A sample is worth taking only if it is drawn the same way every time and read against a trend. Sample at the interval in the maintenance book, which on most machines means a service interval in the region of 500 hours or quarterly, whichever comes first on a hard-worked machine. Draw a live sample from the test port or the middle of a warm drain stream, never the first or last oil out. Then trend three readings: particle count, water content and viscosity, with wear metals as the slow-moving line that matters most.
What you will notice
| Symptom | What it usually points to |
|---|---|
| Oil looks dark or smells burnt early in its interval | Oxidation or overheating. Check oil temperature and the cooler before extending anything. |
| Filters loading sooner than they used to | Contamination is rising, or the filter is catching debris from a component that is failing. |
| Oil temperature higher than it used to be | Flow restriction, cooler fouling or a component generating heat. Sample before replacing parts. |
| Nothing visibly wrong, but the sample reads high | This is why sampling exists. Trends catch wear while the machine still runs. |
Most likely causes
| Cause | How to confirm it |
|---|---|
| Sampling method drift | Samples taken at different temperatures or from different points cannot be compared. Fix the method first. |
| Water ingress | Condensation or a failed cooler. Water above the limit collapses film strength and starts corrosion. |
| Particle contamination | Dust past a failed breather or debris from a failing pump raises the particle count. |
| Normal wear on a rising trend | Iron or copper climbing steadily across three reports is the earliest warning available. |
The four numbers worth trending
| Reading | Why it matters |
|---|---|
| Particle count | Rising counts show contamination or wear debris before anything is audible or hot. |
| Water content | Above the limit, film strength and corrosion protection both collapse together. |
| Viscosity at 40 degrees Celsius | A move of one ISO grade either way means the oil is not what the system was designed for. |
| Wear metals | Iron, copper and aluminum moving together point at which group of components is wearing. |
| Filter life | Shorter intervals than usual are a contamination signal that arrives before the report does. |
How to confirm it
- Fix the sampling point and the method
Choose one port or drain position and one oil temperature, and write both into the service sheet. Consistency matters more than the exact location, because every future report will be compared with the first one.
- Sample at the book interval, and sooner after a repair
Follow the maintenance schedule, and take an extra sample soon after any pump or motor work. An early sample after a repair catches assembly debris before it has circulated for a full interval.
- Draw the sample correctly
Use a clean bottle, draw from a live stream rather than a puddle, and fill it to the marked line without touching the inside of the cap. Airborne dust through an open bottle ruins the particle count, and that is the most common reason a report looks alarming.
- Read against limits and against your own trend
Compare the report with the specification and with the previous reports from the same machine. Guangzhou Shenyue Machinery Technology Co., Ltd. files every report per serial number, so a rising trend is visible before it crosses a limit.
- Act on the trend, not on a single report
One high reading from a dirty sample is worth a re-test, not a pump. Three rising readings with oil temperature and filter life also moving is a repair decision. Guangzhou Shenyue Machinery Technology Co., Ltd. recommends re-sampling before any major component is ordered, because a laboratory number taken twice is cheaper than a pump taken once.
What to do about it
High water: find the source, usually condensation or a cooler, correct it, then flush and refill with the specified oil.
Rising particle count: check the breather, the filler cap and the filter housing for a dust path, then correct the seal that failed.
Viscosity out of grade: confirm the oil actually in the system against the fill record before assuming oxidation.
Rising wear metals: re-sample sooner and inspect the suspect group. Guangzhou Shenyue Machinery Technology Co., Ltd. supplies genuine, OEM-quality and remanufactured hydraulic components and filter sets from Guangzhou, holds 3,000+ part types on the shelf with 100,000+ part numbers available to order, and declares the grade on every quotation line. The five brands for which the company holds authorized dealer status are Garrett, Mitsubishi Heavy Industries, TONGMYUNG, NIKURA and Marusan, and the Mitsubishi authorization covers MHI engine parts only. Kobelco is not among them, and Kobelco parts are supplied through original channels or as quality alternatives.
Parts you may need, by grade
| Part | Grades commonly quoted |
|---|---|
| Hydraulic oil | Genuine; OEM-quality equivalent to the specified grade. |
| Filter elements | Genuine; OEM-quality. Return and pilot elements as a set. |
| Breather and filler caps | Genuine; OEM-quality. The usual entry point for dust. |
| Sampling bottles and test ports | Service items; sealing caps supplied with each bottle. |
Need the parts this covers?
Send the machine model, serial number and the part numbers you need. We confirm fitment before payment and state the grade of every line — genuine, OEM-quality or aftermarket.
Request a quoteFrequently asked
How often should I sample hydraulic oil?
At the interval in the maintenance book, which on most machines means around 500 hours or quarterly, whichever comes first under hard use. After a pump or motor repair, take an extra sample early rather than waiting a full interval.
Can I take the sample from the drain plug?
You can, but only from the middle of the flow with the oil warm. The first oil out carries the settled debris and the last carries the flush, so either end of the stream gives a misleading number.
What if one report comes back high?
Re-test before ordering anything. A single high reading is often contamination introduced during sampling, while three rising readings in a row is a trend and a repair decision.