Hydraulic System of Excavator: Common Issues and Solutions

1. Slow Operation or Weak Power

Possible Causes & Fixes

Cause	Diagnosis	Solution
Low Hydraulic Oil	Check sight glass/dipstick	Top up to recommended level
Clogged Filters	Inspect suction/return filters	Replace filters, flush system
Worn Hydraulic Pump	Test pressure (below 2500 PSI?)	Rebuild or replace pump
Sticking Relief Valve	Listen for constant “whining”	Clean/adjust valve or replace
Air in System	Foamy oil in reservoir	Bleed air, check suction lines

Pro Tip: Always check pilot pressure first (should be 350-500 PSI) before major disassembly.

2. Hydraulic Oil Overheating (Beyond Ambient Temp)

Troubleshooting Overheating

Normal Operating Temp:

• 50-70°C (122-158°F) – Ideal
• Above 80°C (176°F) – Critical

Common Culprits:

• Blocked Oil Cooler (Clean fins with compressed air)
• Wrong Oil Viscosity (Use ISO VG 46 for most climates)
• Continuous Overloading (Avoid max pressure >30 mins)
• Failing Pump (Internal leakage → energy loss as heat)

Emergency Cool-Down:

1. Stop operation immediately
2. Run at idle 5 mins to dissipate heat
3. Check cooler fan operation

3. Hydraulic Leaks at Connection Points

Leak Identification & Repair

Leak Location	Likely Cause	Fix
Hose Fittings	Worn O-rings/seals	Replace seals, torque to spec
Cylinder Rods	Damaged rod seals	Rebuild cylinder (new seals)
Valve Blocks	Loose bolts	Re-torque (use thread locker)
Pump Housing	Cracked casing	Replace pump immediately

Temporary Fix:
Hydraulic sealant tape (for threaded connections only) – not for long-term use!

4. Unusual Noises During Operation

Sound Diagnosis Guide

Noise Type	Probable Issue	Action
Whining	Cavitation (low oil/blocked suction)	Check oil level, clean strainer
Knocking	Air in system	Bleed air, inspect suction lines
Grinding	Pump/motor bearing failure	Replace bearings or unit
Banging	Shock waves (quick valve shifts)	Adjust damping valves

Critical Check:
Inspect hydraulic oil for metal particles – indicates internal damage.

5. Unresponsive/Jerky Cylinder Movements

Step-by-Step Troubleshooting

1. Check Pilot Pressure
   • Should be 350-500 PSI
   • Low pressure? Inspect pilot pump/filter
2. Test Control Valves
   • Sticking spools? Clean with hydraulic cleaner
   • Worn valves? Replace complete block
3. Inspect Cylinders
   • Internal bypassing? Rebuild with new seals
   • Bent rods? Replace cylinder
4. Evaluate Hydraulic Oil
   • Contaminated? Full system flush required
   • Wrong type? Drain and refill with OEM-spec oil

Quick Fix for Jerky Motion:
Cycle cylinders 10-15 times fully to purge air.

Preventative Maintenance Schedule

Interval	Key Tasks
Daily	Check oil level, inspect for leaks
Weekly	Clean oil cooler, check hoses
250 hrs	Change return filters, test pressure
1,000 hrs	Full oil/filter change, flush if needed
2,000 hrs	Pump/motor performance test

Invest in:

• Laser thermometer (monitor component temps)
• Pressure test kit (check pump/valve performance)

When to Call a Pro:

• If problems persist after basic troubleshooting
• For major component rebuilds (pumps, control valves)

Proper hydraulic maintenance can double your excavator’s lifespan – never ignore early warning signs!