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4. Check parking brake operation. Verify free movement and full release of cables and pedal. Also note if vehicle was being operated with parking brake partially applied. 5. Check brake pedal operation. Verify that pedal does not bind and has adequate free play. If pedal lacks free play, check pedal and power booster for being loose or for bind condition. Do not road test until condition is corrected. 6. Check booster vacuum check valve and hose. 7. If components checked appear OK, road test the vehicle. ROAD TESTING 1. If complaint involved low brake pedal, pump pedal and note if it comes back up to normal height. 2. Check brake pedal response with transmission in Neutral and engine running. Pedal should remain firm under constant foot pressure. 3. During road test, make normal and firm brake stops in 10 mph range. Note faulty brake operation such as low pedal, hard pedal, fade, pedal pulsation, pull, grab, drag, noise, etc. 4. Attempt to stop the vehicle with the parking brake only and note grab, drag, noise, etc. PEDAL FALLS AWAY A brake pedal that falls away under steady foot pressure is generally the result of a system leak. The leak point Internal leakage (seal by-pass) in the master cylinder caused by worn or damaged piston cups, may also be the An internal leak in the ABS system may also be the problem with no physical evidence. LOW PEDAL If a low pedal is experienced, pump the pedal several times. If the pedal comes back up worn linings, rotors, drums, SPONGY PEDAL A spongy pedal is most often caused by air in the system. However, thin brake drums or substandard brake lines HARD PEDAL OR HIGH PEDAL EFFORT A hard pedal or high pedal effort may be due to lining that is water soaked, contaminated, glazed, or badly worn. PEDAL PULSATION Pedal pulsation is caused by components that are loose, or beyond tolerance limits. The primary cause of pulsation are disc brake rotors with excessive lateral runout or thickness variation, or out of NOTE: Some pedal pulsation may be felt during ABS activation. BRAKE DRAG Brake drag occurs when the lining is in constant contact with the rotor or drum. Drag can occur at one wheel, all Drag is a product of incomplete brake shoe release. Drag can be minor or severe enough to overheat the linings, Minor drag will usually cause slight surface charring of the lining. It can also generate hard spots in rotors and HB BRAKES - BASE 5 - 3 |