BMW engine temperature is too high

    BMW Mini (MINI) sedan, the cumulative traveling 20,000 km, the engine temperature is too high, sustained high-speed electronic fan running phenomenon in motion.

    It reflects the owner, the ktag car appeared yesterday afternoon indicating high coolant temperature phenomenon, the next day will be just a few minutes after starting the engine with the engine coolant temperature gauge will display the engine temperature is too high, and then touch the radiator the upper and lower tube, the feeling is slightly hot, but did not feel the engine reaches normal operating temperature. After the car for repair, first with GT1 fault detector test, the engine electronic control unit (DME) is no fault code stored, read data stream found that the temperature of the engine coolant is 81 ℃ (car radiator fluid outlet does not coolant temperature sensor, it is impossible to determine the work through the thermostat temperature difference); because the fan is in high speed electronic state, read the refrigerant pressure within the air-conditioning control unit for 0.6 MPa, normal. According maintenance experience, after a long HK201 J2534 VCI period of operation of the engine coolant temperature indicator is too high, but on the radiator, liquid pipe temperature is very low, usually caused by faulty coolant pump, then did not give much thought to the cooling temperature and coolant temperature indicator gauge indicates the temperature difference between the fluid temperature sensor indicates, it is removed to check the coolant pump, coolant pump impeller found no skid marks or broken.

    So what is the cause of the engine temperature indication is too high, sustained high-speed electronic fan running it? By analyzing the vehicle cooling system control components, under normal pressure of the air conditioning system, the DME engine rely on two-wire negative temperature coefficient of coolant a temperature sensor to sense the temperature of the engine, only when the coolant temperature sensor fails, only the Transponder Chip actual temperature of the engine may cause a low, but the meter indicates engine temperature phenomenon. Remove the rear cylinder head coolant temperature sensor to measure its resistance to 510n. Because they do not know the standard range of the sensor, desperation can only replace the coolant temperature sensor, and then test found that the above symptoms disappeared.

    Analysts believe that the real reason for the above phenomenon is due to the coolant temperature sensor failure, causing coolant temperature signal response is too slow, making the engine warm-up time exceeds the maximum limit specified, then the engine entered CN900 Key Programmer the pre-set emergency operation mode, so that the actual engine temperature has not increased. In the actual troubleshooting process, ignoring the difference between the temperature of the coolant temperature coolant temperature sensor and instrument display indication of the details, take a lot of detours lead.