The document provides instructions for disassembling and assembling a piston pump (hydraulic fan) on an excavator. It outlines 30 steps to disassemble the pump, removing components like the head, port plate, bearings, pistons, and shaft. It then lists 27 steps to reassemble the pump, installing these components in reverse order while taking precautions for spring-loaded parts. The instructions specify using the proper tools and cleaning procedures.