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| Illustration 1 | g01420303 |
Fan Hydraulic System (Operating) (1) Pump assembly (2) Fan pump (3) Steering pump (4) Relief valve (5) Fan motor assembly (6) Fan motor (7) Rear charge filter assembly (8) Suction strainer (9) Tank | |
The fan pump is driven by the engine. The fan pump draws oil from the hydraulic tank through a suction strainer. The fan motor is connected to the cooling fan. The fan pump directs oil flow to the inlet of the fan motor.
Inside the fan motor, supply oil seats the anticavitation check valve and supply oil acts on the differential pressure valve. As pump supply pressure increases, the fan motor begins to rotate. Oil that exits the outlet side of the fan motor acts against the differential pressure valve. This oil acts in conjunction with the spring and against the supply pressure. The differential pressure valve maintains the pressure drop across the fan motor in order to control fan speed.
When the engine is stopped, the inertia of the fan blades and of the rotating components in the fan motor cause the fan motor to continue to turn for a brief period. Since the engine is not operating during this time, the fan pump does not provide flow in order to prevent cavitation of the motor. In this case, the anticavitation check valve opens. The anticavitation check valve prevents the motor from cavitating by allowing the fan motor to draw oil from the return line.
The case drain line for the fan motor dumps oil from the motor case directly into the hydraulic tank.
Supply oil from the fan motor is directed to the rear charge filter. The rear charge filter directs charge oil to the axle propulsion system.