2.2.20. Check of a condition of radical and conrod bearings
In spite of the fact that at capital repairs radical and conrod bearings are subject to replacement, former bearings should be kept for attentive survey as it can give valuable information on a condition of the engine.
The failure of bearings happens because of a lack of lubricant, presence of dirt and other foreign particles, an overload of the engine and corrosion. Irrespective of a cause of failure of bearings, before assembly of the engine the reason that did not repeat again, has to be eliminated.
For survey remove bearings from the block of cylinders and from covers, take from rods and covers of rods, and then spread out on a pure surface in the same order in which they are installed in the engine. It will allow to compare problems in bearings with the corresponding neck of a bent shaft.
Dirt and other foreign particles get to the engine in the different ways. They can remain in the engine at assembly, or get via filters, or system of ventilation of a case (PCV). Dirt can get to oil, and from it - to bearings. Often there are metal particles after machine processing and because of normal wear of the engine. Sometimes after grinding of components of the engine there are abrasive particles, especially, if details are not exposed to careful cleaning with the corresponding ways. Whatever was the source, these foreign objects often are introduced in soft material of bearings and can be easily found. Large particles do not take root into the bearing, and put scratches or damages to the bearing and a neck. The best way to prevent such cause of failure of the bearing - carefully to clear all parts and at assembly to keep all components perfectly pure. Also frequent and regular replacements of oil and the filter are recommended.
Several reasons connected among themselves have a lack of lubricant (or the lubricant termination). The overheat (which reduces lubricant layer thickness), an overload (which squeezes out oil from a gap between the sliding surfaces) and leak of oil or its effluence (because of increase in gaps in bearings, wear of the oil pump or high turns of the engine) - all these reasons make the contribution to a lack of lubricant. The corked channels of lubricant appearing usually as a result of discrepancy of lubricant openings in a bearing insert also lead to insufficient lubricant of the bearing and its failure. If the lack of lubricant is a cause of failure of the bearing, then material of the bearing is used up or breaks from a steel substrate. Temperature can reach such point at which the steel substrate will become from an overheat of blue color.
The manner of driving can have a certain influence on bearing service life. Driving with completely open throttle on small turns (overloading the engine) creates very big loadings which seek to squeeze out an oil film on bearings. These loadings bend bearings that brings to emergence on the surface of bearings of thin cracks (refusal because of fatigue of metal). Sometimes material of the bearing weakens in some places and breaks from a steel substrate. Short trips lead to corrosion of bearings as at insufficient warming up of the engine there is no removal of condensate and the gases causing corrosion. These products gather in motive oil, forming acid and slime. When oil comes to engine bearings, acid influences material of bearings, leading to its corrosion.
The installation of bearings, wrong at assembly of the engine, also leads to failure of bearings. In hard bearings there is an insignificant gap for lubricant that will lead to insufficient lubricant. The dirt or foreign particles which got on a back surface of an insert of the bearing will lead to emergence of eminences on the surface of the bearing which will cause refusal.