2. Bearing failures may be due to insufficient lubrication, contamination, engine overheating or corrosion. Any cause of failure must be corrected before engine assembly to prevent recurrence.
3. When checking the bearing shells, remove them from the cylinder block, connecting rods and connecting rod lower head caps. Lay them out on a clean surface in the same order they were in the engine. This will allow you to compare the condition of the bearings with the corresponding crankshaft journal. When checking the surfaces of the bearing shells, do not touch them with your fingers to avoid scratching them.
4. Dirt and foreign particles enter the engine in different ways. They can remain in the engine after assembly, enter the engine through filters or the crankcase ventilation system. They can get into the oil and along with it - into the bearings. These can be metal filings from mechanical processing or normal engine wear products. Abrasive particles sometimes remain on parts after engine repair, especially if insufficient cleaning. Such particles often penetrate the softer bearing material and are easy to recognize. Large particles do not penetrate the material, but leave scoring on the bearings and journals. The best way to prevent such malfunctions is to thoroughly clean all units and parts and carry out assembly with maximum cleanliness. It is also recommended to change the oil and filter regularly.
5. Insufficient lubrication (or a faulty lubrication system) is caused by several interrelated factors. Excessive heating (which reduces the viscosity of the oil), overload (which causes the lubricant to be squeezed out of the bearing surfaces), and oil leaks (caused by increased bearing clearances, wear of the oil pump, or high engine speeds) all cause lubrication problems. Obstruction of the oil passages, which usually occurs due to improper alignment of the holes in the bearing shells, also reduces the supply of lubricant and can lead to bearing failure. Insufficient lubrication, which leads to a bearing defect, causes the bearing material to wear out or be squeezed out of the steel base. In this case, due to overheating, the color of the steel base may change to blue.
6. Driving style has a certain impact on the service life of bearings. Using the fully open throttle mode at low speeds leads to increased loads on the bearings and, accordingly, to the squeezing out of the oil film. Such loads cause softening of the bearings, which leads to the appearance of thread-like cracks on their surface (fatigue failure). In this case, the bearing material delaminates and separates from the steel base. Short-distance driving leads to corrosion of the bearings, since insufficient engine warm-up causes the formation of water condensate and an aggressive gas environment. These products penetrate the engine oil, forming acid and sludge. Therefore, when oil is supplied to the bearings, the acid causes their corrosion.
7. Incorrect installation of bearings during assembly also causes their failure. Tightening of bearings leads to a decrease in the working clearance and oil starvation. Dirt or foreign particles that get under the liner cause stains, which leads to failure. When assembling, do not touch the bearing surfaces with your fingers so as not to scratch the surfaces and not to bring dirt onto them.
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