Confirm the temperature and operating point
Record oil temperature, motor housing temperature, inlet pressure, return pressure, speed and flow after a repeatable operating period. A surface reading without the operating condition is difficult to compare.
Check return and case pressure
Restricted return lines, undersized hoses, blocked filters or an incorrectly connected case drain can increase losses and seal load. Compare measured back pressure with the motor and circuit requirements.
Check speed, load and internal leakage
Operating beyond the intended speed or continuous torque raises heat generation. Increasing leakage can also reduce efficiency. Leakage assessment must be made at a known pressure, speed and oil temperature.
Review oil and cooling capacity
- Correct viscosity at operating temperature
- Oil cleanliness and filter condition
- Reservoir level, cooler condition and air flow
- Aeration, cavitation noise or unstable inlet supply
Stop the machine if temperature, noise or pressure indicates an unsafe condition. Diagnosis should be carried out by qualified hydraulic personnel.
This guide supports preliminary discussion. Final selection must be confirmed from the specific model data, hydraulic circuit, installation drawing and machine safety requirements.