| Parameter | Specification |
|---|---|
| COGENG Part Number | 878000490 |
| OEM Equivalent | Komatsu 878000490 |
| Product Type | Hydraulic Cylinder Seal Kit |
| Application | Backhoe Loader Hydraulic Cylinders |
| Kit Type | Complete overhaul seal kit |
| Brand | Part Number |
|---|---|
| COGENG | 878000490 |
| Komatsu | 878000490 |
| Interchange | 878000491, 878000492, 878000493 |
| Component | Material Grade | Hardness | Temperature Range |
|---|---|---|---|
| Piston Seals | Polyurethane (PU) | 90-92 Shore A | -35°C to +110°C |
| Rod Seals | NBR + PTFE coating | 85 Shore A | -40°C to +120°C |
| Wiper Seals | Polyurethane (PU) | 88-90 Shore A | -35°C to +100°C |
| O-Rings | HNBR (Zetpol) | 70 Shore A | -40°C to +150°C |
| Wear Rings | PTFE + Bronze filler | — | -50°C to +200°C |
| Backup Rings | Nylon 66 (Glass filled) | — | -40°C to +120°C |
| Buffer Seals | Polyurethane | 90 Shore A | -35°C to +110°C |
| Parameter | Rating |
|---|---|
| Maximum Pressure | 240 bar (3,480 psi) |
| Operating Temperature | -40°C to +120°C |
| Fluid Compatibility | Mineral oil, synthetic hydraulic fluids, biodegradable oils |
| Seal Speed Rating | Up to 0.5 m/s |
| Service Life | 5,000+ operating hours |
Machine Securement: Park the loader on a firm, level surface. Lower the bucket fully to the ground. Engage the parking brake and block the wheels. Relieve all hydraulic pressure by cycling controls with the engine off.
Cleanliness Protocol: Perform disassembly and assembly in a clean, enclosed area. Use a clean parts washer and lint-free wipes. Contaminants are the primary cause of premature seal failure in hydraulic systems.
Cylinder Handling: Mark hose connections and cylinder orientation before removal. Use proper hoisting equipment for heavy cylinders. Support the cylinder body during disassembly—do not clamp the chrome rod in a vise directly; use soft jaws or a rod protector.
Detailed Inspection: After disassembly, meticulously inspect the chrome rod for scratches, pitting, or wear (especially on the rod side facing the ground). Inspect the cylinder tube bore for scoring or corrosion. Minor imperfections can be polished with fine emery cloth; major damage necessitates rod re-chroming or tube honing.
Seal Installation Best Practices:
Lubricate Generously: Coat all seals and metal contact surfaces with clean hydraulic fluid prior to assembly.
Use Protection: Always use installation sleeves or rolled plastic over threads and sharp edges when sliding seals into place.
Correct Orientation: Ensure all directional seals (U-cups, lip seals) are installed facing the correct way—typically, the lip faces the pressure side. Refer to the kit diagram.
Avoid Stretching: Do not over-stretch O-rings or seals. Use proper seal picks or blunt tools to seat them evenly in their grooves.
Reassembly & Bleeding: Reassemble components in the reverse order of disassembly, following torque specifications for gland nuts, tie-rods, or end caps. After reconnecting hoses, slowly cycle the cylinder multiple times with the bucket slightly raised to purge trapped air from the system. Check and top up hydraulic fluid.
