SPEAKER 1U8677 - Caterpillar

Main Control Valve
The main control valve is situated in the hydraulic circuit between the hydraulic pumps and the implement cylinders, the travel motors, and the swing motor. The main hydraulic pump supplies high-pressure hydraulic oil to the main control valve. Pilot pressure oil from the main control valve is used by the ECM to command the movement of six primary valve spools in the main control valve. The six primary valve spools, in turn, control the flow of the high-pressure oil to the implement cylinders and motors. The main control valve determines the direction and speed of the implement cylinders and motors in proportion to the movement of the operator joysticks and travel lever/pedals. The six primary valve spools control the following components:
Stick cylinder (IN and OUT)
Swing motor (LEFT and RIGHT)
Left travel motor (FORWARD and REVERSE)
Right travel motor (FORWARD and REVERSE)
Boom cylinders (RAISE and LOWER)
Bucket cylinder (OPEN and CLOSE)Note: Refer to the appropriate sections in this manual for more information.