This manual covers the David Brown AD4-25 Diesel Engine, a robust and reliable power unit designed for demanding applications. Engineered for durability and consistent performance, the AD4-25 is a testament to David Brown's commitment to quality in engine manufacturing. Its robust construction and efficient diesel technology make it a preferred choice for various industrial and agricultural uses where dependable power is paramount. The purpose of this service manual is to provide comprehensive guidance for the maintenance, repair, and servicing of the David Brown AD4-25 Diesel Engine. It details essential procedures, technical specifications, and troubleshooting steps necessary for optimal engine operation and longevity. This resource is intended for professional technicians, ensuring they have the knowledge to perform accurate diagnostics and effective repairs, thereby maintaining the engine's peak performance and extending its service life.