Coolant Expansion Tank Cap rated at 1.4 bar, fitted to the expansion (header) tank of the engine cooling system.

The cap seals the expansion tank and regulates system pressure. It holds the coolant under pressure to raise its boiling point, while a relief valve vents excess pressure once it exceeds the 1.4 bar rating, protecting the tank and hoses. An integral vacuum valve draws coolant back from the overflow as the system cools and contracts.