What is hot is on the top and what is cold is on the bottom.
The car water tank has two water pipes, upper and lower. One end of the water supply pipe is connected to the water tank upper water chamber, and the other end is connected to the water outlet of the engine water channel water pump. One end of the sewer pipe is connected to the sewer chamber of the water tank, and the other end is connected to the water inlet of the engine water channel. This creates a cooling water cycle in which the engine enters from the bottom and exits from the top, and the water tank enters from the top and exits from the bottom.