What does it mean when the Audi A4's engine keeps running after turning off?

[BeauDella]

Because the water temperature inside the engine hasn't dropped immediately, the radiator fan continues to operate for cooling. Once the appropriate water temperature is reached, the fan stops. In other words, even after the car is turned off, the fan may still be working. More details are as follows: 1. The car has an automatic cooling function: After parking, if the engine temperature is too high, the fan will automatically turn on to continue cooling the engine. Once the engine temperature drops to a reasonable level, the fan will stop automatically. 2. A "pop pop pop" sound from under the car: Some owners might hear a "pop pop pop" sound from under the car after parking and turning off the engine. The "culprit" is actually the three-way catalytic converter located at the rear of the vehicle's chassis. This component operates at temperatures close to 1000 degrees Celsius, and after turning off the engine, the metal parts inside expand and contract due to heat, producing some popping sounds. 3. The role of the three-way catalytic converter: It is a purification device in the exhaust system that converts harmful substances in the exhaust into carbon dioxide, water, and nitrogen, reducing harmful gas emissions.