Liquid cooled pump motor unit

A pump motor assembly comprising a stator (1) with windings (3), said stator being imbedded in a plastic molding material (5) and surrounded by a stator casing (4), a rotor shaft (6) mounting a rotor (2) in a rotor chamber in said stator, a diffuser housing (9) arranged adjacent said stator and enclosing at least partly the stator windings, said stator casing (4) and diffuser housing (9) being an integral one-piece assembly, means defining a flow channel (10) in said diffuser housing for circulation of a cooling medium from an inlet (15) to an outlet (14) in said diffuser housing, a pump wheel (12) disposed in said flow channel mounted on said rotor shaft to effect circulation of the cooling medium through said flow channel (10) over the stator windings to cool the same, means defining openings (11) in said pump wheel allowing cooling medium to flow through the pump wheel and out from space (13) interiorly of the windings (3), said rotor shaft rotatably journalled in the casing on bearing means (8) and including a space (17.sup.a) around the rotor shaft (6) between the pump wheel and the bearing means and at least one drainage channel (17) arranged to extend from said space (17.sup.a) to exteriorly of the pump motor assembly.