TUBE A. 5J3650 - Caterpillar

Main control valve (3) is located in the hydraulic system between the pumps and actuators (cylinders and motors). Depending on the machine operation, components and passages in the valve control oil flow and pressure in the circuits from the pumps to actuators.The main control valve consists of right body (44) and left body (45). The main control valve is coupled together with bolts to make one assembly. The following control valves are in parallel in right body (44).
Right travel control valve (15).
Attachment control valve (17).
Bucket control valve (18).
Boom I control valve (19).
Stick II control valve (37).The following control valves are in parallel in left body (45).
Straight travel control valve (14).
Left travel control valve (13).
Swing control valve (12).
Stick I control valve (10).
Boom II control valve (8).The left body has inlet ports (30) and (31) and return port (23). The drive pump oil flows into inlet port (31). The idler pump oil flows into inlet port (30). The oil flow of the drive pump and the oil flow of the idler pump is controlled by the main control valve. The oil flow is supplied to cylinders and/or motors that are selected for operation. Return oil from cylinders and/or motors enters the main control valve. The oil then flows out of return port (23) and back to hydraulic tank (39) through return line.Right Body (44)
Line relief valves (33) and (34) limit the circuit pressure.
When the control levers are in the NEUTRAL position or when the control levers are moved partially, relief valve (22) and negative flow control orifice (21) destroke the main pump.
When the control levers are in the NEUTRAL position, boom drift reduction valve (7) prevents boom cylinder drift.
Pressure switch (4) generates electric signals for the Automatic Engine Speed Control. Travel pressure switch (5) generates electric signals for the Automatic Engine Speed Control.
Load check valve (16).Left Body (45)
Stick cylinder relief valves (26) and (2).
Relief valve (25) and negative flow control orifice (24).
Stick drift reduction valve (1) prevents stick cylinder drift when the main control valves are in the NEUTRAL position.
Main relief valve (29) limits the main hydraulic system pressure.
Load check valve (11).The following five configurations are the functions of the main control valves.
When the main control valves are in the NEUTRAL position, no pump oil flows to the cylinders and the motors.
Individual valve operation
The main control valve controls the negative flow control signal when the control levers are in the NEUTRAL position or when the control levers are moved partially.
Prevention of cylinder drift with the load check valve.
Limit the circuit pressure with the relief valve operation.The description of some components that are installed on the main control valve or in the main control valves will be listed separately. Refer to the appropriate sections that are in this module for further information on the components.
For more information on pressure switch (4) and travel pressure switch (5), refer to Systems Operation, "Gear Pump (Pilot)".
For more information on boom drift reduction valve (7), refer to Systems Operation, "Boom Hydraulic System".
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