Patent ID: 6321696
Filing Date: 2001-11-27
Classification: F01P

Abstract:
An apparatus for diagnosing a thermostat trouble in an engine cooling system comprising a thermostat which opens a valve to make a cooling water flow through a radiator when the cooling water temperature for an engine becomes more than a predetermined temperature, and closes the valve to make the cooling water bypass the radiator when the temperature becomes less than the predetermined temperature, the apparatus comprising:calculating means for calculating a radiation heat amount from a radiator based on a predicted cooling water temperature calculated by using operating parameters indicating a condition of the engine operation and an actual cooling water temperature detected by a detecting means for detecting a temperature, and based on an integrating value of deviation between the predicted temperature and the actual temperature and a deviation between a present predicted temperature and the actual temperature; anddetermining means for determining whether the thermostat trouble has occurred, based on a result of the comparison between the actual or predicted temperature and a predetermined temperature, and the radiation heat amount calculated by the calculating means.