Applicable Systems
EC220 Excavator
Symptoms
The hydraulic oil temperature has exceeded 90C (194F). The system derates hydraulic functions to prevent oil breakdown and seal damage.
Possible Causes
- Hydraulic oil cooler fins blocked by dust and debris
- Hydraulic oil level low, reducing the thermal mass and cooling capacity
- Continuous operation at maximum pressure generating excessive heat
- Cooling fan motor or circuit failed, reducing airflow across the cooler
Troubleshooting Steps
- Step 1: Inspect the hydraulic oil cooler for external blockage
Clean with low-pressure water or compressed air from the fan side - Step 2: Check the hydraulic oil level and top up if low
Use ISO VG 68 anti-wear hydraulic oil - Step 3: Verify the cooling fan operation by observing rotation during operation
If the fan is not running, check the fan motor and its control solenoid - Step 4: Allow the system to cool by idling the engine and cycling hydraulic functions lightly
Oil temperature should drop below 80C within 10 minutes of light operation
How to Reset
Reset: The alarm clears automatically once the hydraulic oil temperature drops below 80C.
Common Replacement Parts
- Hydraulic oil cooler: Air-to-oil, bar-and-plate type (Match to machine model)
- Cooling fan motor: Hydraulic gear motor, 0.5-2 kW equivalent (Check fan blade condition)
- Hydraulic oil: ISO VG 68 anti-wear (Full system capacity per manual)
Frequently Asked Questions
- Q: What is the maximum hydraulic oil temperature?
Most systems alarm at 90-95C and shut down at 100C. Prolonged operation above 85C significantly shortens oil and seal life.
- Q: How do I prevent overheating?
Keep the cooler clean, maintain correct oil level, and avoid continuous maximum-pressure operation. Consider an auxiliary cooler for hot climates.
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Source: OEM Service Manual
Category: Heavy Equipment
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