Many CAT machines drive the cooling fan with a hydraulic motor. The ECM or a fan controller changes speed with temperature. If the motor leaks or the control valve sticks, the fan cannot pull enough air when the machine is loaded.
What to look for
- Temperature climbs in heavy work and drops at idle
- Oil wetness around the fan drive
- A fan that turns slowly or not at all
- Noise from the motor bearing
Before you replace the motor, check the hydraulic supply, the speed sensor, and whether the radiator and coolers are packed with dust. A new motor cannot cool an engine if the cores are blocked.
Give the machine serial when you enquire. Fan motors are not shared across every excavator in a series.