A plastic radiator surge tank is an integral part of the cooling system. Pressurized coolant enters the tank through the surge tank inlet hose coming from the radiator. The coolant circulates in the tank. As the coolant circulates in the tank, air is allowed to bubble out. The coolant then exits from the tank outlet hose and flows to the water pump.

During vehicle use, the coolant heats and expands. The coolant that is displaced by this expansion flows to the surge tank. The tank is mounted at a point higher than all of the other coolant passages in order to provide air or vapor bleed that exceeds the pressure cap rating. When the coolant is cold, the level of the coolant should be at the appropriate mark on the tank.

The surge tank uses a low coolant indicator switch inside the surge tank. This indicator is serviceable only by replacing the surge tank.