The Expansion Tank (OEM Number 9705000349) for Mercedes-Benz Trucks is a vital component of the vehicle’s cooling system, designed to regulate coolant expansion and maintain stable pressure in heavy-duty applications. Used in models like the Actros, Atego, and Axor (2005 onward) with engines such as the OM 926 or OM 470, it stores excess coolant during engine heat-up to prevent over-pressurization and returns coolant as temperatures drop, ensuring optimal fluid levels. Constructed from high-strength, heat-resistant plastic, it features a translucent body for easy visual monitoring of coolant levels and a pressure-rated cap (typically 1.4–1.6 bar) to uphold system integrity. With a capacity of approximately 3–4 liters, it integrates into the engine bay via rugged, OEM-specific mounting brackets and reinforced hose connections. This tank minimizes air ingress, reduces coolant loss, and prevents overheating, protecting critical components like the radiator, water pump, and engine block. Its corrosion-resistant design and durable construction ensure reliability in long-haul, high-mileage, or extreme operating conditions.