How do you check the hydraulics on a used wheeled excavator?

With the machine warm, check for leaks at cylinder glands, hose ends and the rotary joint, and look for weeping under the machine after it has stood. Oil that is milky or dark, or a tank that smells burnt, points to water or overheating.

Then test function: cycle the boom, arm and bucket through full stroke, listen for cavitation or chatter, and check that drift is small when a loaded bucket is held. Slow or uneven functions can mean pump wear, a sticking valve or a tired cylinder.