CAT E70B Boom Cylinder Seal Kit 0995310 Caterpillar Excavator Repair Kit

0995310 Boom Cylinder Seal Kit O-Ring Rebuild Repair Gasket Component Set Fits Caterpillar CAT E70B Heavy Excavator Digger Lift Main Boom Hydraulic Replacement Parts

The boom cylinder is the hardest-working hydraulic component on the CAT E70B — it lifts, holds, and lowers the entire boom assembly through every single digging cycle, often supporting the combined weight of the boom, arm, bucket, and payload at full extension. Unlike the arm or bucket cylinders, the boom cylinder spends significant time under sustained static load (holding position while the operator digs or dumps), which puts unique stress on the seal package: rod seals must resist creep under constant pressure, not just dynamic wear from movement.

This 0995310 seal kit is manufactured to match CAT’s original boom cylinder tolerances, addressing the two failure modes most common on E70B boom cylinders after extended service: rod seal hardening from prolonged heat exposure near the engine bay, and piston seal wear from the repetitive full-stroke cycling typical of trenching and grading work.

Common Signs Your E70B Boom Cylinder Needs This Seal Kit

• Boom slowly sinks on its own when the machine is left idling
• Oil residue building up along the boom cylinder rod, especially after a full workday
• Noticeably reduced lift speed or lifting power compared to when the machine was new
• Jerky or hesitant boom movement when first raising it from a full-down position
• Visible oil pooling near the base of the boom cylinder mount

A slowly sinking boom is the most telling sign of internal bypass — oil is passing through worn seals inside the cylinder rather than leaking externally, so you may not see a drip even though the seal has failed.

Technical Specifications

• Compatible Brand: CAT (Caterpillar)
• Machine Model: E70B
• Application: Boom Cylinder Repair
• Part Number (SKU): 0995310
• OEM Reference Number: 0855096 / 0995310
• Seal Materials: Polyurethane (PU) piston and rod seals, high-grade NBR O-rings and back-ups
• Recommended For: General excavation, trenching, grading, and site development work

Why Choose Our Heavy-Duty CAT Seal Kits?

1. Premium Grade Materials
Manufactured using advanced Polyurethane (PU) and high-grade NBR rubber compounds, built to withstand extreme hydraulic pressures and resist long-term wear — including the sustained static loading unique to boom cylinder applications.

2. Exact Match Fitment
Precision-engineered dimensions guarantee a seamless, zero-leak drop-in replacement, significantly minimizing your machine’s downtime.

3. Built for Harsh Environments
Provides reliable defense against dust, slurry, moisture, and hydraulic oil breakdown — even in the heat-soaked environment near the E70B’s engine compartment, where boom cylinder seals are especially prone to premature hardening.

What’s Included in the Kit

• Piston seal (PU)
• Rod seal (PU)
• Dust wiper
• O-rings (NBR)
• Back-up rings
• Buffer ring (if applicable to cylinder design)

Note: Please confirm your machine’s serial number range when ordering, as CAT occasionally revised boom cylinder specifications across E70B production years.

Installation Tips

• Support the boom securely with blocking or a crane before disconnecting the cylinder — never rely on hydraulic pressure alone to hold the boom while working on it
• Check the rod surface for pitting near the seal contact area before installing new seals; a pitted rod will quickly damage new seals
• Coat all seals lightly with clean hydraulic oil before installation to ease assembly and prevent nicking
• Cycle the boom slowly through a full range of motion after reassembly to purge trapped air before returning to normal operation

⚠️ Important Fitment Note

To ensure a 100% accurate match, please verify your specific machine model, cylinder part number, or equipment serial number prior to purchasing. If you are unsure, feel free to contact our team for expert verification.

Frequently Asked Questions

Q: Is this kit for the boom cylinder, arm cylinder, or bucket cylinder?
A: This kit (0995310) is specifically for the boom cylinder — the cylinder that raises and lowers the main boom arm. It is not compatible with the E70B’s stick/arm or bucket cylinders, which use different seal dimensions.

Q: My boom drifts down overnight — will this fix it?
A: Boom drift is typically caused by worn piston or rod seals allowing internal oil bypass. This is exactly the failure mode this kit is designed to correct, assuming the cylinder barrel and rod surfaces are not themselves damaged.

Q: Can I replace these seals without removing the entire cylinder?
A: No — the cylinder must be removed from the machine and the rod withdrawn from the barrel to access and replace the internal seals safely.