The Nissens Engine Coolant Expansion Tank - 996267 is a replacement part for a vehicle's cooling system. It is designed to hold excess coolant fluid and allow for expansion as the engine heats up. This helps to prevent overheating and potential damage to the engine. The expansion tank is made of durable materials and is designed to fit specific vehicle models for easy installation. It is an essential component for maintaining proper engine temperature and ensuring the smooth operation of the vehicle.