 | 1. Despite the fact that the crankshaft bearings during engine overhaul must be replaced on a mandatory basis, the old liners should be maintained for the purpose of scrutiny of their condition, the results of which can give a lot of useful information about the general state of the engine. The illustration shows examples of typical defects of bearing shells. |
2. bearing failures can occur due to lack of grease, dirt particles overload the engine and corrosion development. Regardless of the nature of the defects, the cause of damage to the inserts should be eliminated in the process of fulfillment of major overhaul of the engine in order to avoid relapse.
3. For inspection, remove the bearing shells from their beds in the engine block / bottom heads of rods and indigenous / connecting rod caps and place them in order of installation on a clean work surface. Organization placing inserts allow to tie the nature of the identified defects to the state of the corresponding necks of a shaft.
4. The dirt and extraneous particles get to the engine various ways. They can be left inside the unit during assembly of the unit, or to penetrate the filter or the crankcase ventilation system. All particles that enter the motor oil, ultimately, sooner or later end up in the bearings. Often soft material inserts embedded metal particles formed during the normal operation of the internal components of the engine. Chances bearing traces of the presence of an abrasive, especially when it was not paid due attention to cleaning the unit after the completion of repair of the engine. Regardless of the manner in which foreign particles enter the engine, as a result they are highly likely to turn out to be embedded in the soft surface of the crankshaft bearing shells, and easily identified by visual inspection of the latter. Large particles usually do not stay in the inserts, but leave them on the surface and the surface of the necks of a shaft appreciable traces in the form of scratches, cavities and burrs. The best guarantee of this kind of trouble is a responsible attitude to the cleaning of components after the engine overhaul and thoroughness of cleanliness during assembly. Frequent regular change of motor oil also can significantly extend the service life of the bearings.
5. oil starvation may result from a number of different but often interrelated phenomena. For example, engine overheating leads to a dilution of the engine oil and oust him from working backlashes of bearings. Lack of lubrication of the bearings may be due to the excessive size of working backlashes, as well as the usual leaks (internal or external). A frequent cause of displacement of oil from the bearing clearance is a constant excess of turns of the engine. Violation cross maslotokov (usually related to improper hole alignment when installing components) also leads to a reduction of lubrication for bearings. A typical result is a full oil starvation or local wipe / vyscherblivanie surface layer liners with a metal substrate. At the same time the operating temperature can be raised to such a level that the substrate as a result of overheating becomes bluish.
6. Significant impact on bearing life has also peculiar manner of driving of the car owner. Movement at a low speed overdrive causes significant overload bearings, accompanied by the displacement of the oil film from running clearances. Such overload lead to increased plasticity liners and crack initiation in the surface layer (fatigue deformation). When this surface material begins to crumble and be separated from the steel substrate. Operation of the vehicle in the urban cycle (frequent trips on short distances) leads to the development of corrosion of bearings due to the fact that insufficient heating of the engine results in condensation and isolation of chemically aggressive gases. These products accumulate in the engine oil, and the slag forming acid. If you get this oil in bearings aggressive substances contribute to the development of corrosion liners.
7. Improper installation of inserts during assembly of the engine and can cause rapid destruction of them. Too tight fit does not provide the desired amount of a working backlash of bearings that leads to starvation of oil. The result of exposure to the ear (in the process of installing them) foreign matter is the formation of elevations, the surface layer which quickly wiped. |
