Genuine OEM Lexus Engine Water By-Pass Hose, part number 1629636030. This hose plays a vital role in the engine's thermal management by allowing coolant to bypass the radiator when necessary, such as during engine warm-up, to help the engine reach its optimal operating temperature more quickly. It is part of the engine's coolant circulation system. Constructed from durable rubber, it ensures reliable performance and longevity. Genuine OEM hoses are essential for by-pass systems to maintain the correct internal diameter and flexibility, ensuring efficient coolant flow and preventing premature engine wear.