Case W8, W9, W9A, W10, W12 Loader Repair Manual

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Manual Extract Introduction Hydraulic Pump
General

The 25X Series Hydraulic pump used on the Unit Loaders is a flange mounted, gear type, fixed displacement pump, mounted to and driven by the converter. The hydraulic pump operates continuously whenever the Loader engine is running, drawing filtered hydraulic oil from the reservoir and circulating the oil through the system, the return filter and back into the reservoir.

Pump Body

The hydraulic pump body is cast in three sections for ease in disassembly, cleaning, inspection and servicing. The pump body is cored and drilled for installation of “0” rings, oil seals, bearings and check valves. The three sections of the pump body are held together by four caps crews to form an oil tight housing for the pump gears.

Pump Gears

Two gears are contained in the pump assembly, a drive gear and a driven gear. As the gears of the hydraulic pump revolve, the hydraulic oil drawn from the reservoir is trapped between the gear teeth and forced from the inlet, or suction, side of the pump through the small openings between the gear teeth and pump body, to the outlet, or pressure, side of the pump. The hydraulic oil is prevented from returning to the inlet side of the pump by the close mesh of the pump gears and the small clearance between the gears, pump body and the pump cover. The both gears are a matched set, therefore, both gears must be replaced if replacement is ever necessary.