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Why Does the Engine Make Noise After the Car is Turned Off?

1 Answers

LeStephanie

07/24/25 7:56am

Here are the reasons why the engine makes noise after the car is turned off: 1. Cooling sound of the catalytic converter: The normal operating temperature of the catalytic converter is 400-800°C. After the car is turned off, its operation gradually stops, and the temperature drops, causing the internal metal components to expand and contract due to heat, resulting in abnormal noise. 2. Cooling sound of the turbocharger: Normally, the exhaust gas temperature reaches 600-700°C, which accelerates the rapid rotation of the turbocharger and generates friction heat. After the car is turned off, the heat expansion and contraction are also very noticeable, leading to abnormal noise. 3. Uneven cooling of the engine: After driving for a while, the engine temperature is very high. After the car is turned off, the temperature of various components drops, and the heat expansion and contraction cannot be completely uniform, which inevitably causes friction between the internal metal components due to cooling contraction, resulting in abnormal noise. 4. The cooling fan is running: There is no need to worry as it will automatically turn off after the water temperature drops. If the cooling fan is working, it means the engine temperature is still too high, and the fan will continue to operate for one to two minutes.

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