This service repair workshop manual provides comprehensive information for the Mitsubishi 4D55 Engine. This diesel engine, part of the Sirius family, features an inline 4-cylinder configuration with a SOHC valvetrain. It offers a displacement of 2300cc, a bore of 91.1mm, and a stroke of 87.0mm, with a compression ratio of 21.0:1. Known for its robust engineering and reliability, the 4D55 engine typically produces approximately 70-75 horsepower and 140-150 Nm of torque, utilizing indirect injection and liquid cooling. While specific vehicle applications and production years are not detailed, this manual covers the essential aspects of its mechanical operation. The purpose of this English-language manual is to offer full service and repair instructions for the Mitsubishi 4D55 Engine. It details critical maintenance procedures, including oil capacity (approximately 5.7 liters), oil filter type, and timing belt replacement intervals. Furthermore, it covers the operation and maintenance of components such as glow plugs, fuel filters, and the cooling system, specifying ethylene glycol-based coolant. This resource is designed to assist owners, mechanics, and technicians in effectively maintaining, diagnosing, and repairing the engine, ensuring its continued performance and longevity.