Volvo Penta Abnormal Combustion or Mechanical Knock

Loud knocking or metallic banging noise from engine under load.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Severely worn connecting rod or main bearings, Injector nozzle dribbling causing detonation, Incorrect injection timing, Use of wrong fuel type

How to Fix / Troubleshooting

Safety: Severe knocking can precede catastrophic engine failure. Shut down immediately if noise is sudden and loud.

  • Check fuel: Confirm correct diesel fuel is being used and that no gasoline or contaminated fuel has been added.
  • Listen and localize: Use a mechanic's stethoscope to localize the knock (top end vs bottom end) with engine idling only if noise is mild.
  • Injector test: Have injectors tested and serviced if combustion knock is suspected.
  • Professional inspection: Strong mechanical knock requires immediate professional evaluation; engine teardown may be necessary.
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Repair Difficulty

Professional Required 5/5

Required Part

Connecting Rod Bearing Set
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