Hydraulic leaks are the most common reason an excavator comes into the shop — and seal kits are the fix. But ordering the wrong kit wastes a week. Here’s how to get the right seals the first time, whether it’s a boom cylinder, a travel motor, or a track adjuster.
Cylinder Seal Kits: Measure Twice
A cylinder kit must match bore diameter, rod diameter, and gland dimensions. The cylinder model number (stamped on the barrel, e.g., CAT 320D boom cylinder) is the fastest route — but verify against measurements, because cylinders get replaced with aftermarket units over a machine’s life. A complete kit includes the rod seal, piston seal, wiper, wear rings, and O-rings. Don’t forget the wear rings: if the old ones are scored, new seals alone will fail quickly.
Travel and Swing Motor Kits
Final drive (travel motor) leaks usually come from the duo-cone/floating seal between the hub and housing — not from the hydraulic motor section. Duo-cone seals are sold as matched metal-ring + O-ring sets and must be installed as a pair with the correct orientation. Swing motor kits follow the same pattern. Identify by the drive manufacturer’s number (e.g., Nabtesco, KYB) rather than the machine brand.
Track Adjuster (Grease Cylinder) Seals
A track that won’t hold tension is almost always the track adjuster seal. These are simple kits — typically one U-cup and an O-ring — but the sizes are model-specific. If the adjuster cylinder bore is scored, seals alone won’t hold; check the bore surface before ordering.
Installation Tips That Prevent Comebacks
- Cleanliness is everything — one grain of grit under a rod seal causes a leak path
- Use proper seal picks, never screwdrivers, on seal grooves
- Lubricate seals with clean hydraulic oil during assembly, not grease
- Replace wear rings and wipers with every reseal — they’re cheap insurance
- Torque the gland to spec; over-tightening deforms the rod seal
We stock cylinder seal kits, travel/swing motor kits, duo-cone seals, and track adjuster kits for all major excavator brands. Browse seal kits or send your cylinder or drive numbers and we’ll match the kit.