This manual covers the David Brown AD4 25 engine, a robust and reliable power unit designed for demanding applications. Engineered for durability and performance, the AD4 25 engine represents a significant achievement in its class, offering efficient operation and a long service life. Its design prioritizes ease of maintenance and dependable functionality, making it a preferred choice for various industrial and agricultural uses where consistent power delivery is essential. The purpose of this comprehensive service manual is to provide detailed information for the maintenance, repair, and troubleshooting of the David Brown AD4 25 engine. It includes essential technical specifications, step-by-step repair procedures, diagnostic guidance, and safety precautions. This resource is intended for owners, mechanics, and technicians to ensure the optimal performance and longevity of the engine through proper care and servicing.