The O-ring with code K 21406 is a vital sealing element in the ZV40/48 diesel engine, specifically designed for the cylinder liner interface. Its primary function is to create a pressure-tight seal between the liner and the engine block, preventing the escape of combustion gases and the ingress of coolant into the combustion chamber. Manufactured from high-temperature and chemically resistant elastomer, this O-ring withstands extreme engine conditions while maintaining flexibility and integrity. It plays a crucial role in ensuring proper engine compression and preventing efficiency losses due to internal leaks.