User manual BENDIX M-21-M-22 ANTILOCK MOD ASSY

[. . . ] Brake application air enters the supply port of the modulator and flows to, and through, the open exhaust solenoid then to the exhaust diaphragm. Air pressure, along with spring force, seats the exhaust diaphragm on the exhaust passage thus preventing the escape of service air. Simultaneously, application air flows to the supply diaphragm and forces it away from its seat. Air flows past the open supply and out the modulator delivery port to the service brake chambers. 2 EXHAUST DIAPHRAGM EXHAUST SOLENOID EXHAUST PORT BRAKE VALVE SUPPLY SOLENOID SPRING BRAKE CHAMBER SUPPLY DIAPHRAGM SPRING FIGURE 3 - M-21TM, M-22TM MODULATOR NON-ANTILOCK APPLICATION OF SERVICE BRAKES EXHAUST DIAPHRAGM EXHAUST SOLENOID EXHAUST PORT BRAKE VALVE SUPPLY SOLENOID SPRING BRAKE CHAMBER SUPPLY DIAPHRAGM SPRING FIGURE 4 - M-21TM, M-22TM MODULATOR NON-ANTILOCK APPLICATION HELD POSITION 3 EXHAUST DIAPHRAGM EXHAUST SOLENOID EXHAUST PORT BRAKE VALVE SUPPLY SOLENOID SPRING BRAKE CHAMBER SUPPLY DIAPHRAGM SPRING FIGURE 5 - M-21TM, M-22TM MODULATOR NON-ANTILOCK EXHAUST OF SERVICE BRAKES (NORMAL) NON-ANTILOCK EXHAUST The manner in which air exhausts through the modulator differs, depending upon how rapidly the brake application is released by the driver. [. . . ] De-energizing the exhaust solenoid opens its inlet and closes its exhaust. Opening the exhaust solenoid inlet, allows application air to flow to the control side of the exhaust diaphragm which then seals the exhaust passage. With the exhaust diaphragm seated, further exhaust of brake chamber air pressure is prevented. Because the supply solenoid remains energized the supply diaphragm remains seated, thus preventing application air from flowing to the delivery port and out to the brake chamber. The modulator can enter the antilock exhaust or re-apply mode from the antilock hold mode. 5 EXHAUST DIAPHRAGM EXHAUST SOLENOID EXHAUST PORT BRAKE VALVE SUPPLY SOLENOID SPRING BRAKE CHAMBER SUPPLY DIAPHRAGM SPRING FIGURE 7 - M-21TM, M-22TM MODULATOR ANTILOCK EXHAUST OF BRAKES ANTILOCK RE-APPLY If the antilock controller senses that wheel speed has increased sufficiently to require reapplication of braking pressure, it de-energizes the supply and exhaust solenoids. With both solenoids de-energized, the modulator re-applies air to the brakes in the same manner it did during a nonantilock application. 3. Test air line fittings for excessive leakage and tighten or replace as necessary. Perform the ROUTINE OPERATION AND LEAKAGE TESTING described in this manual. OPERATION & LEAKAGE TESTS LEAKAGE TESTING 1. Park the vehicle on a level surface and block or chock the wheels. Release the parking brakes and build the air system to full pressure. Turn the engine OFF and make 4 or 5 brake applications and note that the service brakes apply and release promptly. Build system pressure to governor cut-out and turn the engine OFF. Make and hold a full service brake application. Apply a soap solution to the exhaust port of the modulator. Leakage should not exceed a 1" bubble in less than 3 seconds. If leakage exceeds the specified maximum, replace the modulator. Apply a soap solution around the solenoid assembly (top and bottom). Leakage should not exceed a 1" bubble in less than 3 seconds. If leakage exceeds the specified maximum, tighten the solenoid cap screws and re-test. If the leakage remains excessive after re-testing, replace the modulator. PREVENTIVE MAINTENANCE GENERAL Perform the tests and inspections presented at the prescribed intervals. If the modulator fails to function as described, or leakage is excessive, it should be replaced with a new or genuine Bendix remanufactured unit, available at any authorized parts outlet. EVERY 3 MONTHS, 25, 000 MILES OR 900 OPERATING HOURS 1. Remove any accumulated contaminates and visually inspect the exterior for excessive corrosion and physical damage. [. . . ] Never exceed manufacturer's recommended pressures. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a component or plug unless you are certain all system pressure has been depleted. Use only genuine Bendix ® replacement parts, components and kits. [. . . ]