707-99-58080 Boom Cylinder Seal Kit for Komatsu PC300-7 / PC300LC-7 Excavators
707-99-58080 is an aftermarket boom cylinder seal kit for the Komatsu PC300-7 and PC300LC-7 excavators, with extended coverage across the PC300/PC340/PC350 series per independent catalogs. It is a replacement for the Komatsu 707-99-58080 kit — it is not a genuine Komatsu OEM part.
Per TornadoParts, the kit matches a 100 mm rod × 140 mm bore boom cylinder and services OEM cylinder assemblies 707-01-0A430, 707-01-0A431, 707-01-0C580 and 707-01-0C581. Typical contents: press-in wiper, U-seal rod seal with buffer, and a 4-piece capped T-seal piston seal set. Confirm the exact component list with our sales team at [email protected].
Serial ranges per model are published in aftermarket catalogs — check the fitment table and verify your machine’s S/N before ordering. No pressure, temperature or service-life ratings are claimed; request the material data sheet with your order.
Verified Specs
| Parameter | Value / Verification |
| Part Number | 707-99-58080 — TornadoParts, ReliableAftermarketParts, YearnParts, eBay |
| Brand / Machine | Komatsu PC300-7 / PC300LC-7 (+ related series) — Multiple suppliers |
| Cylinder Application | Boom cylinder — Multiple suppliers |
| Rod Diameter | 100 mm — TornadoParts |
| Bore Diameter | 140 mm — TornadoParts |
| OEM Cylinder Assemblies | 707-01-0A430 / 0A431 / 0C580 / 0C581 — TornadoParts |
| Condition | New, aftermarket replacement — Multiple suppliers |
Confirmed / Reference Fitment
•Confirmed (≥2 sources): PC300-7 (TornadoParts, ReliableAftermarketParts, YearnParts, eBay, Amazon); PC300LC-7 (TornadoParts, ReliableAftermarketParts, eBay).
•Reference (single source, TornadoParts): PC300HD-7E0 / -7L / -8, PC300LC-7E0 / -7L / -8, PC300LL-7E0 / -7L, PC308USLC-3 (also ReliableAftermarketParts), PC340LC-7K, PC340NLC-7K, PC350LC-8.
Fitment Table (TornadoParts serial data)
| Model | Application / S/N From |
| PC300-7 | Boom / J20001-UP |
| PC300LC-7 | Boom / 40001-46350; 46351-UP |
| PC300HD-7E0 | Boom / A86001-UP |
| PC300HD-7L | Boom / A85001-UP |
| PC308USLC-3 | Boom / 20001-UP |
| PC340LC-7K / PC340NLC-7K | Boom / K40001-UP |
| PC350LC-8 | Boom / A10001-UP; B10001-UP |
Fitment Checklist
1.Machine model: confirm the full designation (e.g. PC300-7, PC300LC-7, PC308USLC-3).
2.Cylinder position: Boom.
3.Look for OEM cylinder P/N 707-01-0A430 / 0A431 / 0C580 / 0C581 on the cylinder.
4.Check your machine S/N against the ranges above.
5.Measure rod ≈ 100 mm, bore ≈ 140 mm.
When to Inspect / Replace
•Oil film or drips at the boom cylinder gland.
•Boom drift or slow lifting under load.
•Scored rod surface or contaminated oil.
On large excavators, also verify the relief/holding valve settings and rod straightness before resealing.
Wholesale & MOQ
Factory-direct supply for distributors, repair shops and fleet operators. Wholesale MOQ: 5 kits. Email [email protected] with your quantity, shipping port and destination for a same-day quote. Custom packaging and private labeling available.
FAQ
Is this a genuine Komatsu OEM kit? — No. This is a new aftermarket replacement for the Komatsu 707-99-58080 boom cylinder seal kit. The previous page text said “genuine OEM” — that was incorrect and has been removed.
Which machines does it fit? — Confirmed for PC300-7 and PC300LC-7; aftermarket catalogs also list PC300HD/LC/LL variants, PC308USLC-3, PC340LC/NLC-7K and PC350LC-8 — check the S/N ranges and your cylinder P/N (707-01-0A430 / 0A431 / 0C580 / 0C581).
What are the dimensions? — 100 mm rod × 140 mm bore per TornadoParts. Measure your cylinder to confirm before ordering.
Komatsu PC300-7 seal kit
707-99-58080
Komatsu boom cylinder seal kit
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