Heat in a hydraulic system comes from work being converted to heat somewhere unintended. Track the energy path before changing the cooler.
Send a hydraulic component for review: Include the complete model code, quantity, destination and available photos or drawings.
Where the heat is generated
- Continuous relief-valve bypassing while the machine idles
- Internal leakage in pumps, valves and cylinders
- Flow throttled across controls at high pressure
- Insufficient cooling or airflow, blocked coolers and fans
- Wrong fluid viscosity raising friction losses
Measurement and diagnosis
- Record oil temperature at the reservoir, cooler inlet and outlet
- Check the relief valve setting and whether bypass is continuous
- Compare pump flow against specification to find internal wear
- Verify cooler airflow, fan direction and fin condition
- Test with a calibrated thermometer, not the dash gauge alone
Fixes and records
- Correct the cause before adding cooling capacity
- Confirm fluid grade and operating viscosity for the duty
- Record temperatures, pressures and the change made
- Re-test at full operating duty before closing the issue