This workshop service repair manual covers the David Brown AD4 25 and CAD4 30 engine models. These engines are recognized for their robust engineering and reliable performance, designed to meet demanding operational requirements. This manual provides comprehensive information to ensure these engines continue to operate at peak efficiency. The purpose of this manual is to serve as a complete guide for maintenance, repair, and troubleshooting. It includes detailed procedures, technical specifications, and essential safety guidelines. Owners, mechanics, and technicians will find the information within this manual invaluable for understanding and maintaining the David Brown AD4 25 and CAD4 30 engines, ensuring their longevity and optimal functionality.