This manual covers the David Brown AD4-25 and CAD4-30 Diesel Engines. These engines are known for their robust construction and reliable performance, designed to meet the demanding requirements of various industrial and agricultural applications. Their engineering prioritizes durability and efficiency, making them a trusted choice for operators who depend on consistent power and longevity. The purpose of this Factory Service Repair Manual is to provide comprehensive guidance for the maintenance, repair, and servicing of the David Brown AD4-25 and CAD4-30 Diesel Engines. It includes detailed procedures, technical specifications, and diagnostic information essential for ensuring optimal engine operation and longevity. This resource is intended for owners, mechanics, and technicians to effectively maintain and troubleshoot these engines.