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Key Features:
Multi-Model Compatibility: A single kit services boom, bucket, and steering cylinders across 6+ popular Komatsu wheel loader models, simplifying parts inventory.
DuraShield™ Compound Technology: Specially formulated elastomers provide 30% better abrasion resistance and superior resilience against cold cracking compared to standard NBR.
Universal Design with Precision: Engineered to accommodate slight dimensional variances between models while maintaining exact sealing performance in each application.
Complete Overhaul Solution: Includes every dynamic and static seal, O-ring, guide, and wiper needed for a full cylinder rebuild on compatible models.
Optimized for Loader Duty Cycle: Seals are designed to handle the rapid cycling and high side loads characteristic of loader bucket and lift operations.
| Parameter | Specification / Value |
|---|---|
| COGENG Part Number | CGK-8780-492MU (Multi-Use) |
| Replaces OEM Number | 878000492 (Komatsu) |
| Primary Seal Material | DuraShield™ (Aramid-fiber reinforced HNBR) |
| Wear Band Material | Oil-filled Nylon (Oilon) with low-friction coating |
| Operating Temperature Range | -35°C to +120°C (-31°F to +248°F) |
| Maximum System Pressure | 32 MPa (4,640 psi) |
| Cycle Life Rating | >500,000 full-stroke cycles at 25 MPa |
| Fluid Compatibility | Komatsu TDTO, ISO VG 46/68, Universal Tractor Fluid (UTF) |
| Seal Hardness | 88±5 Shore A (Dynamic Seals) |
| Storage & Shelf Life | 5 years in UV-protected packaging at <30°C |
| Component Name | Material & Specification | Qty per Kit | Function & Design Advantage |
|---|---|---|---|
| Main Piston U-Seal | DuraShield™ HNBR with internal garter spring | 2 | Primary pressure seal; spring ensures constant lip contact at varying pressures. |
| Rod Seal (Step-Seal) | DuraShield™ HNBR with integrated anti-extrusion heel | 2 | Two-piece design provides excellent leakage control and handles pressure reversals. |
| Rod Wiper/Scraper | Polyurethane (PU) with steel reinforcement ring | 2 | Positive lock design prevents pop-out; dual lips for scraping and fine sealing. |
| Piston Wear Band | Oil-filled Nylon (Oilon), self-lubricating | 4 | Reduces friction, supports piston load, and withstands deformation. |
| Rod Wear Band | Oil-filled Nylon (Oilon) | 2 | Provides stable rod guidance, minimizing side load on the rod seal. |
| Buffer/Secondary Seal | Standard HNBR, pressure-activated design | 2 | Captures internal leakage, protecting the primary rod seal. |
| Static O-Ring Kit | Nitrile (NBR-70), color-coded by size | 15 pcs (8 sizes) | Covers all port, gland, and plug sealing points across all models. |
| Back-up Rings | Teflon® PTFE | 4 | For use behind piston seals in models with larger groove clearances. |
| Thread Protectors | Soft PVC | 2 | Reusable caps to protect rod threads and chrome surface during handling. |
This universal kit is designed for the following Komatsu wheel loader models. It is primarily used for boom (lift) and bucket (tilt) cylinders.
| Loader Model Series | Specific Models Covered | Primary Cylinder Application | Notes |
|---|---|---|---|
| WB91R Series | WB91R-2, WB91R-2E0 | Boom & Bucket Cylinders | Primary application |
| WB93R Series | WB93R-2, WB93R-2E0 | Boom & Bucket Cylinders | Primary application |
| WB97R/WB97S | WB97R-2, WB97S-2 | Boom & Bucket Cylinders | Seal profiles identical |
| WB140 Series | WB140-2, WB140-2N | Bucket (Tilt) Cylinders ONLY | For boom cylinders, use model-specific kit |
| WB150 Series | WB150-2, WB150-2N | Bucket (Tilt) Cylinders ONLY | Verify cylinder diameter before use |
Critical Compatibility Note: While this kit is listed for multiple models, cylinder bore and rod sizes can differ between the boom and bucket functions on the same machine, and between models. Always match the physical dimensions and profile of the old seals with the new ones in the kit prior to disassembly. The WB140/WB150 application is typically for the smaller bucket cylinders, not the larger boom cylinders.
Phase 1: Pre-Work Verification & Safety
Model & Cylinder Verification: Before ordering, confirm your loader model, serial number, and whether the cylinder is for Boom (Lift) or Bucket (Tilt). Measure the old rod diameter if possible. Mismatch leads to immediate failure.
Workspace Setup: Perform the rebuild in a clean, dust-free area. Cover the workbench with a clean plastic sheet. Have a dedicated container for hydraulic fluid to flush the cylinder.
Phase 2: Disassembly & Critical Inspection
3. Cylider Identification: Mark the cylinder ("Left Boom", "Right Tilt") and its orientation before removal. Tag all hoses.
4. Contamination Control: Before opening, clean the exterior thoroughly. Upon disassembly, place components on a clean tray—never on the floor or dirty bench.
5. Wear Measurement: Use a micrometer to measure the rod diameter at several points, especially where the seal contacts. Acceptable wear: Max 0.05mm taper or reduction. Use a bore gauge to check the cylinder tube for ovality (>0.1mm is unacceptable).
6. Groove Inspection: Check seal grooves in the piston and gland for nicks, corrosion, or wear. Damaged grooves must be repaired or the component replaced.
Phase 3: Assembly & Installation
7. Preparation of Parts: Wash all metal components in clean solvent and dry with lint-free air. Lightly polish the rod with 400-grit or finer emery cloth in a longitudinal motion (never circular) to remove glaze or minor imperfections.
8. Seal Installation Order:
* On the Gland: Install the rod wear band first, followed by the buffer seal, then the primary rod step-seal. Use a deep socket of appropriate size to evenly press the seals into their grooves.
* On the Piston: Install the wear bands, then the main piston U-seal. Ensure the garter spring is properly seated and not twisted.
9. Key Installation Rule: Lubricate every seal and metal surface with the same hydraulic fluid that is in the machine during assembly. Do not use grease or incompatible oils.
10. Final Assembly: When inserting the piston into the tube and the rod into the gland, use the provided PVC thread protectors and a steady, straight motion to avoid damaging seals.
Phase 4: Post-Installation & Testing
11. Initial Filling & Bleeding: After reassembly, connect the hydraulic hoses. With the cylinder ports pointed upwards, manually fill it with fluid through a service port if available. This minimizes air pockets.
12. Air Purging Procedure: Start the engine and run at low idle. Slowly cycle the cylinder fully in and out 5-10 times. Listen for "chattering" or observe jerky movement, which indicates air. Continue until motion is smooth.
13. Leak Check & Run-In: Inspect for external leaks at seals and ports. Operate the loader under normal loads for 1-2 hours, then re-check seal areas and hydraulic fluid temperature. Allow a 24-hour "seat-in" period for seals before subjecting to maximum pressure.
Warranty: 18-month limited warranty against manufacturing defects. Warranty is void if seals are installed on visibly worn/damaged rods or tubes, or if improper fluid is used.
