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Main and connecting rod bearings

Checking the Status

Despite the fact that the main and connecting rod bearings at engine major repairs must be replaced, which were in operation the bearings should be stored at the place of installation for a thorough check, as traces of wear on these details allow you to restore the general condition of the engine. The bearing shells are divided into size groups in thickness, belonging to each size group contains color-coded printed on the liner.

The reasons for the destruction of the crankshaft bearings are poor lubrication, the presence of dirt and foreign particles, motor overload and corrosion. Whatever the reason, caused destruction of bearings, it should be removed before final assembly of the motor, to avoid repeated damage these parts.

When checking the condition of the bearings they need to get out of the cylinder block, crankshaft bearing caps of the crankshaft, connecting rod caps and connecting rods. Put the shells on a clean surface in the same order in which they were installed on the engine. This will set the proper support of the crankshaft, wherein the bearing is subjected to increased wear. When checking is not permitted touching fingers to the working surface of the liner, so as not to damage them further.

Dirt and debris fall into the engine for various reasons - in the assembly process, through filters or crankcase ventilation system. Contaminants can also get into the oil, and from it - in bearings. Often, contamination from metal particles are present machining engine parts, or due to wear during normal operation of the engine. Sometimes at pollution there remains of abrasive materials after the lapping and grinding works, especially at insufficient washing and cleansing the engine after. Regardless of the cause of origin of foreign contamination is usually introduced into a soft alloy of the bearing and are easily distinguishable. Large particles can not penetrate into the bearing and lead to scratching and scuffing on the surfaces of both the bearing and the necks of the crankshaft. The best way to prevent such deterioration is careful washing of parts and maintaining impeccable cleanliness during engine assembly. In order to prevent premature wear and recommend more frequent oil changes and filters.

Insufficient lubrication of the engine ("oil starvation") can be caused by a number of interrelated reasons. These include motor overheating (causing oil dilution), overload (cause squeezing oil from the surface of bearings) and pressure drop due to leakage (emission) of oil (due to increased clearance in the bearings, wear of the oil pump, the big frequency of rotation of the crankshaft) . The reason for the accelerated wear of the bearings of the crankshaft and is blocking of oil channels, usually due to misalignment lubrication holes in the bearings of the crankshaft with the holes in the cylinder block and crank, causing insufficient lubrication of the bearings and out of order. When the cause of failure is a lack of lubrication, there is a wipe or extrusion coating material bearing with a steel base. The temperature rises to such a level that overheating occurs chipping steel base bearing, which acquires a bluish tint.

The durability of the crankshaft bearings also depends significantly on the skills of driving. Bearings are experiencing increased stress when driving at full-throttle or low speed to a higher gear (heavy engine modes). At high loads occur squeezing the oil film. Bearings experience flexural deformation which microcracks (fatigue wear). Typically the coating is detached from the bearing steel substrate in the form of fine particles.

Travel a short distance can cause corrosive wear of bearings as because of insufficient warming do not have time to leave the condensed moisture and gases, corrosive. These components are accumulated in the oil, causing the formation of acid and insoluble precipitates. To the extent that oil going to the bearings corrosion by acids, causing the destruction of bearings and their failure.

Improper installation of the bearing during assembly and leads to premature wear. If the bearing clearance is less than the norm, then their lubrication is difficult, which leads to wear as due to the "oil starvation." Dirt or small particles that fall under the bearing, lead to a local elevation of the insert and to increased wear in this part.

When assembling do not touch the surface of the insert, otherwise you may scratch the surface or to place on the insert the dirt particles.

As already mentioned, at engine major repairs liners indigenous and connecting rod bearing must be replaced. Failure to do so and saving on repair lead to extremely undesirable consequences.