| Parameter | Specification |
|---|---|
| COGENG Part Number | 991/20021 (99120021) |
| OEM Equivalent | JCB 991/20021, JCB 99120021 |
| Product Type | Hydraulic Cylinder Seal Kit |
| Application | Backhoe loader hydraulic cylinders |
| Kit Type | Complete overhaul seal kit |
| Compatible Models | JCB 3CX, 4CX, 5CX and related backhoe loader models |
| Brand | Part Number |
|---|---|
| COGENG | 991/20021, 99120021 |
| JCB | 991/20021, 99120021 |
| Interchange | 991/20022, 991/20023, 991/20024, 991/00145, 991/00147, 991/00012 |
| 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 | 350 bar (5,075 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 |
| NO | Number | Name | Qty |
| 556/60476 | Ram assembly tilt, fixed | 1 | |
| 1 | :332/D4842 | Kit - end cap assembly | 1 |
| 2 | :590/40127 | Rod piston | 1 |
| 2A | ::1207/0011 | Bush | 1 |
| 3 | :595/ 10027 | Head piston | 1 |
| 4 | :826/01182 | Dowel | 1 |
| 7 | :556/70476 | Cylinder | 1 |
| 7A | ::1207/0019 | Bush | 1 |
| 12 | :1450/0001 | Nipple Grease, Straight 1/8 BSP | 3 |
| 50 | :991/20021 | Kit-seal universal 70X40 | 1 |
Q: What JCB models use the 991/20021 hydraulic cylinder seal kit?
A: The 991/20021 is a hydraulic cylinder seal kit designed for specific JCB backhoe loader cylinders, commonly used in boom, dipper, or stabilizer applications depending on machine configuration and production year. Seal kit compatibility can vary by cylinder serial number. Always verify this part number against your machine's parts manual or the cylinder's original seal kit reference before ordering.
Q: What are the symptoms of failing hydraulic cylinder seals on a JCB backhoe?
A: Common symptoms include visible hydraulic oil leaking from the cylinder rod or gland area, decreased lifting or digging force, cylinder drift where the implement slowly lowers under load, jerky or erratic cylinder movement, and external oil contamination around the cylinder assembly. Early seal replacement helps prevent internal cylinder scoring and more costly repairs.
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