Why does the engine buzz after turning off?

[McPiper]

It is normal for the engine to make noise after turning off the vehicle. More details about the noise after turning off the engine are as follows: 1. The noise is not from the engine itself but from the cooling fan. 2. The normal operating temperature of the engine is maintained at around 90°C. After parking and turning off the engine, the temperature does not drop immediately. The accumulation of residual heat can easily damage plastic components and wiring harnesses in the engine compartment, and in severe cases, may even cause the vehicle to catch fire. 3. The cooling fan continues to operate after the vehicle is turned off (generally, the cooling fan draws power directly from the battery, so turning off the engine does not affect its operation) to cool the engine. Once the engine temperature drops to a certain level, the cooling fan will automatically stop working.