707-99-67090 Excavator Arm Cylinder Seal Kit for Komatsu PC300-7
Excavator Arm Cylinder Seal Kit Product Overview
The 707-99-67090 Seal Kit is engineered exclusively for Komatsu PC300-7 /8 and PC300LC-7 /8 excavators hydraulic arm (stick) cylinders repair. This OE-equivalent solution restores critical hydraulic sealing to prevent pressure loss during heavy digging and lifting operations.
707-99-67090 Seal Kit Technical Specifications
| Komatsu Models | PC300-7 / 8, PC300LC-7 / 8 (Arm Cylinder Repair Kit) |
| Cylinder Dimensions | Rod: 105mm (4.13″) |
| Operating Pressure | 34.3 MPa (4,975 PSI) w/ 40MPa Peak Tolerance – Meets Komatsu Standards |
| Temperature Range | -40°C to +120°C (-40°F to +248°F) – depends on the material, Support custom |
| Seal Materials | Primary Seals: Cast Polyurethane (Grade 5AU) |
| Critical Components | HNBR O-Rings, Anti-Extrusion Washers (Bronze-Filled PTFE), Purple Polyurethane Wiper |
| Compatibility | Fluids: Komatsu BIO HF-2/HF-3, KES 07.881 Mineral Oils |
The Excavator Arm Seal Kit Main Components
| Pressure-Actuated U-Cups Seal | Double-lip directional design resorts seal extrusion at rod angles >8° |
| Load-Bearing Buffer Rings | PTFE composite prevents U-cup damage under 140MPa localized stress |
| Multi-Stage Wiper | Purple polyurethane triple-lobe design excludes abrasive particles >15 microns |
| Rod Guide Band | Sintered bronze with PTFE coating minimizes friction-induced scoring |
| HNBR Seals | Bio-oil resistant (SAE J200 Type CH) for PC300-7’s closed-loop hydraulic circuit |
| Anti-Wear Rings | Prevents gland wear during cylinder misalignment |
707-99-67090 Arm Seal Kits Key Features
✅ Standard or OEM: Direct replacement for Komatsu PC300-7 / 8, PC300LC-7 / 8 excavators arm cylinders repair
✅ Heavy-Duty Pressure Handling: 34.3MPa dynamic rating exceeds PC300-7 operating specs
✅ Impact & Vibration Resistance: Polyurethane seals absorb shock loads during rock digging
✅ Abrasion Defense: Wiper lifespan 2.5x rubber seals in slurry environments
✅ -40°C Low-Temp Flexibility: Eliminates brittle fractures in Arctic operations
✅ Corrosion Protection: HNBR compounds resist acidic hydraulic fluid breakdown
Related Products
A: This kit is primarily designed for the PC300-7/8 and PC300LC-7/8 arm cylinders. It may also fit PC400-7 and PC400LC-7 excavators that share the same 105mm rod diameter arm cylinder configuration. Always measure your cylinder bore and rod diameter before ordering. Contact DJF with your machine serial number for compatibility verification if you are unsure.
Q: How do I verify the correct dimensions before installing this kit?
A: Before disassembly, confirm your arm cylinder rod diameter measures exactly 105mm (4.13 inches). The cylinder bore should be 160mm. Inspect the gland area for any casting marks or part numbers that match the Komatsu PC300-7 or PC300-8 series. If the dimensions differ or you find significant rod scoring, contact DJF for a custom seal solution.
Q: Can this kit handle Komatsu BIO HF-2 biodegradable hydraulic fluid?
A: Yes. The HNBR seals in the 707-99-67090 kit are specifically formulated to resist swelling and degradation when exposed to Komatsu BIO HF-2 and HF-3 biodegradable hydraulic fluids, as well as standard KES 07.881 mineral oils. This bio-oil compatibility is essential for environmentally sensitive job sites.
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