This expansion tank stores coolant that expands as the engine reaches operating temperature, and returns it to the cooling circuit when the system cools. It sits in the engine bay, connected to the radiator or heat exchanger by a hose at the top and a return line at the bottom. A crack or leak in the tank allows air into the system, which can cause localized hot spots and reduce cooling efficiency. The tank is molded to match the original mounting points and hose connections, so no adapters or modifications are needed during replacement. When installing, ensure the sealing gasket is clean and the cap is tightened to the specified torque.