While overhauling an engine, it is mandatory to use new bearings for the main and connecting rods but it is advisable to keep the worn out bearings to with you this is because they will tell a lot about the engine. Designated bearing failure can be attributed to lack of lubrication, dirt contamination, overloading and corrosion and besides requiring an overhaul, these must be fixed to prevent reoccurrence when rebuying the engine. When inspecting the bearings they must be taken off the engine parts and placed at the locations they occupied to relate the defects to the crankshaft journal. Contaminants such as tramp oil, metal particles, asphalts, anti-freeze, water condensation, assembly residues from filters can contaminate the engine and metal particles resulting from machining or lack of proper cleaning can get into the bearing material, therefore causing harm. Such failures can be prevented by frequent cleaning of all parts and also change of oil and filters. Reduction of lubrication is got due to such aspects like heat, overload, leakage of oil, blocked passages and this may cause the bearing material to extrude out from its backing and overheat. Conduction also speaks about the driving habits which affects the bearing span; for example, low speed with full throtle develops high loads which tend to squeeze out the oil film or short trip journey that causes corrosion owing to absence of heat. Also, bearings may be damaged due to improper installation, where oil may be starved or there may be high spots that bring about the failure.