At the request of the insurance company, I met with the insured at the service garage where the equipment was taken for examination and repair. I was presented with a small piece of foreign material that was discovered in the initial phase of the tear down of the engine. Once the oil had been drained and the oil pan removed, an unidentified fibrous material was completely covering the oil pickup screen (the intake for the oil pump). This could very well have caused the engine to starve for oil causing catastrophic damage to the crankshaft main bearings and ultimate failure of the engine.
The fibrous material was heavily impregnated with metallic particles and flakes which would later be identified as originating from the crankshaft and main bearings which were severely damaged. The lab results of the oil samples that were taken confirmed that these particles were of the same consistency as the metal surfaces of the main bearings and crankshaft. At first glance, this foreign material appeared to be similar to fine steel wool. Because steel wool is not something one normally finds inside an engine, the owner suspected that it had been introduced into the engine via the oil filler neck as an act of vandalism. The concern the owner felt was supported by the fact that the machine had been left unprotected at a job site the night before. Further inquiry would reveal that no other equipment left on the job site at that time exhibited any signs of vandalism or experienced any type of mechanical breakdown.
Inspection of the engines crankshaft and main bearings showed significant scoring and deterioration, consistent with oil starvation. Oil pump failure is often associated with this type of failure, however, similar damage could also occur due to improper maintenance, technician error, and improper fit or improper installation of the bearings themselves. A careful review of the maintenance log revealed documented regular preventive maintenance, but of more interest was the discovery that the engine had indeed undergone a recent complete overhaul.
This information would command close attention due to the potential for mistakes made during the rebuilding process that could also cause premature failure of the internal components. The fibrous material which had accumulated around the oil pick up was microscopically examined then directly compared to fine steel wool which was also examined and photographed in the same manner. The dissimilar fibers helped conclude that the foreign material was the remains of a disposable shop towel that had been inadvertently left in the engine at the time of the overhaul. Over a relatively short period of time the shop towel had deteriorated and due to the suction of the oil pump, accumulated around the oil pickup screen.
Oil flow was significantly reduced and lack of proper internal lubrication resulted in the failure of the crankshaft main bearings. Although not criminal, the cause of the failure was accidental and not due to lack of maintenance or neglect of the equipment by the owner/operator.
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