This service repair manual covers Caterpillar 3304 and 3306 diesel engines. These engines are known for their robust construction and reliability, making them suitable for a wide range of demanding applications. The 3304 model offers a displacement of 6.6 liters with horsepower typically ranging from 90 to 150 HP, while the larger 3306 model features a 10.5-liter displacement and produces between 150 and 250 HP. Both engines utilize a liquid-cooled system and compression ignition. This comprehensive manual provides detailed information essential for the maintenance, repair, and diagnostics of your Caterpillar engines. It includes step-by-step procedures, detailed illustrations, drawings, and photos to guide you through various service tasks, including electrical system diagnostics and repair, fuel system maintenance, exhaust system servicing, and cooling system procedures. The manual also specifies recommended diesel engine oil and oil capacities for both the 3304 and 3306 models, ensuring optimal performance and longevity.