118 Maintenance Check Valves Follow the procedure below to check out the air tank check valves at least once a year. This is to see if air pressure is maintained in the tanks when the air pressure is depleted in the supply tank (wet tank). DANGER Before working on or inspecting the vehicle, set the parking brakes, place the transmission in neutral and block the wheels. Failure to do so can result in unexpected vehicle movement and can cause serious personal injury or death. Note: The check valves should be checked at least once per year. 1 Chock the rear wheels. 2 Let the compressor build up air pressure to the governor cut-off. 3 Bleed the air pressure from the supply tank (wet tank).
4 Check the air pressure gauges on the instrument panel to see if the pressure is maintained in both primary and secondary air tanks. 5 Any bleed-off from one or both of the tanks indicates a defective check valve; replace valve. 6 Repressurize the system and remove the wheel chocks. DANGER Compressed air components can separate violently during disassembly if air pressure is present. Before servicing any part of the brake air system, completely release the air pressure. Failure to do so can result in serious personal injury or death. WARNING To prevent personal injury, always drain the air supply from the vehicle before attempting to repair or replace a component.
Wear eye protection and take care not to get fingers caught in the slack adjusters when spring brakes are applied. WARNING Always wear appropriate eye protection to prevent the risk of injury due to contact with engine debris or fluids.