Excavator slow when hot: the usual suspects

"Works fine in the morning, gets slow in the afternoon" is a classic hydraulic complaint. Before replacing expensive parts, check in this order:

1. Hydraulic oil level and condition: low or aerated oil causes cavitation.
2. Oil cooler and radiator: blocked fins are the number one cause of overheating. Blow them out from the clean side.
3. Cooling fan: on hydraulically driven fans, check the fan speed and control solenoid.
4. Oil viscosity: wrong grade for the climate.
5. Pilot pressure and filters: a weak pilot supply slows all functions.
6. Main pump: worn pumps leak internally more as oil thins when hot. A flow and pressure test by a technician confirms this.
7. Relief valves set low or leaking.

Read more in our hydraulic contamination guide.

What turned out to be the cause on your machine?