SPRING 1479929 - Caterpillar

Illustration 1 g00537839
Hydraulic oil cooler compartment (1) Supply line from the hydraulic cooling piston pump (2) Fan motor makeup valve (3) Return lineThe fan motor makeup valve (2) for the hydraulic cooling fan motor is mounted on the floor below the fans.
Illustration 2 g00537841
Front of engine radiator (1) Supply line from the radiator cooling piston pump (2) Fan motor makeup valve (3) Return lineThe fan motor makeup valve (2) for the radiator cooling fan motor is mounted on the fan support structure below the fan.
Illustration 3 g00932051
Fan motor makeup valve (4) Passage from cooling pump (5) Check valve (6) Return passageReturn oil from the fan motor is used as makeup oil. When the fan stops operating, the makeup oil is used to prevent a vacuum condition in the fan motor.When the cooling piston pump control valve signals the cooling piston pump to destroke, the supply of oil to the fan motor is reduced. The fan motor continues to rotate due to the mass of the fan blade assembly. Continued rotation of the fan motor creates a vacuum in passage (4) of fan motor makeup valve (2). This vacuum lowers the pressure in the passage (4). The combined force of the vacuum and the force of the spring is less than the force of the pressure that is in return passage (6). Check valve (5) will open.When check valve (5) is open, return oil flows to passage (6) from the cooling pump. The return oil enters the fan motor through line (1). This makeup oil circuit eliminates the possibility of cavitation in the fan motor.The same process occurs when the machine is shut down.