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When we find that the valve part of the automobile engine has abnormal noise, we can analyze and deal with it through the following four steps to find out the cause of the abnormal noise, which can effectively solve the problem.
1.Abnormal engine valve noise
Cause:
Valve clearance adjustment is too large; Valve clearance adjustment bolts loose; Rocker arms at valve clearance wear into grooves; Push rod bending; Stele or CAM wear.
Diagnosis:
diesel engine idle, in the valve chamber can hear the "tap, tap" sound, sound does not change with the temperature of the diesel engine, single cylinder fire sound does not change, this situation can be diagnosed as the valve ring.
Exclusion:
Remove the valve chamber cover and check the valve clearance. If the valve clearance is too large, it indicates that the valve ring is caused by the valve clearance. It should be handled according to the detection situation.
2.Abnormal sound of engine valve tappet
Reason:
when the profile of the CAM is correct, it can ensure the movement of the valve lift and its lifting process. If the contour of the CAM surface is worn, the continuity of the contact between the valve tappet and the CAM is destroyed. When the valve is sitting, the valve tappet jumps and the CAM impact makes a sound. Diesel engine valve mechanism Dinghui temple disc CAM mechanism, camshaft rotation, in addition to the top of the valve tappet rise, but also will drive the valve tappet for lateral swing, when the valve tappet and casing radial wear, with the gap increased, the valve tappet for lateral swing and casing collision sound; In addition, there is no oil between the valve rocker arm adjustment screw and the upper end of the push rod, it is difficult to mitigate the impact, so there will be noise. A broken valve spring is also prone to sound.
Diagnosis and exclusion:
if the valve gap meets the requirements of technical documents, then the sound produced by the valve mechanism is mainly due to the wear of the CAM shape does not meet the requirements, the valve tappet and the conduit gap is too large, or the valve rocker arm adjustment screw without oil, or the valve spring is broken, should be identified and excluded.
3.Abnormal sound of timing gear
Reason:
diesel engine timing gear majority is not smooth transmission load, the impact of the formation of transmission, or gear transmission with outer profile wear and damage of the gear meshing correctly, tooth contact form part of the relative motion is changed, namely the increase of sliding friction, rolling friction reduction, wear and tear, thus sped up the gear tooth surface friction and impact, a noise. When replacing the transmission gear, there is a pair replacement, which not only accelerates the gear wear, but also produces incorrect meshing sound; Timing gear quality is poor, meshing is not correct and sound.
Diagnosis:
If the sound is similar to that described in the phenomenon, it can be basically determined as the timing gear sound.
Ruled out:
If the repair without changing gear in pairs, it is the cause of the timing gear produces sound, or timing gear quality is poor, cause timing gear ring, the former should be replaced in pairs, the latter should be to choose good quality gear, if use time is too long, the noise gradually appear, and from small to large, timing gear ring is caused by wear nothing, should be replaced.
4.Engine valve crown piston
Diesel engine valves are mostly mounted. The piston head valve should be kept at a certain distance. If this distance disappears, the piston head will collide with the valve and make a sound.
Cause:
Valve seat ring is too thick; The bottom of valve seat ring hole processing is not smooth or the depth is not standard; Valve head is too thick; Too small valve clearance; Piston type is wrong; Timing gear marks are out of alignment.
Diagnosis:
WHEN THE diesel engine is running, hear the sound mentioned above, and pinch the nut fixing the valve chamber cover with your finger, feel vibration, can be tentatively determined as the valve and piston collision ring.
Exclusion:
should be further disintegrated to identify, and processed. Do not do the fault reappearance test for a long time, so as not to damage the parts or cause greater failure of the diesel engine.
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