707-99-37230 Boom Cylinder Seal Kit for Komatsu PC128US-2

The 707-99-37230 Boom Cylinder Seal Kit is an aftermarket replacement sealing kit for selected Komatsu excavator boom hydraulic cylinders. It is commonly referenced for the Komatsu PC128US-2 and for compatible boom cylinder assemblies used on selected PC130-6 and PC138USLC-2 machines.

707-99-37230 Boom Cylinder Seal Kit Specifications

The listed rod and bore dimensions are catalog references for the 707-99-37230 application. Final compatibility must be confirmed against the actual boom cylinder and the supplied kit specification.

Compatible Komatsu Excavators and Cylinder Assemblies

The 707-99-37230 seal kit is listed for the following Komatsu boom hydraulic cylinder applications:

For PC128US-2 applications, parts references include machines from serial number 5001 onward. Other models and production versions must be checked individually. Cylinder assembly numbers are identification references, not interchangeable seal kit part numbers.

Typical Sealing Components

A boom cylinder repair kit for this application may include several types of sealing and support components, depending on the cylinder version and supplied kit configuration:

• Rod seals for hydraulic fluid retention around the piston rod.

• Buffer seals to assist with pressure control near the rod sealing area.

• Piston seals for separation of hydraulic pressure chambers.

• Dust wipers to limit entry of external contamination.

• O-rings and back-up rings for applicable static sealing locations.

• Wear rings or guide elements where specified by the cylinder design.

The exact number, dimensions, materials and arrangement of supplied components must be confirmed against the corresponding seal kit specification. Not every repair kit contains the same combination of seals.

Boom Cylinder Leakage and Repair Inspection

Boom cylinder seals may require inspection when hydraulic oil leakage, cylinder drift or abnormal boom movement is observed. These symptoms can have multiple causes, so the entire cylinder should be inspected before replacing the sealing components.

During repair, check the following:

• Piston rod condition, including scoring, corrosion and damage.

• Cylinder barrel wear and internal surface condition.

• Piston and rod seal grooves for wear or deformation.

• Cylinder head and guide surfaces.

• Correct installation orientation of each seal.

• Hydraulic oil cleanliness and possible contamination.

Seal installation should follow the applicable Komatsu cylinder service procedure. Damaged mechanical components should be repaired or replaced before fitting new seals.