score on flame face

Incorrect Overhaul

Investigation & Rectification


We recently received a Caterpillar 3412 from an offshore operator after they had a surprising discovery when removing a cylinder head.

The engine had been overhauled by another provider, and then run for a grand total of 11 hours.

But when the crew removed the cylinder heads to sort a problem on another 3412 engine, serious concerns were raised.

And once it arrived in our workshop, it was obvious to see why, with some big question marks over the standards of the previous overhaul, highlighted by the following:

  • Liner scoring, showing the liners should have been replaced, or there’s a more significant underlying issue that’s caused these issues after only 11 hours
  • Scoring on two cylinders

  • A piston which had fuel sat on top and no real carbon build-up, indicating the injector was not operating correctly
  • Piston looking damp and much cleaner than the rest.

  • The turbocharger air outlet hoses have delaminated and required replacement
  • A score mark was discovered on the flame face between combustion chambers
  • Some of the valve springs, valves and collets were then selected at random across the two heads for removal and inspection. Those removed were found to be in a poor unserviceable condition, and likely mirror the condition of the others
  • Debris was found lying in the sump – this raises concerns of potential damage to other parts of the engine

We could continue with further issues about the big end bearings, lack of antifreeze or inhibitor, bent fins and cracked rocker gear, but I think you get the picture!

During any overhaul, there will be a list of parts that should be replaced or inspected and a full report with measurement and inspection sheets to confirm best practice has been carried out.

For information on the steps, our engineers take during overhauls, click here.

Please feel free to get in touch for some impartial, specialist advice if you have any concerns about previous work or questions about upcoming scopes.

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