Stop and call the office (513-375-4814) if:
- Pump is hot to the touch, smoking, or the noise is getting rapidly worse
- Reservoir level is below the pump suction or foaming over
- Relief valve setting would have to be changed to stop the noise (customer engineering decides relief settings)
Before you start
- Listen first with the unit running from a safe position; record a phone video with audio at idle and under load.
- Note oil level, oil temperature, and whether the noise changes with load, with temperature, or with a valve shifting.
Symptom → cause → check
| Symptom | Likely causes | Check / do |
|---|---|---|
| Steady high-pitched whine/scream, worse cold or at high flow | Cavitation — starved suction: clogged suction strainer, collapsed suction hose, oil too cold/thick, low level | Check level and temperature; inspect suction strainer and hose; confirm suction valve fully open. |
| Rattling/gravel sound, milky or foamy oil | Aeration — air drawn in at a suction leak or return line above oil level | Look for foam; check suction fittings and shaft seal; confirm return lines discharge below oil level. |
| Pure tone (whistle/squeal) that comes and goes, often at idle | Relief or bypass valve 'singing' — flow passing through a valve near its cracking point | Note when it occurs vs. machine state; compare with valve shifting. Report — do not adjust relief settings. |
| Knocking that follows motor speed | Coupling wear or misalignment, pump bearing failure | LOTO, inspect coupling insert and alignment; check for pump shaft play. |
Close-out
- Attach the audio/video to the field log with the machine state for each clip.
- Write which cause you ruled out and how (e.g., 'level OK, strainer clean, no foam').
- If it's valve-related, the recommendation goes to the customer's maintenance lead through the office.
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