U.M.R. Engines

BIG END - FLOGGED / SEIZED / PICKED UP

The most important factor in extended bearing life is the maintenance of good lubrication.

Oil starvation is the most common cause of bearing pick-up or seizure. Loss of oil allows metal to metal contact, which results in bearing damage. Running engines consistently at low oil levels will eventually cause severe bearing damage. If this metal to metal contact is maintained for long enough the bearing will eventually weld itself on to the shaft and complete seizure occurs.

A dry start is the most common cause of bearing seizure or damage in the early stages of the running in procedure. A dry start occurs when the oil pressure is not obtained prior to starting a new or rebuilt engine. At initial start up a new engine can have little or no oil at the engine bearings so it is critical that the engine is cranked with no compression (plugs or injectors removed) until oil pressure is registered at a gauge or light. After registration of the oil pressure have a short pause until the light reappears or gauge reads zero, then re-crank the engine to verify initial cranking oil pressure. Only now should engine go under compression and be started. If the vehicle is only fitted with an oil warning light a master gauge should be used to establish the oil pressure to ensure correct pressure is maintained when the oil is hot..

Insufficient clearance upon assembly will result in engine bearing damage and may lead to pick up or seizure. This would more likely to be the cause if only one bearing was damaged and the other bearings were in good condition. Insufficient clearance allows the same metal to metal contact as in oil starvation, resulting in a picked up or seized bearing.

Fatigued big end bearings have the appearance of pieces of the bearing material broken away in a random pattern. The cause "lugging" will be more noticeable in the upper rod bearings while the cause "over revving" more noticeable in the lower cap bearings. Engines that "idle" excessively can suffer the same symptoms as "overloading."

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