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1. Fault symptoms: ① The new hydraulic oil installed replaced deteriorated after being used for a short time； ②The temperature of the automatic transmission is too high, and smoke is coming out from the fuel filler port. 2. Causes of the failure: ① Blockage in the hydraulic oil radiator pipeline ； ②The free play of the clutch or brake is too large ； ③The pressure relief valve leading to the hydraulic oil radiator is stuck ； ④The oil pressure in the main oil circuit is too low, causing the clutch or brake to slip during operation ； ⑤Cars are used improperly, often under excessive load – for example, they are frequently used for towing, or driven at high speeds or in a reckless manner. 3. Fault diagnosis and troubleshooting: Drive the car at medium to low speeds; once the automatic transmission reaches its normal operating temperature, check the temperature of the hydraulic fluid radiator of the automatic transmission while the engine is running. Under normal conditions, the temperature of the hydraulic oil radiator can reach around 60°C. ⑴If the temperature of the hydraulic oil radiator is low, it indicates that the oil pipes are blocked, or the pressure-reducing valve leading to the hydraulic oil radiator is stuck. In this way, the hydraulic oil is cooled in a timely manner, preventing the oil temperature from rising too high and causing it to deteriorate. ⑵If the temperature of the hydraulic oil radiator is too high, it indicates that the free play of the clutch or brake is too large; in this case, the automatic transmission should be removed for adjustment. ⑶If the hydraulic oil temperature is normal, the oil pressure in the main circuit should be measured. If the oil pressure is too low, check the adjustment of the throttle cable or the throttle position sensor. If the throttle cable or throttle position sensor is installed properly, the automatic transmission should be removed to check whether the oil pump is excessively worn, whether there is any sticking in the pressure control valve in the main oil circuit and the throttle valve, and whether there are any leaks in the main oil circuit. ⑷If all the above checks show normal results, the fault may be caused by the vehicle being driven under excessive load frequently, or by the use of hydraulic oil of an inappropriate grade as required. To address this, all the hydraulic oil can be drained out and replaced with hydraulic oil of the specified grade and quantity