155-5109 CAT Hydraulic Piston Pump 250Bar 75cc

Product Overview

The 155-5109 (cross-referenced with part numbers 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 in strict accordance with Caterpillar OEM engineering standards, this hydraulic pump delivers 100% drop-in mechanical, hydraulic, and control line interchangeability. Built with a high-strength ductile iron housing and precision bimetallic rotating components (bronze-on-steel valve plate, hardened steel pistons, and swashplate assembly), it maintains high volumetric efficiency and quiet operation under severe heavy-duty digging and loading cycles. Every pump undergoes 100% factory bench testing under simulated full-load pressure and flow conditions to guarantee a direct, reliable replacement for original CAT pumps.

Technical Specifications 

• Full Part Number: 155-5109 (Cross-ref: 185-5918, 155-6657)

• Nominal Displacement: 75 cm³/rev

• Rated Operating Pressure: 250 bar (25 MPa)

• Peak Operating Pressure: 280 bar (28 MPa)

• Max Operating Speed: 2200 RPM

• Control Mode: Load Sensing / Pressure Compensated Control (LS/PC)

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

• Drive Shaft Specification: SAE standard multi-tooth splined shaft

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

• Net Weight: Approx. 36.5 kg

Key Technical Advantages

• 100% Drop-In CAT OEM Fit: Mounting flanges, splined drive shafts, main SAE port flanges, and LS signal ports match CAT specifications precisely for plug-and-play field replacement.

• Bimetallic Valve Plate & High Volumetric Efficiency: The cylinder block and valve plate feature sintered bronze-on-steel metallurgy with super-finished running surfaces, minimizing fluid blow-by and maintaining over 94% volumetric efficiency.

• High-Response Load Sensing (LS) Control: Integrated pressure/flow compensator valve dynamically adjusts output based on load demand, cutting fuel consumption and smoothing multi-function loader and backhoe movements.

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

Application Areas

• Backhoe Loader Main Hydraulic Systems: Primary hydraulic power source for front loader lift/tilt, rear backhoe boom/stick/bucket, and steering functions on CAT 416C, 426C, 428C, and 436C machines.

• Auxiliary Hydraulic Attachment Drive: Delivers steady high-pressure oil flow for auxiliary hydraulic tools such as hydraulic hammers, compactors, and augers.

Expert Maintenance Tips

• System Flushing & Filter Replacement: Thoroughly flush the hydraulic oil reservoir and main lines before installing the new pump. Always replace both the suction and return filter elements to prevent residual metallic wear particles from scoring new internal components.

• Mandatory Case Priming: Fill the pump housing with clean hydraulic oil (approx. 1.5 to 2.0 liters) through the upper drain port prior to initial engine start-up to prevent dry-start damage to the swashplate and slipper pads.

• Low Idle Break-In & Air Purge: Run the engine at low idle with zero hydraulic load for 5 to 10 minutes post-installation to purge trapped air from the hydraulic circuit. Confirm stable pressure readings before subjecting the machine to full workload.