1. The oil level in the oil separator barrel is too low. Add oil and check for leaks.
2. The oil cooler is too dirty or blocked. Clean the cooler core fins.
3. The fan belt is loose or damaged. Adjust the tensioner or replace the belt.
4. The thermal element of the temperature control valve fails. Replace the thermal element.
5. The oil pipe from the temperature control valve to the machine head is blocked. Clear the oil pipe.
6. The main oil inlet joint of the machine head is clogged. Clear the joint.
7. The oil filter is clogged, replace the filter element.
8. The secondary oil return pipe is blocked. Clean the filter and orifice of the oil return pipe.
9. Hot air refluxes. Move the machine and change direction to avoid reflux.
10. The ambient temperature is too high. Improve the ventilation environment.