What Causes the Clicking Sound After Parking?

[BrooklynLee]

The cooling sounds from the catalytic converter, exhaust pipe, and turbocharger. Here are the detailed explanations: Cooling sound from the catalytic converter: The normal operating temperature of the catalytic converter ranges between 400-800 degrees Celsius. After turning off the engine, its operation gradually stops, and the temperature decreases, causing the internal metal components to expand and contract, resulting in the clicking sound. Cooling sound from the exhaust pipe: During cold idling, the exhaust pipe can reach temperatures above 200 degrees Celsius. Under high load or when unburned fuel mixture ignites in the exhaust pipe, the temperature can rise even higher. Thus, the exhaust pipe also expands and contracts, producing the clicking sound, often originating from the front end or flexible joint of the exhaust pipe. Turbocharger cooling sound: Under normal conditions, exhaust gases can reach temperatures of 600-700 degrees Celsius, accelerating the turbocharger's rapid rotation and friction-generated heat. After shutdown, the heat expansion and contraction become very noticeable, leading to the clicking sound.