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Engine appear abnormal sound analysis of the reasons

Thrum abnormal engine is mainly due to the crank link mechanism and gas distribution agencies fault happens, the basic reason for loose wear, deformation, fasteners, improper adjustment, or damaged. In addition, the damage of the turbocharger can also lead to different ring.

A crank connecting rod mechanism failure.
1. The piston type cylinder.
When engine working, the piston and cylinder wall collision and the sound from a called “knocking. Phenomenon is:
(1) the idle running, send out “when, when” rhythmic sound.
2 noise decreases with temperature rise or disappear.
(3) out of the blue and white smoke.
(4) sometimes is not easy to start or engine power down.

Analysis:
(1) the piston and the cylinder wall with the gap is too large.
When the engine operation is divided into the intake, compression, for power and exhaust four-stroke, in compression, the compression for the power stroke, the gas force on the piston, therefore, in the compression stroke, the piston at the top of the presence the gas pressure, the piston up over the bottom dead point, the piston is pressed against the cylinder side (right side) of the compressed gas; as the power stroke, the combustion of the explosive gas so that the piston over the top dead point, the connecting rod inclined side pressure. the piston is pressed against the cylinder on the other side (left side).
The pressure of the gas piston is pressed against the cylinder wall, the reciprocating motion of the piston, the piston and cylinder wall wear, over time, will increase the clearance of the piston and the cylinder wall.

(2) connecting rod distortion.
When the operation of the engine, the connecting rod for high-speed swing, to withstand the gas pressure, the inertial force and the rotation from the force, but the force is varied, it is easy to cause distortion; engine also caused even in the case of overload or incomplete combustion normal, rod distortion.
After the rod is distorted, the little-endian and big-endian two axes not parallel to the rotation is not in the same plane, so the piston when the commutation, it will collide with the cylinder wall beep.
⑶ rod small end pin sets the piston pin, connecting rod bearing journal with tight piston commutation, not smooth smooth transition, but unaccommodating swing, also cause the piston to hit the cylinder wall, beep.
(4) piston damage or the piston anti oval can also cause piston knock. Oil-free piston radial clearance, the piston knock will be more obvious.
2. Piston pin ring.
Phenomenon: when the engine is running, the piston pin with vice (piston pin and piston pin bore, piston pin and pin sets) impact with a sharp “a little child, a little child” sound, known as the piston pin ring at idle when slightly refueling clearer.

Analysis:
Operation of the engine, the piston due to the gas pressure withstand greater impact load, impact load also causes the piston pin and pin sleeve, piston pin and piston pin seat hole clamping with time due to wear and the mating gap increases, and exceeds the allowable value, when the piston reciprocating motion, the acceleration magnitude and direction of change with the movement of the piston position changes, the piston pin and the pin sleeve and the piston housing surface will also change, so the piston pin and the sleeve in change the pressing surface occurs when the impact on the sound. Piston pin and with almost no lubricant, the sound will be more obvious.
3. Connecting rod bearing ring.
Connecting rod bearing ring connecting rod bearing and journal impact loud noises, commonly known as small-watt sound. The phenomenon is:
(1) engine work, the issue of “when” rhythmic metal percussion.
(2) single-cylinder off the fire sound to reduce or disappear.
(3) abnormal sound increases with the load increase, with the speed increased with the increase.
⑷ sometimes accompanied by a decline in oil pressure.

Analysis:
(1) connecting rod bolts loose: connecting rod bolt loose rod journal with the gap increasing.
(2) engine maintenance, the connecting rod bearing clearance mismatch is too large.
⑶ wear: during engine operation, due to the gas pressure of the top of the piston, the piston through a piston pin on a connecting rod and crankshaft connecting rod journal pinch inertial force generated when the piston reciprocates, and the big end of the connecting rod the joint action of the centrifugal force generated with the rotation of the crankshaft, the connecting rod bearing journal the pressing force increases, also increases the amount of wear of the connecting rod bearings and crank journal, with time, corresponding with the gap increases. If the rod journal lubricants clogging caused by poor lubrication will accelerate the connecting rod bearing and journal wear process increases with the gap.

