Hitachi ZX350K-3G Boom Cylinder Seal Kit 4686321 | 4686333

Part 4686321: boom cylinder seal kit, listed for the Hitachi ZX350K-3G excavator. Cross-reference numbers listed with it: 4686333.

Three checks before ordering:

1. Your machine is a Hitachi ZX350K-3G.
2. The part number of your cylinder lines up with 4686321.
3. The serial number agrees, if the part number is unclear.

• Item no.: 4686321
• Model: Hitachi ZX350K-3G
• Position: Boom cylinder
• Related numbers: 4686333
• Compounds: PU, Viton and NBR rubber

The boom cylinder raises and lowers the boom, so its seals work against the weight of the whole front end. Oil weeping at the rod, a cylinder that creeps down under load and digging that feels weak are the usual reasons a cylinder gets resealed. The compounds are polyurethane (PU), Viton and NBR. PU copes with pressure spikes, Viton with heat, and NBR is the usual oil-resistant rubber.