Excavator Cylinder Seal Kit Compatibility by Brand & Model
A leaking excavator cylinder is one of the most common and most fixable failures on any machine. Before you weld a rod or replace the whole cylinder, the right move is almost always a seal kit: a set of O-rings, rod seals, buffer rings, wear bands and a wiper that restores pressure for a fraction of the cost of a new cylinder. This guide shows how to match boom, arm and bucket hydraulic cylinder seal kits to your excavator brand and model, with the real part numbers we ship every week.
What a Hydraulic Cylinder Seal Kit Contains
Every excavator has three families of cylinders - the boom cylinder that lifts the stick, the arm (or stick) cylinder that curls the bucket, and the bucket cylinder that opens and closes the coupler. Each kit is sized to that cylinder bore and rod diameter. A complete kit typically includes the rod seal, a buffer (or anti-extrusion) ring, a piston seal, wear bands that centre the piston, a wiper seal that keeps dirt out, and the relevant O-rings and backup rings. The boom cylinder seal kit therefore differs from an arm cylinder seal kit and a bucket cylinder seal kit, even on the same machine.
How to Tell a Cylinder Needs a Seal Kit
1. Oil filmed on the rod or pooling at the cylinder base after the machine sits overnight.
2. Slow drift - the boom or arm sags under load because pressure bleeds past worn seals.
3. External scoring on the rod from a failed wiper letting grit in (polish light scores, replace if deep).
4. Foaming or overheating hydraulic oil from air drawn in through a breached rod seal.
5. Visible weep at the gland nut once the machine is warm and pressurised.
Match the Kit to the Cylinder, Not Just the Brand
Most buyers search by brand, but the safe match is brand plus model plus cylinder position. The same Komatsu PC200 family uses different bore and rod sizes on the boom versus the bucket cylinder, so a single part number rarely fits all three. Always read the cylinder nameplate for the bore, rod diameter and stroke, or send us the machine serial so we confirm the exact kit before you pay.
Real Part Numbers by Brand and Model
|
Brand |
Model example |
Cylinder |
Seal kit reference |
|
Kubota |
KX018-4 mini excavator |
Arm / Bucket |
RG158-67680 |
|
Bobcat |
331 / 331E / 334 / 430 |
Bucket |
7137935 |
|
Hitachi |
ZX200 / ZX240 series |
Boom / Arm / Bucket |
Confirm by serial |
|
Komatsu |
PC200-8 / PC210-8 |
Boom / Arm / Bucket |
Confirm by serial |
|
CAT |
320D / 336D |
Boom / Arm / Bucket |
Confirm by serial |
|
Volvo |
EC210B / EC240B |
Boom / Arm / Bucket |
Confirm by serial |
|
Doosan |
DH220 / DX225 |
Boom / Arm / Bucket |
Confirm by serial |
|
Hyundai |
R225-9 / R305 |
Boom / Arm / Bucket |
Confirm by serial |
Two of those rows link to live product pages we ship daily: the Kubota KX018-4 arm and bucket cylinder seal kit RG158-67680, and the Bobcat 331 / 331E / 334 / 430 bucket cylinder seal kit 7137935. For every other brand and model, use the cylinder seal kit category and we will match the bore and rod size from your serial number.
A 5-Step Fitment Checklist
6. Identify which cylinder leaks - boom, arm or bucket - and its position on the machine.
7. Photograph the cylinder nameplate: bore, rod diameter and any stamped kit number.
8. Note the machine brand, model and serial from the cab plate or data plate.
9. Send those details to us; we cross-check against the correct kit before shipping.
10. Confirm warranty and dispatch time, then fit the kit with a clean bench and new rod if scored.
New Seal Kit vs Rebuilt Cylinder
A seal kit restores pressure when the rod and barrel are sound - that is 80 percent of leaks and the cheapest fix. Choose a full cylinder rebuild or replacement only when the rod is bent, the barrel is scored beyond repair, or the chrome is pitted. For mini excavators like the Kubota KX018-4 the arm and bucket seal kit RG158-67680 is a field-fit job; for a Bobcat 331 the bucket seal kit 7137935 gets the coupler working the same day.
Frequently Asked Questions
Q: Do boom, arm and bucket cylinders use the same seal kit?
Usually no. Each cylinder has a different bore and rod diameter, so the kit is sized per position. On a Kubota KX018-4 the arm and bucket share kit RG158-67680, but on larger machines all three are separate kits - confirm by cylinder, not just by brand.
Q: How long does a cylinder seal kit last?
A quality kit on a clean rod lasts roughly as long as the original seals - often 2,000 to 4,000 operating hours. Life drops sharply if the wiper fails and grit scores the rod, so replace a weeping kit early and keep the rod clean. For a Bobcat 331 the bucket kit 7137935 is the common refresh item.
Q: Can I install a seal kit myself?
Yes, with a press, snap-ring pliers and a clean bench. Support the cylinder, release pressure, and replace every seal in the kit as a set - never only the leaking one. If the rod or barrel is damaged, send the cylinder to a specialist or buy a complete unit instead.
Get the Right Cylinder Seal Kit, Fast
Matching a cylinder seal kit should take minutes, not days. XC Machinery stocks boom, arm and bucket seal kits for Kubota, Bobcat, Hitachi, Komatsu, CAT, Volvo, Doosan and Hyundai excavators, with real part numbers such as RG158-67680 for the Kubota KX018-4 and 7137935 for Bobcat 331-series buckets. Message your brand, model and serial on WhatsApp at +86 18758866446, or request a quote, and we confirm fitment and lead time within 4 hours.
