This manual covers the David Brown AD4-25 and CAD4-30 diesel engines. These engines are known for their robust construction and reliable performance, making them suitable for a variety of demanding applications. Their engineering emphasizes durability and efficient operation, ensuring consistent power delivery across their operational lifespan. This comprehensive service manual provides detailed information essential for the maintenance, repair, and troubleshooting of the David Brown AD4-25 and CAD4-30 diesel engines. It includes in-depth procedures, technical specifications, and guidance to assist owners, mechanics, and technicians in preserving the optimal functionality and longevity of these engines.