Failure detection apparatus for cooling system of internal combustion engine

A failure detection apparatus for a cooling system of an internal combustion engine, said cooling system having a radiator, a cooling water pipe for circulating a cooling water in said engine to said radiator, and a thermostat provided in said cooling water pipe for opening and closing said cooling water pipe, said failure detection apparatus detecting failure of said thermostat and comprising:

• a vehicle speed sensor for detecting a vehicle speed of a vehicle driven by said engine;
• one or more operating condition sensor for detecting an operating condition of said engine, said one or more operating condition sensor including cooling water temperature sensor for detecting a temperature of the cooling water;
• an estimated cooling water temperature calculating module for calculating an estimated cooling water temperature of said engine according to said operating condition detected by said one or more operating condition sensor;
• and
• a determining module for comparing said estimated cooling water temperature and a determination threshold set according to said vehicle speed at the time said cooling water temperature detected by said cooling water temperature sensor has exceeded a predetermined water temperature, to thereby determine that said thermostat is normal.

A failure detection method for a cooling system of an internal combustion engine, said cooling system having a radiator, a cooling water pipe for circulating a cooling water in said engine to said radiator, and a thermostat provided in said cooling water pipe for opening and closing said cooling water pipe, said failure detection method detecting failure of said thermostat and comprising the steps of:

• a) detecting a vehicle speed of a vehicle driven by said engine;
• b) detecting an operating condition of said engine, said operating condition including a temperature of the cooling water;
• c) calculating an estimated cooling water temperature of said engine according to the detected operating condition;
• and
• d) comparing the estimated cooling water temperature and a determination threshold set according to the vehicle speed at the time the detected cooling water temperature has exceeded a predetermined water temperature, to thereby determine that said thermostat is normal.