What Causes the Engine to Continue Making Noise After Shutting Off the Car?

[KiaraRose]

Engine noise after shutdown can be attributed to the catalytic converter, uneven engine cooling, or the cooling sound of the turbocharger. The specific reasons are explained below: Cooling sound of the catalytic converter: The normal operating temperature of the catalytic converter ranges from 400 to 800 degrees Celsius. After shutdown, its operation gradually stops, and the temperature decreases, causing thermal expansion and contraction of its internal metal components, which then produces abnormal noises. Turbocharger cooling sound: Under normal conditions, the exhaust gas temperature reaches 600-700 degrees Celsius, accelerating the rapid rotation of the turbocharger and generating friction heat. After shutdown, thermal expansion and contraction become very noticeable, resulting in abnormal noises. Uneven engine cooling: After driving for a period, the engine temperature becomes very high. Upon shutdown, the temperature of various components decreases, and thermal expansion and contraction cannot occur uniformly. This inevitably leads to friction between the internal metal components of the engine due to cooling contraction, causing abnormal noises.