This workshop service repair manual provides comprehensive information for the Komatsu 4D98E and 4TNE98T diesel engines. These robust, liquid-cooled, 4-cylinder in-line engines are designed for a wide range of industrial and heavy-duty applications, offering reliable performance with a displacement of 3.300 L. The 4D98E features natural aspiration, while the 4TNE98T is turbocharged, providing versatile power outputs typically ranging from approximately 50-65 kW. Engineered for durability and efficiency, these engines are a testament to Komatsu's commitment to quality and performance in demanding environments. This manual serves as an essential resource for owners, technicians, and mechanics, detailing all aspects of engine maintenance, repair, and technical specifications. It covers critical procedures such as lubrication, recommended oil viscosities (SAE 10W-30 or 15W-40, API CI-4 or higher), and typical service intervals, with oil capacity noted at approximately 7.0-7.5 liters. With hundreds of pages of detailed instructions and diagrams, this complete official factory manual empowers users to effectively maintain and troubleshoot the Komatsu 4D98E and 4TNE98T engines, ensuring their continued optimal operation and longevity.