Abstract: It is common in the operation of a construction machine to utilize several different functional modes. Some modes may predominately utilize the braking systems of the machine will other modes may predominately utilize the engine to operate the various implements. In either case, supplemental cooling of these systems is often desirable. The present invention provides a cooling system wherein each axle assembly has a cooling system in addition to the conventional cooling system for the engine. All the cooling systems communicate with a common heat exchanger. A pump is provided to circulate oil from the axle assemblies, as well as coolant from the engine through the heat exchanger to reduce the temperature of one of the fluids. A pair of sensors are engaged with the engine and the axles to selective actuate a clutch member to provide driving engagement between the engine and the pump in response to either component reaching a preselected temperature.