A cooling system for a work vehicle includes a fan rotating in a first direction to generate an air flow in a first direction, a speed sensor sensing a speed of the fan, one or more sensors sensing a load of a power source, a temperature sensor sensing an ambient temperature, and a controller configured to determine the load of the power source, determine the speed of the fan, determine an estimated speed of the fan based in part on the load of the power source and the ambient temperature, determine a speed difference of the speed of the fan and the estimated speed of the fan, and determine changing the air flow to a second direction based in part on the speed difference and the load of the power source.

A fan drive device for use with a hydraulic pump featuring a constant displacement volume is disclosed. The fan drive device includes a hydraulic motor configured to be directly coupled to a fan. The hydraulic motor includes a first working connection, a second working connection, and a constant displacement volume. The fan drive device further includes a hydraulic valve having a pump connection and a tank connection. The hydraulic valve includes two fluid connections, each of which can be fluidically connected to the hydraulic motor. The hydraulic valve is designed as a proportional valve including a continuously adjustable control piston proportional to a control current of the hydraulic valve as the sole control mechanism for controlling the fan speed.

To provide a construction machine capable of reducing the time and labor of an operator and reliably preventing deterioration of cooling efficiency of a heat exchanger unit. A construction machine includes a heat exchanger unit having a plurality of heat exchangers, a cooling fan configured to supply cooling air to the heat exchanger unit during a forward rotation thereof, a controller configured to control an operation of the cooling fan, a timer configured to count an operation time period of forward rotation of the cooling fan, and a reverse rotation signal output switch configured to output to the controller a reverse rotation signal for causing the cooling fan to rotate in the reverse direction in response to an applied manual operation. The controller causes the cooling fan to rotate in the reverse direction for a second predetermined time period and resets the timer at the time of finishing the reverse rotation of the cooling fan, if the operation time period of forward rotation counted by the timer reaches a first predetermined time period, and controller causes the cooling fan to rotate in the reverse direction for the second predetermined time period when the reverse rotation signal is output from the reverse rotation signal output switch, and resets the timer at the time of finishing the reverse rotation of the cooling fan, even if the operation time period of forward rotation counted by the timer has not reached the first predetermined time period.