The Ford Transit Expansion Tank (Part Number 40422332) is a vital component of the vehicle’s cooling system, designed to manage coolant expansion and contraction during engine operation. Typically used in Ford Transit models like the Mk6 (1995–2006) with 2.0L and 2.4L diesel engines, it stores excess coolant when the engine heats up, preventing overflow and pressure spikes, then returns coolant as temperatures drop to maintain optimal levels. Constructed from durable, heat-resistant plastic, it features a translucent body for easy fluid-level monitoring and includes a pressure-rated cap (usually 15–16 psi) to ensure system integrity. With a capacity of approximately 1–1.5 liters, it integrates seamlessly into the engine bay with OEM-specific mounting points and hose connections. This tank minimizes air ingress, reduces coolant loss, and protects against overheating, safeguarding critical components like the radiator and water pump. Its corrosion-resistant design ensures longevity, making it essential for maintaining reliable cooling performance in commercial and heavy-duty Transit applications.