| Parameter | Value / Specification |
|---|---|
| Maximum System Pressure | Up to 3,625 PSI (250 bar) |
| Temperature Range | -40°F to 225°F (-40°C to 107°C) |
| Fluid Compatibility | Mineral-based hydraulic oils, Komatsu-approved fluids, standard AW/HLP fluids |
| Primary Seal Material | Polyurethane (AU) & Nitrile Rubber (NBR) |
| Seal Hardness (Dynamic) | 88-92 Shore A (Polyurethane) |
| Seal Hardness (Static) | 70 Shore A (NBR O-Rings) |
| Design Standard | Engineered to meet Komatsu's original specifications for performance, durability, and fit. |
| Komatsu Machine Model | Specific Application |
|---|---|
| Komatsu WB140PS-2N | Stick (Dipper) Arm Cylinder |
| Komatsu WB150-2 | Stick (Dipper) Arm Cylinder |
| Note: | This kit is a direct replacement for Komatsu OEM part number 878000491. It is designed specifically for the STICK/ARM CYLINDER on the listed backhoe loader models. Always verify your machine's model, serial number, and that you are servicing the correct cylinder (Stick/Arm, not Boom or Bucket) before installation. |
| Component Name | Material | Color | Durometer | Function |
|---|---|---|---|---|
| Piston Seal (U-Cup) | Polyurethane (AU) | Brown | 90 Shore A | Main dynamic pressure seal on piston |
| Rod Seal (Step Seal) | Cast Polyurethane (CU) | Black | 90 Shore A | Primary rod seal for pressure retention |
| Wiper/Scraper | Polyurethane (PU) | Black | 85 Shore A | Excludes dirt, grit, and moisture |
| Buffer Ring | Polyurethane (CU) | Black | 88 Shore A | Protects rod seal from pressure spikes |
| O-Ring Set (Assorted) | Nitrile Rubber (NBR) | Black | 70 Shore A | Static sealing for gland, ports, plugs |
| Wear Ring / Guide Band | Filled PTFE / Nylon | Brown / White | N/A | Guides piston, prevents metal contact |
| Backup Rings | Nylon | Tan | N/A | Prevents O-ring extrusion under pressure |
| 395002004 | Arm cylinder | 1 | |
| 1 | 395067011 | • Cylinder | 1 |
| 2 | 500217005 | • Bushing | 2 |
| 3 | 500044300 | • Spacer | 1 |
| 4 | 801920220 | • Nut | 1 |
| 5 | 395275013 | • Piston | 1 |
| 6 | 391575011 | • Bushing | 1 |
| 7 | 395188011 | • Rod | 1 |
| 8 | 500217006 | • Bushing | 1 |
| 9 | 395303011 | • Cylinder head | 1 |
| 878000491 | • Gasket kit | 1 | |
| 10 | •• Gasket | 1 | |
| 11 | •• Ring wear | 1 | |
| 12 | •• O Ring | 2 | |
| 13 | •• Ring | 2 | |
| 14 | •• O Ring | 1 | |
| 15 | •• Scrapper ring | 1 | |
| 16 | •• Gasket | 1 | |
| 17 | •• Scraper ring | 1 |
Safe Depressurization & Support: Park the machine on level ground. Lower all attachments (bucket, stabilizers, backhoe) to the ground to relieve hydraulic pressure.
Clean Workspace: Perform all work in a meticulously clean environment to prevent contamination of the hydraulic system.
Documented Disassembly: Carefully disassemble the cylinder. Photograph and label each component and its orientation.
Mandatory Metal Inspection: Thoroughly inspect the cylinder rod for scratches, pitting, or scoring. Inspect the cylinder bore for wear or damage. Replace any damaged metal components before installing new seals.
Proper Seal Installation: Lubricate all new seals with clean hydraulic fluid. Use seal installation tools (cone tools, sleeves) to guide seals over threads and sharp edges without damage.
Precision Reassembly: Follow the included diagram for correct seal order and orientation. Ensure all seals are fully seated in their grooves.
Torque Specifications: Use a calibrated torque wrench. Adhere strictly to Komatsu's specified torque values and sequences for all fasteners (gland bolts, tie-rods)
