Water pump and method for producing water pump

A water pump comprising:

• a pump housing having a cylindrical portion at an axial end;
• a drive shaft rotatably supported in the pump housing;
• a pulley including a discal end wall that is connected to an end portion of the drive shaft and a cylindrical base part that is integrally connected to an outer periphery of the discal end wall and shaped to surround the cylindrical portion;
• a bearing that is interposed between the cylindrical base part and the cylindrical portion to rotatably bear the drive shaft;
• and
• an impeller that is connected to the other end of the drive shaft to rotate integrally, wherein
• the discal end wall is formed with a plurality of through openings that communicate an inside with an outside of the discal end wall,
• relative to a rotational axis of the water pump, each of the through openings defines, at a location on each through opening that is most radially distant from the rotational axis of the water pump, a pathway groove that extends substantially along an inner cylindrical surface of the cylindrical base part,
• an opening area of the pathway groove is smaller than that of the corresponding through opening,
• a width of the pathway groove is reduced as the pathway groove extends radially outward, and
• the pathway groove extends through the discal endwall along a direction that is parallel to a longitudinal axis of the drive shaft.