In the process of overhauling an engine, though new main & connecting rod bearings are used, incorporating the worn ones for inspection can be highly informative of the heath of the engine. Major causes of bearing failure include impact, corrosion, severe loading or overloading of the engine, and foreign particles such as lack of lubrication and dirt and any of these must be rectified before the bearing is reinstalled to avoid a repeat. To examine the bearings unbolt them off from the engine block and arrange them in conjunction with the main bearing caps together with the connecting rods and rod caps on a clean surface which will enable one to match any defects on the bearings with the corresponding crankshaft journal. Particles may be picked up during the assembly process, through filters or breathers, or result from metal chips and abrasives which are left in components which have been reconditioned. The carrying particles, which are of a smaller size, may become lodged into the softer bearing material: larger particles may scratch or cut into the bearing and the shaft. Prevention can be achieved by regular cleaning of all the components and constant oil and filter replacement. Failure of lubrication may be due to high operating temperature, overloading, leakage of oil and blocked oil ways that may cause rubbing off bearing material from the backing or extrusion of the backing at very high temperature. Driving behavior also influences the bearing life; high cyclic operating speeds and low speeds result in high load and can eliminate the oil film, short trips can result in corrosion due to low heat. There are other forms of failures for example, tight bearing fit or dirt trapped behind the inserts.