Bearing failure can occur due to lack of lubrication, dirt particles, motor overload and corrosion. Regardless of the nature of the defects, the cause of the damage to the liners must be eliminated during the engine overhaul to avoid recurrence.
For inspection, remove the bearing shells from their beds in the engine block/connecting rod heads and main/connecting rod caps and lay them in order of installation on a clean work surface. The organization of the placement of the liners will make it possible to link the nature of the identified defects to the state of the corresponding shaft journals.
Dirt and foreign particles enter the engine in various ways. They can be left inside the unit during assembly of the unit, or they can get through filters or the crankcase ventilation system. All particles that get into the engine oil eventually end up in the bearings sooner or later. Often, metal filings are embedded in the soft material of the liners, which are formed during the normal operation of the internal components of the engine. There is a high probability of the presence of traces of abrasive in the bearings, especially when due attention was not paid to cleaning the block after the completion of the engine reconditioning. Regardless of the way in which foreign particles enter the engine, they are highly likely to be embedded in the soft surface of the crankshaft bearing shells and are easily identified by visual inspection of the latter. Large particles usually do not linger in the liners, but leave noticeable marks in the form of scratches, cavities and scuffs on their surface and the surface of the shaft journals. The best guarantee against this kind of trouble is a responsible attitude to cleaning components after the completion of an engine overhaul and careful attention to cleanliness during assembly. Frequent, regular engine oil changes can also significantly extend bearing life.
Oil starvation can result from several different but often related phenomena. So, overheating of the engine leads to dilution of the engine oil and its displacement from the working clearances of the bearings. Lack of bearing lubrication can be attributed to excessive running clearances as well as normal leaks (internal or external). A common cause of oil being forced out of bearing clearances is constant over-revving of the engine. Violation of the patency of oil flows (usually associated with misalignment of holes when installing components) also leads to a reduction in the supply of lubricant to the bearings. A typical result of oil starvation is complete or localized wiping/tearing of the surface layer of liners from the metal substrate. In this case, the operating temperature may rise to such a level that the substrate acquires a bluish tint as a result of overheating.
The driving style of the car owner also has a significant impact on the service life of the bearings. Driving at low speed in high gear leads to significant overloads of the bearings, accompanied by the displacement of the oil film from their working gaps. This kind of overload leads to an increase in the plasticity of the liners and the appearance of cracks in the surface layer (fatigue strain). In this case, the surface material begins to crumble and separate from the steel substrate. Operation of the car in the urban cycle (frequent trips over short distances) leads to the development of bearing corrosion due to the fact that insufficient heating of the engine leads to condensation and the release of chemically aggressive gases. These products accumulate in engine oil, forming slags and acids. If such oil gets into the bearings, aggressive substances contribute to the development of corrosion of the liners.
Improper installation of liners during engine assembly can also cause their rapid destruction. Too tight fit does not provide the required working clearance of the bearings, which leads to their oil starvation. The result of falling under the liners during the installation of foreign particles is the formation of elevations, the surface layer from which is quickly wiped off.
Insert selection
If the main bearing shells are worn or damaged, or if the correct operating clearance cannot be achieved (see Installing the crankshaft and checking the operating clearances of the main bearings or Installing connecting rod and piston assemblies and checking the working clearances in the connecting rod bearings of the crankshaft), the situation can be corrected in the way described below, by selecting and installing new liners. If the crankshaft has been machined, it must be equipped with liners of the appropriate repair (with humiliation) sizes - usually the selection of liners is carried out by specialists who made the groove of the shaft necks. Regardless of the method used to determine the required bushing size, the running clearances of the bearings must then be checked using the Plastigage measuring set (see below).
Note. If it is not possible to properly correct the value of the working clearances by selecting the liners, the shaft must be replaced.
Main bearings
1. If you need new STANDARD size earbuds, choose one that has the same color coding as the old one.
2. If the color coding of the old bushing is lost, look for the marking embossed on the block for the journals of the main bearings (see accompanying illustration).
3. Also check the marking of the class of main bearings on the shaft itself (see accompanying illustration). 4. When selecting new earbuds, use the color coding identification card (see below).
A | B | C | D | |
1 | RED | PINK | YELLOW | GREEN |
2 | PINK | YELLOW | GREEN | BROWN |
3 | YELLOW | GREEN | BROWN | BLACK |
4 | GREEN | BROWN | BLACK | BLUE |
Connecting rod bearings
1. When selecting new STANDARD size earbuds, also use the color coding.
2. If the color code on the old bushings is lost, look for the markings on the lower heads of the connecting rods (see accompanying illustration). The label in the form of a number characterizes the size class of the connecting rod bearing (should not be confused with the cylinder number).
3. Also check the letter marks on the shaft itself (see accompanying illustration).
4. When selecting new earbuds, use the color coding identification card (see below).
A | B | C | D | |
A or I | RED | PINK | YELLOW | GREEN |
B or II | PINK | YELLOW | GREEN | BROWN |
C or III | YELLOW | GREEN | BROWN | BLACK |
D or III | GREEN | BROWN | BLACK | BLUE |
All bearings
Remember that the final parameter that determines the correct selection of liners is the result of measuring the operating clearances in bearings. If you have any questions feel free to contact the representatives of the branded service center of Honda.