geniushanbiao 写了: 2025年 8月 24日 12:43
This one is called recovery tank, not expansion tank. Expansion tank is in series in the coolant system and withstands pressure when engine is warmed up. The recovery tank does not withstand any pressure.
Agreed. I was not being precise. I think people also call this overflow tank. For people, who knows how these things work, there is no ambiguity.
The tank in the picture is obviously open to air. The cooling system is pressurized. In this type of design there is a spring loaded valve that opens at the operating pressure to let coolant out. At negative pressure (say -0.1) bar, the valve also let coolant from this tank to refill the cooling system.
This tank can be used to top off coolant only if the cooling system is properly filled and the tank is not below the inlet tube. If the cooling system does not hold pressure, it won't be able to suck coolant from this tank.
To see if the coolant recovery tank is actually the highest point, one only needs to open the hood and see if the top of the radiator or the fill line of the tank is higher. It does not need rocket science. Most coolant recovery tank is not the highest point of the cooling system.