This manual covers the Caterpillar Cat S4S Diesel Engine, specifically for DP20N-35N and P4000-P7000 forklift trucks. Designed for demanding industrial applications, these engines are recognized for their robust construction and reliable performance. The engineering behind the S4S series emphasizes durability and efficiency, making them a trusted choice for heavy-duty material handling operations. This documentation provides comprehensive details on the systems and components that ensure the continued operational excellence of your Caterpillar equipment. The purpose of this service repair manual is to offer detailed guidance for the maintenance, inspection, and repair of the Caterpillar Cat S4S Diesel Engine. It includes essential technical specifications, diagnostic procedures, and step-by-step instructions for various service operations. By utilizing the information contained herein, owners, technicians, and mechanics can effectively maintain the engine's optimal condition, ensure safety, and prolong the service life of the forklift trucks. This manual serves as an indispensable resource for all aspects of engine care and repair.