CYLINDER GP-BOOM 1251545 - Caterpillar

Illustration 1 g00915237
The parking brake control valve is located on the left side of the rear frame.
Illustration 2 g00900202
Parking brake control valve (1) Parking brake oil pressure switch for electronic transmission control (2) Port from pilot oil pressure reducing valve (3) Solenoid (4) Pressure tap for parking brake system (5) Port to hydraulic tank (6) Port to parking brakes (7) Port to brake release sequence valve (8) Parking brake oil pressure switch - remote control lightThe parking brake control valve has two solenoids (3) controlled by a parking brake switch in the operator station. The optional remote control system when fitted also controls the operation of solenoids (3).
Illustration 3 g00900210
Schematic for the parking brake control valve (1) Parking brake oil pressure switch for electronic transmission control (2) Port from pilot oil pressure reducing valve (3) Solenoid (4) Pressure tap for parking brake system (5) Port to hydraulic tank (6) Port to parking brakes (7) Port to brake release sequence valve (8) Parking brake oil pressure switch - remote control light (9) Valve spoolsWhen the engine is running and the parking brake switch is in the ON position, no power is supplied to solenoids (3). Oil pressure from the pilot oil pressure reducing valve at port (2) is stopped by valve spools (9). The parking brakes are engaged by the force of the parking brake springs. Oil from the parking brakes is free to return to the hydraulic tank through port (6), valve spools (9) and hydraulic tank port (5) .When the parking brake switch is moved to the OFF position, power is supplied to solenoids (3). Solenoids (3) energize and move valve spools (9). Oil pressure from the pilot oil pressure reducing valve at port (2) flows through valve spools (9) and port (6) to the parking brakes. Oil pressure disengages the parking brakes and allows the machine to move.Machines equipped with the optional brake release system contain a sequence valve which is connected to port (7) of the parking brake control valve. When the parking brake is disengaged, oil pressure is directed through port (7) to the brake release sequence valve.