A thermostat trouble diagnosis system in an engine colling system

摘要

The invention relates to an apparatus for diagnosing thermostat trouble in an engine cooling system comprising a thermostat which works to open 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, or to close the valve to make the cooling water bypass a radiator when this temperature becomes less than the predetermined temperature. The apparatus comprises means for calculating a radiation heat amount from a radiator received by the cooling water for the engine and means for determining whether the thermostat trouble has occurred based on the radiation heat amount calculated by the means for calculating the radiation heat amount.