Q: What are the causes and prevention methods for bearing failure during an engine overhaul?
A: When an engine is being overhauled, the main and connecting rod bearings should be replaced with new ones. Nevertheless, the old bearings must be kept for examination because they can tell a lot about the condition of the engine. Bearing failure may arise due to various causes including absence of lubrication, presence of dirt or foreign particles, overloading of the engine and corrosion. Regardless of the cause, avoiding future bearing failures requires that one rectifies the current failure before reassembling the engine. In referencing to any issues that may exist in relation to a corresponding crankshaft journal, these bearings should be taken from the engine block and main bearing caps as well as from connecting rods and rod caps and arranged on a clean surface in their original positions. Foreign material and dirt can enter into engines through improper assembly; passing by filters/PCV system or even present in oil. These particles sink into soft bearing material causing damage to it. This type of bearing failure can be prevented by regular cleaning of engine components and frequent oil and filter changes. Insufficient lubrication results from excessive heat; overloading; oil leakage or throw off; blocked oil passages etc. Such wiping leads to overheating when there is not enough lubrication whereby bearing material is wiped or extruded out from steel backing plates. Driving habits such as full throttle open throttle operation, short trip driving at low speeds in high gears also affect bearing life. Due to such habits we can experience high loads on bearings, which cause flexing, fatigue failure/corrosion. Poorly installed bearings during engine assembly like tight fitted bearings or trapped dirt/foreign particles have also been known to cause failures.