Hydraulic Systems in Excavators: How They Work and Why Maintenance Matters

Hydraulic systems are the muscle of your excavator. Without them, your boom, stick, and bucket wouldn’t move an inch. They’re what give your machine its digging force, lifting power, and precision control. And while the technology might seem complex, the principle is surprisingly simple: hydraulics use pressurised fluid to do heavy lifting.

In this deep-dive, we’ll explore:

• What makes up an excavator’s hydraulic system

• How the system works

• Common failure points

• Why maintenance is critical

• The role of OEM used parts in keeping hydraulics in top shape

1. The Heart of the Machine

If the engine is the heart that pumps energy, the hydraulic system is the circulatory system that delivers power to where it’s needed. It turns rotational energy from the engine into linear motion — the kind you see when the boom rises, the stick extends, or the bucket curls.

2. Core Components of an Excavator’s Hydraulic System

A hydraulic system has four primary parts:

1. Hydraulic Pump

   • Converts mechanical energy from the engine into hydraulic energy by pressurising oil.

2. Control Valves

   • Direct pressurised fluid to different actuators (boom, stick, bucket, travel motors).

3. Hydraulic Cylinders and Motors

   • Cylinders create linear motion (lifting, pushing).

   • Motors create rotary motion (swing, travel).

4. Hydraulic Fluid & Reservoir

   • Fluid transmits power, lubricates, and cools the system.

3. How It Works — The Flow of Power

1. Engine powers the hydraulic pump.

2. Pump pressurises the hydraulic fluid.

3. Control valves open and direct pressurised oil to the desired actuator.

4. Oil pushes against a piston inside a cylinder (or turns a motor).

5. Oil returns to the reservoir, ready to be pressurised again.

It’s a closed-loop system, meaning the same fluid keeps circulating.

4. Why Hydraulics Are So Effective

Hydraulic systems multiply force efficiently. A small piston moving a short distance can make a large piston move with great force. This is why an excavator can lift several tons with precision control — something mechanical linkages alone could never achieve.

5. Common Hydraulic System Failures

Despite their strength, hydraulic systems are not invincible. The most common issues include:

• LeaksWorn seals, cracked hoses, or damaged fittings let oil escape, reducing pressure.

• ContaminationDirt, metal particles, or water in the oil can wear out pumps and valves quickly.

• OverheatingCaused by excessive loads, blocked cooling systems, or low oil levels.

• Component WearHydraulic pumps, motors, and cylinders wear down over time.

• CavitationAir bubbles form in the fluid, damaging internal components.

6. The Domino Effect of Poor Hydraulic Maintenance

A small leak or contaminated oil might seem minor, but hydraulics operate under extreme pressure (often above 300 bar / 4,350 psi). That means small problems escalate fast.

Example:A leaking cylinder seal leads to pressure loss. This makes the pump work harder, which increases heat and wears out seals elsewhere. Eventually, the entire system suffers — and costs skyrocket.

7. Signs Your Hydraulic System Is in Trouble

• Sluggish boom or bucket movement

• Jerky or inconsistent motion

• Strange noises (whining, knocking)

• Visible oil leaks

• Overheating alerts

• Low hydraulic oil levels

8. How to Prevent Hydraulic Failures

1. Daily Checks

   • Inspect hoses, fittings, and cylinders for leaks.

   • Check oil level and colour.

2. Oil Sampling

   • Regularly analyse fluid to detect contamination early.

3. Filter Replacement

   • Replace filters on schedule to keep oil clean.

4. Cooling System Maintenance

   • Ensure oil coolers are free from debris.

5. Component Rebuilds

   • Rebuild pumps or cylinders before total failure.

9. Why OEM Used Hydraulic Parts Are a Smart Choice

Brand-new OEM hydraulic components can be costly. OEM used parts offer:

• Lower cost without compromising fitment and reliability.

• Immediate availability to reduce downtime.

• Genuine compatibility with your machine.

Vikfin inspects and tests every used part, meaning you can trust the quality.

10. Case Study: Cutting Downtime in Half

A KwaZulu-Natal contractor had a Komatsu PC300 with a failing travel motor. The OEM lead time for a new unit was 4 weeks. By sourcing a tested OEM used motor from Vikfin, they were back on site in 48 hours — saving them R180,000 in lost productivity.

11. The Cost of Ignoring Hydraulic Problems

If you continue running with low pressure or contaminated oil, you risk:

• Destroying pumps

• Warping valve spools

• Damaging cylinder rods

• Burning out motors

What could have been a R5,000 seal replacement can turn into a R150,000 full system overhaul.

12. Hydraulic Safety Considerations

Hydraulics are dangerous if mishandled:

• Never inspect leaks with your hands (oil injection injuries can be life-threatening).

• Always depressurise the system before repairs.

• Use the correct lifting and blocking equipment when working on heavy components.

13. Hydraulic System Upgrades

Some owners choose to improve their hydraulics with:

• High-efficiency pumps

• Better filtration systems

• Load-sensing technology

• Improved cooling solutions

These upgrades can extend service life and reduce fuel consumption.

14. Environmental Factors Affecting Hydraulics

• Dusty environments → more contamination risk

• Cold weather → oil thickens, slowing performance

• Hot climates → overheating risks rise

Matching oil viscosity to your operating environment is critical.

15. Operator Training

Even the most robust hydraulic system can be ruined by misuse:

• Avoiding abrupt, jerky movements

• Not overloading the boom

• Performing proper warm-up routines before heavy lifting

16. Hydraulic Oil: The Lifeblood

Choosing the right hydraulic oil:

• Meets OEM viscosity and additive requirements

• Resists oxidation

• Protects against wear

• Works in your temperature range

And remember — changing oil on schedule is just as important as using the right type.

17. Planning for Hydraulic Maintenance

Create a schedule that includes:

• Daily checks

• Weekly filter cleaning (or replacement if needed)

• Monthly oil sampling

• Annual pump and cylinder inspections

18. The Role of Vikfin in Hydraulic Repairs

We help clients by:

• Supplying tested OEM used hydraulic parts (pumps, cylinders, motors)

• Offering technical advice for proper installation

• Delivering quickly to minimise downtime

19. Hydraulic System Longevity Tips

• Keep oil clean

• Replace seals at the first sign of wear

• Use OEM or OEM-equivalent parts

• Train operators on proper use

• Stick to a maintenance plan

20. The Bottom Line

Hydraulics are your excavator’s powerhouse. With proper care, they can last thousands of hours without major repairs. Neglect them, and you’ll face downtime, massive repair bills, and possibly lost contracts.

Your excavator’s productivity depends on its hydraulics — treat them as a top priority.

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