Water pump in vehicle

A water pump in a vehicle comprising:

• a pump cover which forms an upper side exterior appearance of the pump for housing an impeller to be rotated;
• a hollow rotor coupled on the same axis with the impeller to rotate altogether;
• a housing coupled to the pump cover to house the rotor and a stator therein;
• and
• a driving unit mounted to an underside of the housing for controlling the stator,
• wherein the pump cover includes a first rotation shaft extended toward the hollow in the rotor passed through the impeller,
• the housing includes a second rotation shaft extended toward the hollow in the rotor,
• the first rotation shaft has a communication hole formed therein to be in communication with the hollow, and
• the rotor has at least one communication passage recessed from an inner surface of a lower end portion of the hollow rotor in a radial direction.