| 摘要 |
PROBLEM TO BE SOLVED: To provide a failure diagnostic device for an engine cooling system capable of diagnosing a failure of a valve gear in the engine cooling system directly and improving precision in diagnosis. SOLUTION: This failure diagnostic device for the engine cooling system provided with the valve gear 13 for detecting temperature of the cooling water flowing in a radiator 11 and controlling flow of the cooling water is provided with a temperature inferring means (step S60) for inferring temperature of the cooling water in an engine 20 based on a calorific value of the engine 20, quantity of heat radiation of a cylinder block 21 in the engine 20, quantity of heat radiation of the radiator 11, and quantity of heat radiation of a heater 15 used to heat the inside of a vehicle, an actual temperature detection means 23 for detecting actual temperature of the cooling water in the engine 20, and a failure determining means (steps S71-S75) for determining that the valve gear 13 causes a failure if the detected actual temperature is lower than the reference temperature set based on the temperature of the cooling water when the valve gear causes the failure in its opening in a scope of temperature of the cooling water rising while the valve gear is closed after the inferred temperature of the cooling water exceeds the reference temperature. COPYRIGHT: (C)2008,JPO&INPIT
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