A coolant pump includes an impeller pump wheel, a pump housing defining an outlet volute, and an outlet valve arrangement. The pump housing comprises an outlet volute housing which defines a first outlet channel comprising a valve opening. The valve opening is defined by a valve seat which defines a valve seat plane and a symmetry plane. The symmetry plane is arranged in the middle of and rectangular to the valve seat plane. The outlet valve arrangement is in the first outlet channel and comprises a valve flap which opens/closes the valve opening. The valve flap comprises a flap seat corresponding to the valve seat. The valve flap rotates around a pivot axis parallel to the symmetry plane and having an eccentricity from the symmetry plane which is between 1/20 and 1/1 of a distance of the pivot axis to the valve seat plane when the valve flap is open.