What are the key parameters to evaluate when inspecting a used piece of construction equipment for potential hydraulic system problems before purchase?

When inspecting a used piece of construction equipment for potential hydraulic system problems before purchase, several key parameters should be evaluated. These parameters provide insight into the condition of the hydraulic system and can help identify potential issues that could lead to costly repairs. First, visually inspect all hydraulic components for leaks. Check hydraulic cylinders, hoses, fittings, pumps, valves, and the hydraulic reservoir for any signs of leakage. Leaks indicate worn seals, damaged components, or loose connections. Second, check the hydraulic fluid level and condition. The fluid level should be within the specified range in the reservoir. The fluid should be clear and free of contaminants. Cloudy or milky fluid indicates water contamination, while dark or burnt-smelling fluid indicates overheating or degradation. Third, operate all hydraulic functions and listen for unusual noises. Operate each hydraulic cylinder and motor through its full range of motion and listen for any unusual noises, such as whining, grinding, or squealing. These noises can indicate worn pumps, damaged cylinders, or restricted flow. Fourth, check the cylinder drift. With the engine running and the hydraulic system pressurized, extend a hydraulic cylinder and then shut off the engine. Observe whether the cylinder retracts or drifts over time. Excessive drift indicates internal leakage within the cylinder. Fifth, check the system pressure. Use a pressure gauge to measure the hydraulic system pressure at various points. Compare the readings to the manufacturer's specifications. Low pressure can indicate a worn pump, a leaking valve, or internal leakage in a cylinder. Sixth, check the hydraulic oil temperature. Operate the equipment for a period of time and then check the hydraulic oil temperature. Excessive temperature can indicate a restricted flow, a worn pump, or a malfunctioning cooler. For example, if a used excavator shows signs of hydraulic fluid leaks, slow cylinder operation, and excessive noise from the hydraulic pump, it likely has significant hydraulic system problems that will require costly repairs. Therefore, careful evaluation of these parameters can help assess the condition of the hydraulic system and make an informed decision about purchasing used equipment.