What is the reason why the car makes a cooing sound when it is turned off?

There will be water noise when the car is turned off, because there is gas in the cold exhaust pipe to be re-ignited. Maybe the tank is boiling. During driving, the engine and exhaust pipe will generate high heat, which is easily transferred to its fuel tank. This heat will increase the pressure of the gasoline vaporization tank, and this part of the pressure and gasoline vapor will be stored in the activated carbon tank through the pipeline and burned again after starting. In order to avoid air pollution, some noise will be generated when the gas flows. In fact, this state has always existed and is a normal phenomenon. What should I pay attention to when the car stalls and there is water noise? 1. The automatic stall is mainly caused by the use of inferior fuel. First, increase high-quality oil in regular large gas stations, such as using 97 # gasoline. Although the price is much higher, it can guarantee the longer service life and good driving force of the car. 2. Thoroughly clean the oil circuit, including the fuel injector, throttle valve and fuel tank. It may be that the quality of the added oil is not enough, there is too much gum, the oil circuit is blocked and the oil circuit is not smooth.