Bulldozer Komatsu D65PX-12 D65EX-12 D85-12 Hydraulic Pump Main Pump Piston Pump 708-1L-00011 708-1L-00012 708-1L-01011

The main pump of the D65 (D65EX / D65PX / D65WX series) serves as the power source for the entire hydraulic system. This axial variable displacement piston pump converts engine power into high-pressure oil, supplying the blade lift/tilt/tip, ripper, and steering functions. On the Komatsu D65 platform, the main pump is typically a piston pump assembly under the "708" series part numbering.

• Weak movement / slow operation of all functions: Worn pistons, valve plate, or slippers in the main pump causing internal leakage and reduced volumetric efficiency. First check system pressure and case drain flow to diagnose.
• Pump abnormal noise / squealing: Insufficient suction or air ingress (low oil level, blocked suction filter, leaking hose), contaminated oil, or internal pump wear.
• Engine lugging / speed drop under load: Seized regulator/power control valve; pump stays at large displacement and absorbs excessive power.
• High oil temperature: Severe main pump internal leakage, with high-pressure oil converting to heat.
• Main shaft oil seal leakage: Aged seal, excessive case pressure, or misaligned coupling.
• Jitter / pressure fluctuation: Air in the system, seized regulator, or scored valve plate.

• Light wear: Lap the valve plate, replace pistons, slippers, ball joint and seal kit, and clean the regulator.
• Severe scoring: Replace the rotating group parts or the complete main pump assembly.
• When ordering: Confirm the D65 sub-model (-12 / -15 / -16) and the original old part number (part numbers differ by generation and are not interchangeable).

Important: After repair, always replace all filters and clean the oil tank; otherwise, impurities will quickly damage the new pump.