This Service Manual covers the David Brown Diesel Engine AD4-25. This engine is renowned for its robust construction and reliable performance, making it a dependable choice for various applications. Engineered with precision, the AD4-25 embodies David Brown's commitment to quality and durability, ensuring efficient operation and longevity in demanding environments. Its design prioritizes both power and fuel efficiency, reflecting a balanced approach to engine development. The purpose of this manual is to provide comprehensive guidance for the service, repair, and maintenance of the David Brown Diesel Engine AD4-25. It details essential procedures, technical specifications, and troubleshooting steps to assist owners, technicians, and mechanics in keeping the engine in optimal working condition. By following the information contained herein, users can effectively perform routine maintenance, diagnose issues, and execute repairs, thereby ensuring the continued reliability and performance of their AD4-25 engine.