After the sagitar 20 13 1.4t stopped, it heard a sound similar to deflation, but it disappeared after a while. What happened?

This is no problem. It is normal. I found it after a while. Out of the way

It may be because of the sound when the water vapor in the waterway pushes the antifreeze into the water replenishment tank after the water temperature rises; After driving for a long time, it is recommended that you idle for a period of time, and then turn off the engine after the electronic fan stops working and the water temperature is normal. If the engine is turned off immediately, the internal temperature of the engine is still very high. After the engine stops suddenly, the water pump stops working, and the cooling water in the radiator can't circulate, so the water temperature will continue to rise after parking, which may lead to the phenomenon you mentioned.

I didn't see you bring a t just now, or it may be the sound of turbine pressure relief cooling. Many Volkswagen cars find this action, and it seems abnormal to wear a T without this sound.

Maybe both. You can have a try.