It is important to renew the main and connecting rod bearings while overhauling the engine, to keep the old bearings for evaluation of the state of the engine. Several features can cause bearing failure; inadequate lubrication, contaminants such as dirt, foreign particles, overload on the engine, and corrosion, among them all must be ascertained and rectified before reuniting the engine again to avoid future incidences. When examining the bearings, the bearings should be taken out from the engine components and arranged in their orientations on a clean surface for practical use comparing any defects observed with the crankshaft journal. These foreign particles can end up in the engine assembly remnants, filters or through the PCV system, are are often metallic in nature such as from machining processes or abrasive particles that were used to recondition items to be installed in the engine. These contaminants can become lodged into the bearing material, whereas the larger particles might produce scoring or gouging. Thus, to avoid such failures, all the parts have to be cleaned frequently, and the oil and filter have to be replaced. The causes of inadequate lubrication are heat, overloading, leakage, or blockage, and oil passages lead to the extreme extent where the bearing material is completely removed from its backing. Other behaviours also affect the bearing life span and include; sharp acceleration pressures at low speeds which cause high loads to squash out oil and; short journies that may cause corrosion due to inadequate heat. Also, some improper bearings installation may lead to oil starvation or the formation of high spots that lead to the failure of the bearings.