The pump (2) has a housing (5) made of a drum (10) with a base (11) and comprising an open end (12) at a side turned toward the base. A cover (14) with a hole (20) for passage of a rotor shaft (7) is used at an open side, which is turned away from the base. A bearing (22) is provided at outer circumference of the drum, and a belt pulley collar (26) is supported on the bearing. A coupling disk (30) is rotated and detached from the belt pulley collar and connected with the belt pulley collar in a torque proof manner. The coupling disk comprises an opening.
