A warm-up device is provided in a cooling-water circuit, through which cooling water is circulated so as to pass through an engine. The warm-up device has a heat accumulating passage, in which a heat accumulating device is provided, and an accumulating-device bypassing passage bypassing the heat accumulating device. A waste-heat collecting device is provided in the cooling-water circuit so that heat is collected from exhaust gas from the engine and such collected heat is accumulated in the heat accumulating device. The cooling water is circulated through the heat accumulating device during a start-up operation of the engine in order to heat the cooling water flowing into the engine so as to quickly warm up the engine.

A cooling water control apparatus is a cooling water control apparatus for controlling a cooling apparatus having a first pipe which circulates cooling water through an engine; a second pipe which circulates the cooling water not through the engine; and a switching valve whose state is changed between opened and closed states, and has: a detecting device which detects first temperature of the cooling water in a pipe portion of the first pipe between the engine and the switching valve; and a determining device which determines that there is failure of the switching valve whose state is the closed state, if required period from the output of the command for changing the state of the switching valve from the opened state to the closed state until the first temperature reaches predetermined temperature is larger than predetermined target period.

A cooling water control apparatus controls a cooling apparatus having first pipe which circulates cooling water through an engine; second pipe which circulates cooling water not through the engine; a switching valve whose state is changed between opened and closed states; and a supplying mechanism which supplies cooling water, and has a determining device which determines whether there is failure of the switching valve based on difference between first temperature of cooling water in first pipe and second temperature of cooling water in second pipe after the command for changing the state of the switching valve from closed state to opened state is outputted; and a controlling device which controls the supplying mechanism to supply cooling water even after the engine stops, when the engine stops while the determining device determines whether there is failure of the switching valve.

A coolant control system of a vehicle includes an adjusting module that: (i) receives an engine output coolant temperature measured at a coolant output of an internal combustion engine; (ii) adjusts the engine output coolant temperature based on a reference temperature to produce a first adjusted coolant temperature; (iii) receives an engine input coolant temperature measured at a coolant input of the internal combustion engine; and (iv) adjusts the engine input coolant temperature based on the reference temperature to produce a second adjusted coolant temperature. The coolant control system also includes a difference module that determines a difference between the first and second adjusted coolant temperatures. The coolant control system also includes a pump control module that controls a coolant output of a coolant pump based on the difference between the first and second adjusted coolant temperatures.

A control unit stores a correlation between a temperature difference T between an inlet temperature and an outlet temperature of a heat exchanger for cooling of cooling water, and the amount of thermal deformation occurring in the heat exchanger. At the time when the cooling water is supplied to the heat-exchanging flow path having the heat exchanger, the control unit refers to the temperature difference T and the correlation to obtain the volume of flow of the cooling water supplied to the heat-exchanging flow path so that the amount of thermal deformation is less than or equal to a threshold amount of thermal deformation set in advance.