Introduction

The Rexroth A4VSO series axial piston pump is widely used in excavators, construction machinery, and industrial hydraulic systems. While highly reliable, prolonged operation under heavy load may cause issues such as pressure instability, noise, or leakage.
This guide summarizes the five most common A4VSO failures, their root causes, and how the right spare parts can extend service life and reduce downtime.

1. Noise and Vibration

• Symptoms: Abnormal knocking or vibration during operation

• Root Causes: Worn piston shoes, cylinder block scuffing, or improper oil viscosity

• Solution: Replace piston shoes and cylinder block as a set. Check swash plate wear.

2. Pressure Instability

• Symptoms: Output pressure fluctuates, causing actuator jerks

• Root Causes: Worn valve plate, leakage in control piston, or spring fatigue

• Solution: Replace valve plate and inspect control components. Use recommended hydraulic oil.

3. Internal Leakage

• Symptoms: Reduced flow rate, system overheating

• Root Causes: Damaged sealing rings, scoring on cylinder block bores

• Solution: Replace sealing kits and cylinder block; inspect drive shaft.

4. Overheating

• Symptoms: Oil temperature rises quickly under moderate load

• Root Causes: Excessive friction, contaminated oil, clogged filter

• Solution: Flush system, replace filter, and renew piston/cylinder kit.

5. Shaft Seal Failure

• Symptoms: Oil leakage from pump front

• Root Causes: Excessive shaft wear, improper installation, high case pressure

• Solution: Replace shaft and front seal; check case drain routing.

Troubleshooting Table

Recommended Spare Parts

• Cylinder block

• Valve plate

• Piston shoe set

• Retainer plate

• Drive shaft

• Seal kit

Case Example

A mining contractor in South America upgraded their A4VSO71 pump using Halies replacement parts. The overhaul interval was extended from six months to twelve months, significantly reducing downtime and operating costs.

Conclusion

By understanding common Rexroth A4VSO failures and replacing the right components in time, operators can ensure stable hydraulic performance and reduce unplanned maintenance.

Contact Halies Today

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