To reduce crank pin wear, the con rod bearing is attached to the crank pin. The cross-head con rod’s big end bearing is frequently constructed independently and then secured with the con rod bolt and the rod body, which is frequently directly cast on its inner surface. Anti-friction alloy big-end bearing with no cross-head connecting rod, with the upper half of the bearing cover constructed in one piece with the shaft and the lower half fabricated separately, with the upper half secured with connecting rod bolts.
Today’s article will introduce you to the reasons for the abnormal noise of the connecting rod bearing. If your engine also has the following conditions, then go check it out and replace it with new parts. In Landtopmall, the con rod bearing D782 has been selling particularly well recently.
The main reasons for the sound of con rod bearings are: ablation and falling off of bearing alloys; wear of bearings and journals; loose bearing cap bolts; bearing rotation, etc.
(1) Failure Occurrence
- A soft and brief “dang dang dang” percussive sound occurs after the motor is started.
- The sound does not alter as the engine temperature changes.
- The sound is clear when the engine is running at medium speed; when the engine is quickly increased, there is a constant and audible knocking sound.
- When a bearing is really loose, it might generate a “squeaky edge” sound.
- The sound is louder on the crankcase side.
(2) Inspection Procedure
1 Conduct a fire test one by one with a screwdriver while the engine is running at medium speed to locate the source of the noise.
2 When you reach the point where the knocking sound can be heard, release the accelerator pedal, insert a rubber hose into the oil filling pipe, and test each cylinder with a screwdriver to find the source of the noise.
3 Start the engine and touch the position of each cylinder in the crankcase with a screwdriver to see whether there is any vibration.
4 Drain the lubricating oil in the oil pan, remove the oil pan, and inspect each cylinder for loose bearings.
(3) Check Con Rod Bearing Clearance
The crankshaft bearing clearance and con rod bearing clearance, that is, the clearance between the crankshaft journal, the connecting rod journal, and its bearing bush, can be determined by measuring the outer diameter of the journal and the inner diameter of the bearing hole respectively; when measuring the inner diameter of the bearing hole, first install the bearing bush on the bearing seat hole and bearing cover, fasten the bearing cover, and tighten the fixing bolts according to the specified torque (female), and then measure the inner diameter of the bearing hole. The difference between the large inner diameter value of the bearing hole and the small inner diameter value of the journal is the bearing clearance. If the clearance exceeds the standard, the bearing bush should be replaced. If the clearance still exceeds the standard after replacing the new bearing bush, the crankshaft journal and connecting rod journal should be polished or replaced with new parts.
Inspection of Con Rod Bearing Clearance
- Theoretical Method: First, the job of disassembly is completed. The first step is to remove a connecting rod bearing cap and scrub the bearings and journals; second, a plastic gap is cut correspondingly through the length of the journal and placed in a direction parallel to the connecting rod axis; and finally, the gap’s width can be measured with the appropriate material.
- Practice Method: Shake the crankshaft so that the examination point is below, then tap the connecting rod bearing cover gently along the bottom with a tool. The big end of the connecting rod should be able to move after pushing it by hand; otherwise, there will be an excessive clearance error.
- AdjustmentMethod: This is known as tile scraping, and it is a time-consuming process. Mostly by disassembling the necessary pieces, using the corresponding documentation, and using an instrument to check the gap. We can discover a corresponding repair shop to provide professional treatment during this process because many little gaps directly impair your driving safety.
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