155-5109 CAT Piston Pump for Loader 416C 426C 428C

Product Overview

The 155-5109 (Part Number: 1555109, cross-referenced with 185-5918 and 155-6657) is a high-pressure axial variable displacement piston pump engineered for Caterpillar (CAT) 416C, 426C, 428C, and 436C backhoe loaders. Manufactured to strict CAT OEM specifications, this hydraulic pump provides 100% drop-in mechanical, hydraulic, and control interchangeability. Constructed with a heavy-duty ductile iron housing and high-precision bimetallic rotating groups (cylinder block, pistons, valve plate, and swashplate), it delivers outstanding volumetric efficiency and low noise performance under demanding excavator/loader duty cycles. Every pump undergoes 100% factory bench testing under simulated full-load operating pressure and flow conditions to guarantee a direct, reliable replacement for original Caterpillar hydraulic pumps.

Technical Specifications 

• Full Part Numbers: 155-5109 / 1555109 (Cross-ref: 185-5918, 155-6657)

• Compatible Machinery: Caterpillar (CAT) 416C, 426C, 428C, 436C, 416D, 420D, 424D Backhoe Loaders

• Pump Type & Control: Axial Variable Displacement Piston Pump with Load Sensing / Pressure Compensated Control

• Max Displacement: Approx. 75 cm³/rev

• Rated Operating Pressure: 250 bar (25 MPa)

• Peak Pressure: 280 bar (28 MPa)

• Max Operating Speed: 2200 RPM

• Rotation: Clockwise (CW, viewed from shaft end)

• Drive Shaft Spec: Standard multi-tooth splined shaft

• Net Weight: Approx. 36.5 kg

Key Technical Advantages

• 100% Drop-In CAT OEM Fit: Mounting flanges, splined drive shafts, main SAE port locations, and LS sensing ports strictly match original CAT specifications for seamless plug-and-play installation.

• Bimetallic Valve Plate & High Efficiency: The cylinder block and valve plate feature bronze-on-steel sintered metallurgy with super-finished sliding surfaces, minimizing internal leakage and sustaining over 94% volumetric efficiency.

• High-Response Load Sensing (LS) Control: Features an integrated pressure/flow compensator valve that automatically adjusts output based on load demand, lowering fuel consumption and smoothing multi-function digging/loading operations.

• 100% Factory Simulated Load Tested: Every unit is validated on automated test benches for pressure holding, maximum flow, and compensator response across full temperature ranges before shipment.

Application Areas

• Backhoe Loader Main Hydraulic Power: Main hydraulic pump for boom lift, stick extension, bucket curl, and front loader functions on CAT 416C, 426C, 428C, and 436C machines.

• Auxiliary Hydraulic Attachment Drive: Provides stable high-pressure oil supply for auxiliary hydraulic tools such as hydraulic breakers, compactors, and augers.

Expert Maintenance Tips

• Flushing & Filter Replacement: Prior to installation, thoroughly flush the main hydraulic reservoir and lines. Always replace both the suction and return filter elements to prevent residual metal debris from scoring new rotating components.

• Mandatory Case Priming: Fill the pump casing with clean hydraulic oil (approx. 1.5 to 2.0 liters) through the top drain port before cranking the engine to prevent dry-start damage to swashplates and piston shoes.

• Air Bleeding & Low-Idle Break-In: Run the engine at low idle with no hydraulic load for 5–10 minutes after start-up to purge trapped air from the system. Verify pilot and system pressure stability before subjecting the machine to full working loads.