulic system. An internal leak in the master cylinder. A leaking outlet/dump valve in the ABS EHCU. Perform the master cylinder bypass condition test. Bleed the brake system. Follow the Soft or Hard Brake Pedal Symptom Chart in the ABS Section of the workshop manual to diagnose a possible leaking outlet/dump valve in the ABS EHCU. Brake System Diagnosis and Repair September, 2005 13