A mechanical coolant pump for an internal combustion engine includes a main pump body configured to be stationary. A pump wheel is rotatably supported by the main pump body. The pump wheel comprises a central axial inlet opening. The pump wheel is configured to pump a coolant from the central axial inlet opening radially outwardly. A valve disk configured to be axially shiftable is arranged in the pump wheel. An actuator is configured to actuate the valve disk so as to close the central axial inlet opening in a closed position of the valve disk.