How to Inspect the Hydraulic System Before Buying a Used Excavator

Why the hydraulic system deserves close attention

The hydraulic system powers the boom, stick, bucket, swing and travel functions. A machine may look clean in photographs while still having weak pumps, leaking cylinders or contaminated oil. The purpose of a pre-purchase inspection is not to prove that every component is new. It is to identify visible defects, compare operating performance and decide whether further pressure testing is needed before the price is agreed.

1. Start with the machine cold

Ask the seller not to warm up the excavator before the inspection. A cold start can reveal slow response, unusual pump noise and leaks that may be less obvious after the oil becomes warm.

• Confirm the machine identification and recorded hours before testing.
• Check the hydraulic oil level and look for foam, cloudiness, water or burnt odour.
• Inspect the pump area, control valve area, hose connections and cylinder seals.
• Look for fresh paint or recently cleaned areas that may hide an active leak.
• Never use a hand to search for a pressurised hydraulic leak.

2. Inspect hoses, fittings and cylinder rods

Follow every visible hose and hard line. Look for wet fittings, cracked outer covers, rubbing marks, damaged clamps and repairs that do not match the surrounding components. A film of oil mixed with dirt around a seal can be an early sign of leakage.

Cylinder rods should be straight and free from deep scoring, rust or impact damage. Check the boom, stick and bucket cylinders individually. Also inspect pins and bushings because excessive linkage play can feel like a hydraulic problem during operation.

3. Listen to the pump and test every function

Operate the machine in a safe, open area and follow the operating manual. Listen for persistent whining, grinding or cavitation noises. Test boom raise and lower, stick in and out, bucket curl, swing in both directions and forward and reverse travel.

The functions should respond predictably without severe hesitation, pulsing or a major difference between left and right travel. Combine two functions to see whether the machine remains controllable under a normal working load. Do not judge performance from one fast movement while the machine is unloaded.

4. Bring the oil to normal operating temperature

Cold oil can temporarily mask internal leakage. After the excavator reaches the temperature specified for testing, repeat the main functions and compare response speed. Check again for leaks around hoses, pump connections and cylinder seals.

A technician can perform timed cycle tests and compare the results with service data for the exact model and serial number. Generic internet figures should not replace the correct service specification.

5. Check cylinder drift

Cylinder drift can indicate internal leakage in a cylinder or control valve. Position the attachment exactly as required by the service instructions, measure the cylinder position, wait for the specified time and measure again. The ground must be level and the work area must be clear.

Do not invent an acceptable drift limit. The correct limit depends on the model, linkage position, oil temperature and test procedure. If movement appears excessive, request a model-specific test by a qualified technician.

6. Request evidence before agreeing the price

• Cold-start video with the dashboard and hour meter visible.
• Walkaround video showing the pump compartment, hoses and cylinders.
• Video of all digging, swing and travel functions at working temperature.
• Close photographs of any leak, damaged hose or scored cylinder rod.
• Diagnostic codes, service history and oil-analysis results when available.
• Pressure and cycle-time test results if performance is in doubt.

Warning signs that justify a specialist inspection

Stop and investigate further if the machine has persistent pump noise, very slow functions after warming, repeated hose failures, metal particles in the oil, heavily scored rods, active high-pressure leaks or unexplained overheating. These signs do not automatically make the excavator unusable, but the likely repair scope should be identified and reflected in the written quotation.

Final buying rule

Inspect the exact machine, not only the model. Record its serial number, configuration, attachments and visible defects. A clean inspection result reduces uncertainty, while a documented defect gives the buyer a basis for repair planning and price negotiation. Always use the operation and maintenance manual and a qualified technician for pressure tests or work near pressurised components.