Causes of Damage to Engine Sliding Bearings

      Engine crankshaft, connecting rod, camshaft bearing more use of sliding bearings. The 

sliding bearing is composed of steel back and alloy layer, in which the alloy layer is divided 

into aluminum alloy and copper base alloy.

     1.Lubricant mixed with impurities

     During the operation of the engine, if the impurities into the lubricating oil, will cause 

the crankshaft and connecting rod sliding bearing alloy layer wear. These sources of impurities 

have the following three channels´╝Ü

     One is the assembly of the engine when the metal residue in the body of the debris, cotton 

yarn feathers, coke particles. The second is the engine work wear down the metal particles, as 

well as fuel, lubricants in the sediment. The crankcase ventilation device enters the tiny dust. 

These imputities with the oil into the alloy layer surface, the coarse particles in the alloy 

layer surface will put out the groove, fine particles like abrasive wear alloy layer, thereby 

accelerating the alloy layer damage.

     2.Poor lubrication

     When the engine is running, the lubricant does not reach the surface of the sliding bearing 

and the journal, which will cause damage to the alloy layer. The specific situation generally have

 the following four: First, the angine starts immediately after the high throttle high-speed 

operation. Second, the engine in the oil pressure is too low under the conditions of high speed,

 heavy load operation. Third, improper selection of lubricants, seasonal changes in timely 

replacement and deterioration of lubricants. Fourth, the winter engine is not warm up to the 

start.

     3.Improperly assembled

      Improper assembly will cause the sliding bearing and journal with the gap is too large or 

too small, may also cause the sliding bearing dislocation, indexing.

      If the sliding bearing and journal with the gap is too small, in the engine running, will 

cause friction surface lubrication and poor heat dissipation. After the journal is thermally 

expanded, the gap can be further reduced. At this time, if the engine speed is not high, usually 

lead to engine stall, if the engine to continue high-speed operation, will lead to tile.

     If the connecting rod sliding bearing and the journal assembly gap is too large, the engine 

work stroke, the connecting rod journal of excessive impact will act on the connecting rod 

sliding bearing ("smashing"), resulting in sound (tumbling). The "smashing", the oil film is 

damaged, the friction surface direct contact, lubricating oil film lubrication, cushioning and 

cooling effect instantly disappear. As the impact of the connecting rod journal directly  on the 

alloy layer, and ultimately cause the alloy layer flanging, out block.

     If the sliding bearing assembly dislocation, translocation, will cause the sliding bearing 

coaxial reduction, stress concentration and poor heat dissipation, and even lead to tile or roll 

tile.

     4.The relevant parts of the error is too large

     Related parts of the error is too large, divided into the following three cases: First, the 

crankshaft main journal and connecting rod journal grinding and the use of the process of 

roundness, cylindrical degree of error is too large. The second is due to crankshaft bending 

deformation and even rod bending, distorion, resulting in cylinder center line and the crankshaft 

perpendicularity error is too large. Third, before and after the crankshaft perpendicularity 

error is too large. 

     Crankshaft and connecting rod sliding bearing caring, roller and tile and other serious 

damage, it should immediately stop and take remedial measures, or in the role of the engine under

 the action of inertial force, will occur connecting rod bolts, connecting rod rejection and 

other vicious accidents.