Genuine OEM Volkswagen Coolant Expansion Tank, part number 2Q0121407D. This vital component manages the volume changes of engine coolant as it heats and cools, ensuring the cooling system remains properly filled and pressurized. It is an integral part of the engine cooling system, typically located in the engine bay. Constructed from durable plastic, it weighs 0.542 kg and measures 0.23 m in length. Using a genuine OEM expansion tank guarantees the correct material properties and pressure relief valve specifications, preventing leaks and maintaining optimal engine operating temperatures.