This manual covers the David Brown AD4-25 and CAD4-30 Diesel Engine models. It is a comprehensive factory service and repair workshop manual designed to provide detailed information for these specific diesel engines. The manual focuses on the engineering and technical aspects of these engines, aiming to ensure their continued reliability and performance through proper maintenance and repair procedures. The purpose of this manual is to serve as a definitive resource for owners, mechanics, and technicians. It encompasses essential maintenance procedures, troubleshooting guides, detailed technical specifications, and critical safety guidelines relevant to the AD4-25 and CAD4-30 Diesel Engines. By following the instructions within this manual, users can effectively maintain, diagnose, and repair these engines, ensuring optimal functionality and longevity.