Genuine OEM Audi Engine Expansion Tank Vent Hose, part number 8K0121086AA. This hose plays a vital role in the engine cooling system by allowing trapped air to escape from the coolant expansion tank, preventing air pockets that can hinder cooling efficiency. It connects directly to the expansion tank and other cooling system components. Measuring 0.64 meters in length and weighing 0.25 kg, it is constructed from high-quality, heat-resistant rubber or plastic. Using a genuine OEM hose guarantees correct routing, material compatibility, and a secure, leak-proof connection, essential for maintaining optimal engine temperature.