PLATFORM GP-OPERATOR 3988997 - Caterpillar

Illustration 1 g01260438
View of the underside of the cab on the left upper frame
(1) Cab brake manifold
(2) Service brake pressure switch
Illustration 2 g01260441
(2) Service brake pressure switch
(3) Automatic retarder control solenoid for the front brakes
(4) Inlet from the brakefoot pedal valve brake port
(5) Inlet from brake foot pedal valve tank port
(6) Automatic retarder control solenoid for the rear brakes
(7) Outlet to the brake foot pedal valve
(8) Outlet to the front brakes
Illustration 3 g01260463
(9) Outlet to hydraulic tank
(10) Outlet to rear brakes
(11) Pressure tap for service brake pressure
(12) Port for front brakes
(13) Port for rear brakes The cab brake manifold (1) is mounted under the cab on the left upper frame. This manifold contains the automatic retarder control (ARC) solenoid (3) for the rear brakes, and the brake solenoid (6) for the rear brakes.The ARC control solenoids (3) and (6) are part of the ARC system. The ARC system uses the rear service brakes and the front dry caliper brakes to automatically control the speed of the truck.The service brake pressure switch (2) sends a signal to the Brake ECM. The brake ECM uses the signal from the service brake pressure switch (2) to turn on the brake lights. In a low pressure situation, the Brake ECM will signal the monitoring system to activate the brake system check indicator.When the service brake pedal is pushed, pressurized oil flows from the service brake accumulators into port (13) on the brake valve. The oil flows directly out of port (7) to the brake foot pedal valve, through the double check valve, and into the slack adjuster. The oil is then directed to the rear brakes. When the brake pedal is released, the brake cylinder forces the fluid through the brakefoot pedal valve. This oil flows to port (5) of the brake valve, and out of port (9) back to the hydraulic tank. Brake oil also flows to the rear brakes when the Brake ECM commands the proportional control valve for the rear brakes for automatic retarding.When the brakes are applied or when automatic retarding is desired, the Brake ECM sends a signal to the control solenoid on the proportional control valve that is located within the brake valve. This allows pressurized oil to flow from the service brake accumulators into port (12) on the brake valve. Pressurized oil then flows from port (8) on the brake valve to the slack adjuster. The oil is then directed to the front brakes. When the Brake ECM no longer signals the control solenoid for the front brakes, oil is allowed to flow back through port (12) and out of port (9) back to the hydraulic tank.