BEARING 5313531 - Caterpillar

Hydraulic Fan 834K
Illustration 1 g03383912
(1) Piston pump (Hydraulic fan)
(2) Engine cooling fan solenoid
(3) Hydraulic oil filter
(4) Hydraulic oil cooler
(5) Hydraulic fan piston motor
(6) Case drain oil filter Hydraulic fan pump (1) is a variable displacement piston pump. In the hydraulic fan system, the demand for more fan speed through an increase of oil flow is supplied by the hydraulic fan pump (1). The discharge pressure of the hydraulic fan pump (1) is controlled by solenoid valve (2) (Hydraulic fan). When solenoid valve (2) receives a change in current from the engine electronic control module (ECM), signal pressure to the fan pump (1) will change accordingly. As signal pressure changes, the displacement will change in order to maintain the pump pressure above the signal pressure. The engine ECM receives information from temperature sensors for the engine coolant and hydraulic oil.When the current to solenoid valve (2) is at the maximum, the fan pump is at minimum output. If the fan speed solenoid fails or there is another problem in the electrical circuit for the hydraulic fan system, the fan pump will advance to high-pressure cutoff. Then, the pump will produce maximum output. The maximum output that is provided by fan pump (1) is controlled by the adjustment of the high-pressure cutoff spool in the pump control valve.The fan motor is a reversible fixed displacement motor that is equipped with a makeup valve. The makeup valve allows the hydraulic oil to flow from the fan motor outlet through the makeup valve back to the fan motor inlet. This flow will prevent cavitation in the motor during deceleration.When the engine is first started and the hydraulic oil is cold, the oil from the piston motor cannot easily flow through the hydraulic oil cooler. Oil pressure will increase in the hydraulic oil cooler. The check valve for the hydraulic oil cooler bypass will open. The check valve limits the maximum oil pressure drop through the oil cooler. As the hydraulic oil temperature increases, the pressure drop of the oil through the oil cooler will decrease. The force of the spring in the check valve (hydraulic oil cooler bypass) is greater than the force of the oil pressure. Then, the check valve will close. The hydraulic oil will flow through the oil cooler (4) into the hydraulic tank.When the engine is started and if all temperatures for the sensors are below the key target temperatures the engine ECM will send the maximum current to solenoid valve (2). Signal oil to the flow control spool is open to the hydraulic tank through the solenoid valve (2). Supply oil is directed to the actuator piston in order to destroke the pump (1). The angle of the pump swashplate is at a minimum. The pump (1) will produce a minimum flow.As one of the temperatures of the three sensors increases above the key target temperature, the engine ECM sends a proportional reduction in current to solenoid valve (2). Solenoid valve (2) will start to shift. This action