A motor pump unit comprises an electric motor and a reversible internal gear machine. The latter has a multi-part housing in which an externally toothed pinion and an internally toothed hollow gear are arranged. A free space, in which a multi-part filler element is arranged, is configured between the gears. The filler element comprises radially movable sealing segments, between which a radial gap is configured. An axially movable sealing plate is arranged between axial faces of the gears and a housing part. This has a sealing plate control groove that is open to the faces of the gears and that can be pressurized, and which is open to the radial gap and located directly opposite thereto. The pinion segment and/or hollow gear segment has a radial sealing segment control channel that can be pressurized and extends transversely, is open to the radial gap, and ends directly in the radial gap.

A cooling pump assembly has a cooling pump, a mount, a shaft, and a driving set. Wherein, a driving unit of the driving set is configured to connect a device to be cooled and has a central hole fluidly communicating with an interior of the cooling pump. The shaft is inserted in the cooling pump, the mount, and the driving unit. The shaft is connected to the driving unit and the cooling pump. The shaft has a channel fluidly communicating with the device to be cooled and fluidly communicating with the channel and the central hole via multiple guiding holes of the shaft. Therefore, the cooling pump assembly and the device to be cooled can be driven by a same motor.