Motor noisy or vibrating (bearing / mechanical)
The motor runs but is noisy, rough, or vibrating — grinding, rumbling, or whining noises that point to bearings or mechanical trouble.
Safety first
Severe vibration can loosen mountings and fasteners. Keep clear of couplings and shafts. Isolate before touching the shaft or bearings.
Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.
Full detail — causes, the why, and common mistakes.
Likely causes
Ranked from most to least likely.
- 1
Worn or failing bearings
Most likelyDry, worn, or damaged bearings rumble, grind, or whine and add vibration.
- 2
Misalignment or coupling fault
#2A misaligned coupling or worn drive coupling causes vibration and noise.
- 3
Loose mounting / imbalance
#3Loose feet or an unbalanced fan/load create vibration that grows with speed.
- 4
Electrical noise (supply imbalance)
Least likelySome hums/vibration come from electrical imbalance rather than mechanics.
Reports are saved on this device to reflect what you actually find.
Testing sequence
Work through one test at a time. Expected reading and what each result means.
Isolate, lock off, uncouple if possible, and turn the shaft by hand listening/feeling for roughness.
Smooth, quiet rotation with no notchiness.
Bearings feel fine — check alignment, mounting, and supply.
Rough/notchy bearings are the likely cause — plan a bearing replacement.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Motor noisy/vibrating
→ step 2 - 2decision
Do the bearings feel rough turning the shaft by hand?
Yes→ step 3No→ step 4 - 3result
Rough bearings — plan bearing replacement.
- 4decision
Are coupling/alignment/mounting all good?
Yes→ step 5No→ step 6 - 5result
Check supply balance for electrical-origin noise.
- 6result
Misalignment or loose mounting — correct it.
Common mistakes apprentices make
- Running a noisy bearing to failure instead of replacing it early.
- Blaming the motor when the coupling or alignment is the issue.
- Not checking the mounting bolts are tight.
- Ignoring supply imbalance as a noise source.
When to stop & escalate
Bearing replacement, alignment, and balancing are typically mechanical tasks — coordinate with the mechanical team. Catch bearing noise early to avoid a seized-motor failure.
If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.
Related faults
Motor running hot / overheating
The motor runs but gets excessively hot — too hot to touch, smell of hot insulation, or thermal protection cutting in after a while.
Motor overload keeps tripping
The thermal/electronic overload trips repeatedly, either on start or after the motor has run for a while. Resetting only buys you a short run before it trips again.
Three-phase equipment single-phasing (lost a phase)
Three-phase equipment is misbehaving — motors humming, struggling, overheating, or tripping — because one phase has been lost somewhere between the supply and the load.