Engine cooling system having coolant temperature sensor

An engine cooling system having a coolant temperature sensor, the engine cooling system comprising:

• a second coolant temperature sensor disposed to sense a second coolant temperature of a coolant discharged from an engine;
• a radiator radiating heat while a part of the coolant discharged from the engine is passed through the radiator;
• a coolant control valve unit disposed to control coolant passing through the radiator and coolant supplied from the engine;
• and
• a control unit configured to control the coolant control valve unit according to an operation condition and the second coolant temperature sensed by the second coolant temperature sensor,
• wherein the control unit calculates a first coolant temperature at a coolant entrance of the engine using the second coolant temperature and a heat rejection rate of the engine, the heat rejection rate being calculated according to the operation condition,
• wherein the control unit calculates a third coolant temperature of a coolant discharged from the radiator according to a heat radiation of the radiator, the heat radiation being calculated according to the operation condition, and
• wherein the control unit controls an opening degree of the coolant control valve unit using the first, second, and third coolant temperatures.