There is air leakage in the engine compartment after the car is turned off. What's the matter?

The reason why there is air leakage sound in the engine compartment after the car is turned off is that the air flow of the exhaust pipe three-way catalyst is cold and normal.

Cooling sound of three-way catalytic converter: The normal working temperature of three-way catalytic converter is 400-800℃. After the flameout, its work will slowly stop, the temperature will drop, the metal parts inside will expand with heat and contract with cold, and then make an abnormal noise. Exhaust pipe cooling sound: when the general cold car is idling, the exhaust pipe temperature can reach above 200.

When the vehicle is under high load or the mixture in the exhaust pipe is burning, the temperature will be higher, so the exhaust pipe will also expand with heat and contract with cold to make abnormal noise, which often comes from the front end and soft joint of the exhaust pipe.

Extended data:

The sound of air leakage in the engine compartment after the automobile flameout is introduced as follows:

The normal working temperature of the engine is basically maintained at about 90℃. When the engine is stopped and turned off, the temperature of the engine will not drop immediately. With the accumulation of engine waste heat, it is easy to damage the plastic parts and wiring harness in the engine compartment, and even lead to spontaneous combustion of the vehicle.

At this time, it is necessary for the cooling fan to continue to work after the vehicle is stopped and turned off (in general, the cooling fan directly takes electricity from the battery, so the power failure will not affect its work) to cool the engine. When the engine temperature drops to a certain value, the cooling fan will automatically stop working.

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