This manual covers the Komatsu 108 Series Diesel Engine, specifically engine models S6D108-1 and SA6D108-1. These robust diesel engines are integral to a range of heavy machinery, including models such as the D57S-1, WA320-3, WA380-3, EG150BS-5, PC300-5, PC300HD-5, PC360LC-5, WA420-3, AUSTOFT (10001 - 10926), AUSTOFT (10927 - Above), EG185B-L-1, and DENYO DCA 180. Engineered for demanding applications, the Komatsu 108 Series is recognized for its reliability and performance in various industrial and construction environments. The purpose of this Service Repair Manual is to provide comprehensive information for the maintenance and repair of the specified Komatsu diesel engines. It details procedures for General Information, Engine Mechanical, Fuel System, Exhaust System, Cooling System, Lubrication System, Electrical System, Intake System, and Preheating System. This document is an essential resource for owners, technicians, and mechanics, enabling them to perform routine maintenance, diagnostics, and repairs effectively, thereby ensuring the continued optimal operation and longevity of the engine.