BENDIX TCH-020-007 User's Manual
Contents
1. Technical Bulletin Bulletin No PRO 20 07 Effective Date 1 1 91 Cancels N A Page 1 of 3 Subject Ford F Series Truck Hydraulic Parking System HR 1 Hydraulic Relay Noise SUPPLY RESERVOIR CONTROL DELIVERY DELIVERY EXHAUST PORT BACK HR 1 HYDRAULIC RELAY VALVE While some noise is inherent in the operation of a hydraulic brake system pump check valves and pressure regulating valves opening and closing operators occasionally report hearing excessive noise emanating from the HR 1 hydraulic relay valve The HR 1 is used on Ford truck model series 600 700 800 900 7000 and 8000 Described variously as a buzzing humming popping or groaning sound the excessive noise is often attributed to a faulty HR 1 Because the HR 1 is mounted on the firewall adjacent to the Hydro Max booster sounds are amplified Excessive HR 1 noise can be the result of air in the parking brake system PARKING BRAKE CONTROL VALVE TW 41 PARKING BRAKE PARKING BRAKE CHAMBER CHAMBER SAGINAW PUMP BRAKE HYDRO MAX BOOSTER 1 CHAMBER 4 PARKING BRAKE BRAKE DRUM PARKING BRAKE CHAMBER TYPICAL HR 1 SYSTEM In order to eliminate the excessive HR 1 noise it is necessary to bleed the air from the spring brake actuators using the vehicle manufacturers recommended procedure Ifthe HR 1 noise is only temporarily eliminated and reappears ina short period of time then it is likely that an external leak exists somewhere in the2. Hydro Max and or parking brake system which allows air to reenter the system Check for fluid leakage and repair or replace as necessary WEDGE TUBE BRAKE BACKING ABUTMENT HYDRAULIC SPRING BRAKE PLATE TAPPET PARKING ACTUATOR WITH LUCAS GIRLING EXPANDER Most fluid leaks can be found by visual inspection however the spring brake actuators can LEAK INTERNALLY INTO THE EXPANDER unit ofthe Lucas Girling A2LS drum brake Internal hydraulic spring brake leakage can not be detected visually unless the actuator is removed from the expander and checked for wetness inside the wedge tube CAUTION Thoroughly read the vehicle manufacturer s maintenance manual before attempting removal of the hydrau lic spring brake actuators A VERY HIGH SPRING LOAD IS USED AND INJURY CAN RESULT FROM IMPROPER HANDLING input Tappet Piston MANUAL ADJUSTOR BACKING ADJUSTER PLATE k Y HERE WHEEL EXPANDER Sea Position SAEED DIGDDEE rap ee i CYLINDER gt C X N PARKING WHEEL CYLINDER 3 4 TAPERED LINING AND SHOE ASSEMBLY Roller Tappet LINING Piston INSPECTION a HOLE SPRINGS TYPICAL LUCAS GIRLING A2LS BRAKE ASSY LUCAS GIRLING EXPANDER Both actuators should be checked for internal leakage If evidence of internal leakage is found in either of the actuators it may be necessary to repair or replace all components containing BRAKE FLUID SEALS that may have been exposed to hydraulic fluid from the leaking spring brake
3. actuator The affected components are the A2LS expander unit A2LS wheel cylinder and possibly the master cylinder Drain flush and replace the brake fluid in the service brake system to eliminate any hydraulic fluid contamination
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