This workshop service repair manual covers the David Brown AD4 25 engine, providing comprehensive information for its maintenance and repair. Designed for robust performance and reliability, the AD4 25 engine is a testament to David Brown's engineering heritage. This manual is intended to assist owners and technicians in understanding the intricacies of this engine, ensuring its continued operational excellence. The scope of this manual is extensive, encompassing all necessary procedures for the AD4 25 engine. It details maintenance schedules, diagnostic troubleshooting, repair techniques, and technical specifications. By following the guidelines within this document, users can effectively perform routine servicing, address potential issues, and undertake complex repairs, thereby maximizing the longevity and efficiency of their David Brown AD4 25 engine.