Genuine OEM Audi Coolant Hose, part number 80A145919C. This hose is an integral part of the engine cooling system, responsible for transferring coolant between various components to maintain optimal engine operating temperature. The diagram clearly shows it as a lower hose, connecting to the radiator and other cooling circuit pipes. Constructed from durable, flexible, and heat-resistant rubber, it measures approximately 0.5 meters in length. Selecting a genuine OEM coolant hose guarantees the correct internal diameter, precise routing geometry, and resistance to thermal cycling and pressure, which are essential for preventing leaks and ensuring long-term cooling system reliability.