What is the Reason for the Abnormal Noise of Connecting Rod Bearings?

As a Changan Fan Assy Expoter China, share with you.

01

Fault phenomenon

When the engine is idling, there is no abnormal noise or the noise is small, and there is a heavy and short "Dangdang" obviously continuous knocking sound during rapid acceleration. This is the main feature of the connecting rod bearing ringing, when the idling speed is serious, a clear ringing can also be heard. The noise of connecting rod bearings is crisper, softer and shorter than that of main bearings.

02

Failure analysis

① The connecting rod bearings or journals are worn, making the fit gap too large or the fit poor.

②The oil pressure is too low, or the engine oil is deteriorated, or the connecting rod shaft oil passage is blocked, resulting in poor lubrication.

③ The bolt of connecting rod bearing cover is loose or broken.

④ The dimensions of the connecting rod bearings do not match, causing rotation or breakage

⑤ The friction-reducing alloy of the connecting rod bearing falls off or burns.

Changan Connecting Rod

03

Troubleshooting

① Change the engine speed, the noise is smaller at idle speed, more obvious at medium speed, slightly steady increase the continuous knocking sound of the throttle valve, the knocking sound increases during rapid acceleration, and it is not obvious at high speed due to other noise interference.

②The load increases and the noise increases.

③When the engine temperature changes, the noise usually does not change, but sometimes it is also affected by the temperature of the lubricating oil.

④ The sound of the single cylinder is cut off, the sound is obviously weakened or disappeared, but when the fire is resumed, the sound can immediately appear on the cylinder. However, when the connecting rod bearing is too loose, there is no obvious change in the sound of single cylinder misfire

⑤ Ignite once, sound twice, that is sound twice every working cycle.

⑥ The noise of connecting rod bearing is larger on the side of the oil pan.

If the stethoscope is touched on the body for diagnosis, the sound is not very clear, but the sound of the connecting rod bearing knocking can be clearly heard at the oil filler port or the crankcase ventilation pipe port.

⑦Concomitant phenomenon.

The noise of the connecting rod bearing is accompanied by a significant decrease in oil pressure, and the body vibrates seriously in the field. This is different from the piston pin sound and the piston knocking on the cylinder. You can use your hand to hold the screwdriver or stethoscope against the lower part of the cylinder or the oil pan. When you touch the corresponding faulty cylinder, there will be a noticeable vibration.

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