CHASSIS AR 2278358 - Caterpillar

Illustration 1 g00659744
Hydraulic Schematic for the Fan Drive Circuit (early version) (1) Check valve (hydraulic oil cooler bypass). (2) Fan drive motor. (3) Hydraulic oil cooler. (4) Makeup valve.
Illustration 2 g00661282
Hydraulic Schematic for the Fan Drive Circuit (later version) (1) Check valve (hydraulic oil cooler bypass). (2) Fan drive motor. (3) Hydraulic oil cooler. (4) Makeup valve. (5) Radiator. (A) Line from fan drive pump. (B) Return line to hydraulic oil tank.
Illustration 3 g00291288
Location of Fan Drive Pump (gear or vane type pump)
Illustration 4 g00733404
Location of Fan Drive Pump (piston type pump)The fan drive pump is attached to the implement pump sections on the right rear side of the torque converter housing.Note: On newer machines, the fan drive pump is not mounted on the implement pump. The fan drive pump is located on the front housing of the engine on the right side of the machine.The fan drive circuit cools the hydraulic oil in the hydraulic oil tank. While the engine is running, the fan drive pump draws oil from the hydraulic oil tank. The oil then flows to fan drive motor (2). The oil pressure activates the fan drive motor and the fan rotates on the shaft. The fan draws air through hydraulic oil cooler (3) and the oil is cooled as the oil returns to the hydraulic oil tank.When the engine is first started and the hydraulic oil is cold, return oil from the fan drive motor cannot easily flow through the hydraulic oil cooler. The oil pressure overcomes check valve (1) and the check valve opens.Because of the resistance of oil flow through the hydraulic oil cooler, the oil flows through check valve (1) and back to the hydraulic oil tank. The bypass valve, which limits the maximum pressure in the hydraulic oil cooler, is set to open at 448 kPa (65 psi).When the oil temperature increases and the oil pressure decreases below 448 kPa (65 psi), the force of the spring in the check valve is greater than the force of the oil pressure. This allows the check valve to close. Now, the oil flows through hydraulic oil cooler (3) and back to the hydraulic oil tank.