A water pump is driven by a driving force generated by an internal combustion engine, and generates a larger driving force as a pressure introduced into a pressure chamber becomes higher. The pressure chamber is connected to a VSV through a first passage. A portion of an intake passage, which is located downstream of a throttle valve, is connected to the VSV through a second passage. An atmospheric pressure space is connected to the VSV through a third passage. In the VSV, the volume of wax in a temperature-sensitive case is increased to increase the ratio of the cross sectional area of an opening portion of the third passage, which is connected to the first passage, to the cross sectional area of an opening portion of the second passage, which is connected to the first passage, as the temperature of a coolant for the internal combustion engine increases.