A regulatable coolant pump and a method for regulation of this regulatable coolant pump for internal combustion engines, which is driven by way of a pulley actives a valve slide using an electromagnetically activated piston pump equipped with a return spring in the form of a pressure spring. The pump implements a “pump feed” using many small “partial lifts.” A “leakage volume stream” that flows opposite to the “pumped volume stream” is superimposed on the “pumped volume stream” via the arrangement of circular apertures both in the inlet valve membrane of the working piston and in the outlet valve membrane so that the valve slide can be moved in defined manner and in a very robust and reliable manner, with low drive power via the defined superimposition of these two volume streams.