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Causes of automobile camshaft wear
by：Yisheng
2021-06-09
There are many reasons for car breakdowns, and some are caused by long-term. Common failures of camshafts include abnormal wear, abnormal noise, and breakage. Symptoms of abnormal wear often occur before abnormal noise and breakage occur.
(1) The camshaft is almost at the end of the engine lubrication system, so the lubrication situation is not optimistic. If the oil pump has insufficient oil supply pressure due to reasons such as excessive use time, or the lubricating oil passage is blocked and the lubricating oil cannot reach the camshaft, or the tightening torque of the bearing cap fastening bolts is too large, the lubricating oil cannot enter the camshaft gap. Cause abnormal wear of the camshaft.
(2) Abnormal wear of the camshaft will increase the gap between the camshaft and the bearing seat, and the camshaft will move axially when it moves, causing abnormal noise. Abnormal wear will also cause the gap between the drive cam and the hydraulic tappet to increase. When the cam is combined with the hydraulic tappet, an impact will occur, which will cause abnormal noise.
(3) The camshaft sometimes has serious failures such as fractures. The common causes are hydraulic tappet cracking or severe wear, severe poor lubrication, poor quality of the camshaft, and rupture of the camshaft timing gear, etc. .
(4) In some cases, the failure of the camshaft is caused by human factors, especially when the camshaft is not properly disassembled and assembled when the engine is repaired. For example, when removing the camshaft bearing cover, use a hammer or a screwdriver to pry pressure, or when installing the bearing cover, the wrong position causes the bearing cover and the bearing seat to not match, or the tightening torque of the bearing cover fastening bolt is too large. When installing the bearing cover, pay attention to the direction arrow and position number on the surface of the bearing cover, and use a torque wrench to tighten the bearing cover fastening bolts in strict accordance with the specified torque.
Reasons for abnormal noise of camshaft
2) The camshaft bushing rotates.
3) The camshaft is bent and deformed.
4) The axial clearance of the camshaft is too large.
5) The camshaft bushing alloy burns or falls off.
Camshaft abnormal noise performance characteristics
Abnormal wear of the camshaft will cause the gap between the camshaft and the bearing seat to increase, and the camshaft will move axially , Resulting in abnormal noise. Abnormal wear will also cause the gap between the drive cam and the hydraulic tappet to increase. When the cam is combined with the hydraulic tappet, an impact will occur, which will cause abnormal noise.
1) When the engine is running at medium speed, the sound is obvious, and there is a dull “click, click” sound, which can be heard even when running at idle speed, but it seems to disappear when running at high speed.
2) There is no change in the sound during the single-cylinder misfire test.
3) There is vibration near the camshaft bearing bush when it sounds.
The method of judging the abnormal noise of the camshaft
The sound is clear at idling speed, the sound is obvious at medium speed, and the sound at high speed changes from clutter to weakened. Disappear, it can be determined as camshaft noise.
1) Make the engine run with the strongest noise, use a screwdriver to touch the vicinity of each bearing at the cylinder block for auscultation, if there is a dull sound with vibration, it is a cam
The bearing in this section of the shaft is loud.
2) There is no change in the sound of the misfire test, and the throttle is slowly changed. If the idling sound is clear, the sound is obvious at medium speed, and the sound at high speed changes from clutter to weak, it means that the axial clearance of the camshaft is too high. Large or loose bearings.
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