A mechanical coolant pump for an internal combustion engine includes an impeller pump wheel. The pump housing comprises an outlet valve arrangement arranged between an outlet volute and a pump outlet, and a support portion. The pump housing closes and/or opens a valve opening. The outlet valve arrangement comprises a valve body which pivots. The valve body comprises a closing element which covers the valve opening, and first and second end disks. The closing element comprises an opening seat in a closed valve position. The first and second end disks are parallel to each other, are arranged at opposite axial ends of, and perpendicular to, the closing element, and rotate around a pivot axis. The first and second end disks each comprise a radial clamping nose which acts with the support portion to radially push the closing element against the opening seat in a closed valve position.