This service manual provides comprehensive information for the Leyland 38TD and 4/98NT engines. These engines are known for their robust engineering and reliability, designed for demanding applications where consistent performance is paramount. This manual serves as a definitive guide to understanding, maintaining, and repairing these power units, ensuring their continued operational efficiency. The scope of this manual covers essential areas for engine upkeep and technical understanding. It details routine maintenance procedures, provides critical technical data, and offers in-depth guidance on the cylinder head, cylinder block, lubrication system, cooling system, and fuel system. By following the instructions and specifications within this manual, owners, mechanics, and technicians can effectively perform necessary services, diagnose issues, and ensure the longevity and optimal performance of the Leyland 38TD and 4/98NT engines.