20.1. Typical signs of bearing failure
2. Bearing failure may occur due to lack of lubrication, dirt and other foreign particles, motor overload and corrosion. Whatever the cause of the bearing failure, it must be corrected before the engine is reassembled to prevent it from happening again.
3. When inspecting the bearings, remove them from the cylinder block, main bearing caps, connecting rods, and connecting rod caps and lay the bearings on a clean surface, positioning them as they were installed in the engine. This will allow you to link any bearing defects to the corresponding camshaft journals.
4. Dirt and other foreign particles enter the engine in various ways. They can be introduced into the engine during assembly or get through filters or the crankcase ventilation system. Dirt can get into the oil, and with it into the bearings. Often there are metal particles associated with the processing of parts or normal engine wear. After remanufacturing operations, abrasive particles may remain in the engine, especially if parts have not been thoroughly cleaned using the recommended methods. Regardless of their source, these foreign particles often end up burrowing into the soft bearing material, where they are easily visible. Large particles cannot penetrate the bearing and will scratch and damage the bearing and journal. The best way to prevent this cause of bearing failure is to thoroughly clean all parts and maintain impeccable cleanliness during engine assembly. In addition, frequent and regular changes of engine oil and filters are recommended.
5. Lack of lubrication (or loss of lubricating properties) due to a number of interrelated reasons. Excessive heat (which reduces the viscosity of the oil), overload (in which grease is squeezed out of the bearings), oil leakage or ejection (due to too large bearing clearances, oil pump wear or high vehicle speeds) - all this can lead to insufficient lubrication. Blockage of the oil passages, which is usually the result of misalignment of the oil holes in the bearing housing, also impairs lubrication and destroys the bearing. When the cause of bearing failure is lack of lubrication, the bearing material is abraded or extruded from the steel base of the bearing. The temperature may rise so much that the steel base will take on a blue tint due to overheating.
6. Driving style also affects bearing life. Full "gas", driving at low speeds (wrong gear selection), are the cause of excessive loads on the bearings, which can lead to extrusion of the oil film. These loads deform the bearings, which leads to the formation of small cracks on their surfaces (fatigue failure). Eventually, the material breaks into pieces and wears away from the steel base. Frequent short trips lead to corrosion of the bearings, since insufficient engine warm-up does not help to remove condensed water and corrosive gases. These substances enter the engine oil, forming acid and carbon deposits (soot). When such oil enters the engine bearings, the acid destroys them and contributes to the corrosion of the bearing material.
7. Incorrect installation of the bearing when assembling the motor will also lead to the destruction of the bearing. Too much "tight" the fit of the bearings leaves too small oil clearances, resulting in insufficient lubrication. Dirt or debris trapped behind the bearing shells will cause raised spots on the bearing, leading to bearing failure.