What Causes Abnormal Noises from the Chassis After Parking?

[DelMargaret]

There are many reasons for abnormal noises from the chassis after parking a car. Below is a detailed analysis of the specific causes of abnormal noises from the chassis after parking: 1. Cooling noise from the catalytic converter: The normal operating temperature of the catalytic converter is 400-800°C. After the engine is turned off, its operation gradually stops, and the temperature decreases, causing the internal metal components to expand and contract due to heat, resulting in abnormal noises. 2. Cooling noise from the exhaust pipe: Typically, the exhaust pipe reaches temperatures above 200°C during cold idle. When the car is under high load or there is combustion of the air-fuel mixture in the exhaust pipe, the temperature can be even higher. Therefore, the exhaust pipe also undergoes thermal expansion and contraction, producing abnormal noises, often originating from the front end of the exhaust pipe and the flexible joint. 3. Cooling noise from the turbocharger: Under normal conditions, the exhaust gas temperature can reach 700°C, accelerating the friction-generated heat from the turbocharger's rapid rotation. After the engine is turned off, the thermal expansion and contraction are quite noticeable, leading to abnormal noises.