Applicable Systems
EC220 Excavator
Symptoms
The hydraulic system pressure has dropped below the minimum operating threshold of 200 bar (2900 psi). The boom and bucket movements become sluggish.
Possible Causes
- Hydraulic oil level low due to a leak in the cylinder seals or hoses
- Main hydraulic pump worn, delivering reduced flow and pressure
- Relief valve stuck open or set too low, bypassing oil to tank
- Clogged suction filter restricting pump inlet flow
Troubleshooting Steps
- Step 1: Check the hydraulic oil level in the sight glass and inspect for external leaks
Top up with ISO VG 68 hydraulic oil if level is below the MIN line - Step 2: Connect a pressure gauge to the main pump test port and measure delivery pressure
Compare the reading to the manual specification; if low, investigate the pump and relief valve - Step 3: Inspect the hydraulic suction filter for clogging
Replace if the differential pressure indicator shows red - Step 4: If pressure is still low, check the main pump output flow using a flow meter
If flow is below specification at rated speed, the pump needs overhaul or replacement
How to Reset
Reset: The fault clears automatically once hydraulic pressure is restored above the minimum threshold.
Common Replacement Parts
- Hydraulic suction filter: 10 micron, spin-on type (Replace every 1000 hours)
- Hydraulic oil: ISO VG 68, anti-wear type (Capacity: approximately 120-200L depending on model)
- Main relief valve: Set to 350 bar (Do not adjust without a calibrated pressure gauge)
Frequently Asked Questions
- Q: What hydraulic oil should I use?
Use ISO VG 68 anti-wear hydraulic oil meeting ISO 11158 HV specs. In cold climates, use ISO VG 46.
- Q: How often should hydraulic oil be changed?
Every 2000-4000 hours depending on oil analysis results. Sample the oil annually.
- Q: What causes main pump failure?
Contamination is the leading cause. A clogged suction filter starves the pump, causing cavitation and rapid wear.
Source: OEM Service Manual
Category: Heavy Equipment