There are some expansion kettles in that kettle, which directly participate in engine cooling. If it is missing, it needs to be added to the specified scale. If it is a water replenishing kettle, it will replenish water to the water tank, that is, it will replenish water to the water tank when there is water shortage. It doesn't matter if you lose it. There is water in the water tank. If it is almost used up, you need to add antifreeze.