Abstract: A switchable mechanical motor vehicle coolant pump includes a rotatable drive shaft, a drive wheel, a coolant pump wheel comprising a radially outer outlet, a control slider, and an actuation system which hydraulically actuates the control slider. The drive wheel and the coolant pump wheel are each connected to the drive shaft. The control slider shifts axially with respect to the coolant pump wheel to at least partially close the radially outer outlet. The actuation system includes pressure chamber(s), an auxiliary pump having an auxiliary pump wheel provided integrally with the coolant pump wheel, and a switchable control valve which controls a pressure level within the pressure chamber(s). The auxiliary pump wheel provides a hydraulic actuation pressure for the pressure chamber(s) and comprises a ring-shaped pumping channel in which pumping vanes are arranged equidistantly along a circumference of the ring-shaped pumping channel so as to define equal pumping chambers therebetween.