Quick answer
A useful hydraulic test records the exact excavator, operating settings and test conditions, then checks individual and combined functions after the machine is ready for normal work. If movement becomes slow or uneven, request a diagnosis tied to that machine before agreeing a repair allowance. A short video of an empty bucket moving does not establish pump condition.
Key takeaways
- Link every test video and measurement to one inventory ID and serial number.
- Have an experienced operator and inspector agree the test area, method and stopping conditions.
- Record warm-up, work mode, engine setting and attachment so results can be compared.
- Separate a visible symptom from the technician's diagnosis and repair quotation.
- Retest the affected functions after an agreed repair before accepting the machine.
1. Agree the test before the demonstration
Tell the inspector what work the excavator must perform. Digging, grading and running a hydraulic attachment ask different questions of the machine. Agree which functions can be demonstrated in the yard, which need suitable material or equipment, and who will operate it. A restricted yard test should be recorded with its limits.
Keep the inventory ID, product link, serial plate and attachment description on the inspection record. Ask for a continuous opening shot that connects the machine to its identification, followed by clearly labelled clips of each test. A playlist of unrelated close-ups makes it difficult to decide whether a fault, repair and retest concern the same unit.
2. Separate the stationary check from operating tests
Before operation, ask the inspector to identify visible leaks, damaged hoses, cylinder-rod damage and previous repairs. Photograph the location and surrounding components. Clean paint and a dry surface are observations; neither establishes the internal condition of a pump or valve.
Caterpillar's hydraulic inspection guidance calls for visual and noise checks using the machine's manual and appropriate shutdown precautions. Follow the exact excavator manual for isolation and inspection. Keep people clear of moving equipment; pressure measurements and leak investigation belong to qualified technicians. Do not touch a suspected pressurised leak or open a hot hydraulic system.
Sources for this section:[1]
3. Record comparable operation after warm-up
Ask the operator to prepare the machine for testing according to its manual. Record the displayed temperatures when available, the work mode, engine setting, attachment and test surface. Use the same settings when repeating a movement. A change in mode, load or operator technique can make two videos look different without identifying a mechanical cause.
Observe boom, arm, bucket, swing and travel individually, then the combinations needed for your work. Keep the camera far enough away to show the movement safely. Note hesitation, uneven response, drift, abnormal sound or a warning message and the precise conditions in which it appears. Do not assign a universal acceptable cycle time, pressure or warm-up duration to different models.
| Test record | What to retain | Buying decision it supports |
|---|---|---|
| Machine and setup | Inventory ID, attachment, mode and engine setting | Confirms that repeated results describe the same configuration |
| Individual functions | Labelled clips and any measured cycle times | Identifies the movement needing closer investigation |
| Combined operation | Task, material and operator observations | Shows whether the required work was actually demonstrated |
| Repeated warm operation | Conditions and any change in response | Defines what a technician must reproduce |
| Warnings and leaks | Exact code or location with photographs | Connects the repair request to a specific finding |
4. Ask for a diagnosis when a symptom appears
An excavator that slows during a demonstration needs investigation; a video alone cannot establish which component is responsible. Ask the technician to reproduce the symptom, record the relevant diagnostic results and explain the conclusion. If a seller proposes replacing the pump, request the evidence that supports that repair and the items included in the quotation.
Where oil sampling is part of the agreed scope, retain the sample identification and the laboratory's interpretation. Caterpillar describes fluid analysis as a condition-monitoring tool supported by expert interpretation. Ask when the oil was changed and what system was sampled. Use the report alongside the operating inspection, rather than treating one sample as a guarantee of remaining service life.
Sources for this section:[2]
5. Turn the finding into an acceptance condition
Write down the affected function, agreed repair, responsible party and retest method. For a hose replacement, retain the installed-part detail and the inspection result. For a larger component repair, ask for the workshop scope and the conditions under which the machine was retested. The phrase 'hydraulics repaired' leaves too much open.
Compare the purchase with and without that work using a written workshop quotation. Include parts availability and the time needed before your first job. If diagnosis is incomplete, keep that issue open in the buying decision instead of giving it a zero repair cost. The buyer and seller should agree acceptance before payment milestones that depend on it.
6. Send a focused inspection request
For a Plinton listing, send the inventory ID and product URL with the functions you need checked. State whether the machine will mainly dig or run a particular attachment. Ask which tests can be arranged, who will perform them and what records you will receive. The scope is agreed for the selected machine.
Keep the final test record with the quotation. It should allow you to identify the unit, understand what was demonstrated, locate each finding and see the result of any retest. That is a more useful basis for choosing a machine than comparing short promotional clips.
- Inventory ID and original product URL
- Intended work and required attachment
- Requested operating tests and test conditions
- Diagnostic or sampling scope where agreed
- Repair items and written retest criteria
Frequently asked questions
Does slow operation when hot prove that an excavator needs a new pump?
No. Record when the symptom occurs and ask a qualified technician to diagnose the exact machine. A pump replacement decision needs evidence from the relevant tests, not the appearance of one video.
Is a warm operating test the same as checking hoses while the machine is running?
No. The operator performs the agreed operating demonstration with people clear of the machine. Close inspection, pressure testing and servicing follow the manual and the technician's safety procedures.
References
- How to Inspect Your Cat Equipment Hydraulics ↗Caterpillar · Accessed 2026-09-12
- S·O·S Services Fluid Analysis ↗Caterpillar · Accessed 2026-09-12
Editorial standard: Updated 2026-09-12. This guide separates general process guidance from machine-specific facts. Confirm the current inventory ID, machine evidence, inspection scope, carrier quotation and destination requirements before making a transaction decision. Read our editorial and verification standard.