In the course of an overhaul, the main and connecting-rod bearings, on the one hand, should be renewed, while retaining the old ones on the same engines, on the other hand, for examination. Some of these problems may include improper lubrication, dust deposits, overloading of the engine, and cases of corrosion and all these must be attended to before reassembly is done to avoid repetition. When inspecting bearings they have to be taken out of their conventional positions, with regard to fitting on the crankshaft journal, at a clean surface to match any troubles with the bearings. Contaminants can be carried into the engine during assembly, through the filters or as a result of machining and can become lodged in the bearing material and larger particles can cause scoring. To avoid such failures it is necessary always to clean all the parts of the vehicle and often change the oil and filters. Lubrication breakdown may be attributed to heat, loading, leakage and blockage of the passages and such effects are violent where the bearing material is squeezed from its matrix. They also affect bearing durability; for example, loading the engine or short running wears and corrodes the bearings. Further, behaviours such as having bearing surfaces overly tight or entrapping contaminants will yield to inadequate oil supply and failure.