| 摘要 |
PROBLEM TO BE SOLVED: To enable to judge thermostat failure more precisely irrespective of the extent of temperature rise of cooling water. SOLUTION: With this diagnosis device, anticipated temperatureθe-p of cooling water for engine 1 based on engine-operation parameter such as engine load, etc., is calculated. Actual temperatureθea of cooling water is detected with water temperature sensor S1. Radiation volume Q orh from radiator 3 is calculated based on the aggregate of values given from deviation ofθea deducted fromθep multiplied by car velocity Vs and current deviation value ofθea deducted fromθep. On the other hand, heat-intake volume Q ig of cooling water from engine 1 is calculated based on engine operation parameter such as engine load. Ratio of radiation Q orh to heat-intake volume Q ig is calculated as heat volume ratio R. If heat volume ratio R is greater than the judged thresholdα1 when anticipated temperatureθep reaches around specified valve-opening temperature of thermostat 5, it is judged that as valve-opening failure due to excessive radiation from radiator 3 leaving thermostat 5 open.
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