4.Crankshaft main bearing rang.
(1) Combined crankshaft.
135 diesel engine crankshaft by the multi-section song Shui bolt combination, the two zig-sets of roller bearing crankshaft main bearings. The sound of rolling bearing and the radial clearance is too overextended a particularly sharp, shrill voice, the operation will be issued when the throttle is clearer. If the crankshaft Rolling radial gap is too large, the operation will be issued the “Huo Huo” sound.
⑵-piece crankshaft.
Sudden acceleration of the engine, it will send a heavy and powerful “At first, just metal percussion, severe body vibration, sound with the load increases, the two adjacent cylinders off the fire, and its voice weakened or disappeared, with oil pressure drop.

Analysis:
Crankshaft main bearing ring is because of their bearing journal with the gap is too large. During operation of the engine, forming a force due to the gas pressure of the piston at the top and piston rod, centrifugal force generated by the rotation of the inertial force generated by the piston pin and the crankshaft, and the crankshaft main journal and the bearing generating percussive sounds. Two main reasons:

① wear: crankshaft main bearing wear due to the long time to work, resulting with the gap increasing; poor quality lubricants, engine temperature is too high or the load is too large causes poor lubrication, but also make the crankshaft main bearing journalincreased wear and tear, with the gap increasing.
(2) If the crankshaft main bearing cap bolts loose, so that the crankshaft main bearing wear intensified, with the gap increasing.
5. The crankshaft axial movement of the hair ring.
Crankshaft bearing ran phenomenon of abnormal sound crankshaft main bearing ring.
Analysis:
The crankshaft must have a certain axial gap, therefore, the axial force before and after the traverse, to traverse in order to limit the front and rear crankshaft Usually the crankshaft Tops finite bit thrust pad. When the operation of the engine, the crankshaft rotates, the inevitable wear of the thrust pad, when the the thrust pad thinning axial gap increases to a certain extent, the front and rear crankshaft runout abnormal noise caused by impact.
II. Gas distribution agencies abnormal sound.
1. Valve sound.
Valve ring is the operation of the engine, the valve stem to the top of the rocker arm collision issued sound, that is, when the engine is idling, you can hear the cylinder head issued by the rhythmic “tick, tick” sound.

Analysis:
Top valve stem and rocker arm to allow proper clearance (to prevent the push rod and valve caused by thermal expansion valve closed lax), the detailed provisions of the size of the gap in the engine manual. If the valve clearance is too large, the engine work will beep. The valve clearance is too large:
⑴ valve clearance adjustment is too large.
(2) valve clearance adjustment bolts loose.
(3) valve rocker arm wear into a concave shape.
(4) valve push rod bending.
2. Valve tappet ring.
The valve lifter ring is collision issued with the sleeve in the lower end of the valve lifter and cam hit or valve lifter swing, rhythm similar valve “tick, tick” sound. The engine idling clearer.
Analysis:
⑴ cam surface contour shape wear. The outer profile of the cam is correct, to ensure the continuity of movement of the valve lift and the lifting process, then the continuity of the valve rod guide and the cam of the contact will be destroyed if the shape of the cam surface contour wear, when the valve is seated, the valve lifter beating lever and cam impact sounds.
(2) camshaft rotates, the valve lifter rise, but also on the camshaft rotation direction transverse swing. If the valve lifter sleeve radial wear with the gap increasing lateral oscillation valve lifter sleeve collision sounds.
(3) If the valve push rod upper end of the oil, valve rocker adjusting screw and the top of the putter issued due to dry friction “chirp, chirp” sound. Valve spring break also easy to produce sound.
3. Transmission gear ring.
Phenomenon: when the engine is working, at the front of the engine drive gear chamber cover is making an unusual sound.
Analysis:
(1) The engine is in operation, the drive gear and more by not smooth drive load, impact on the formation; gear tooth wear, undermining the proper meshing of the gear. Therefore, accelerated wear of the tooth surface, sliding friction and impact, beep.
⑵ If you replace the drive gear, not be replaced in pairs, not only accelerated gear wear, while there will be abnormal engaging sound.
(3) transmission gear is of poor quality, to meshing incorrect beep.
4. Valve collisions piston ring.
Phenomenon: the operation of the engine, the engine is the upper part of the cylinder head ridden and rhythmic percussion hand Qingnie valve chamber cover lock nut, the feeling of collision.
Analysis:
⑴ valve seat is too thick, the valve head sticking out too much.
(2) valve seat hole machining the bottom is not flat or sub-standard depth, resulting in valve seat higher.
(3) valve head is too thick.
(4) valve clearance is too small.
⑸ piston model errors.
(6) with gas agencies timing gear mark is not aligned.

III.Turbocharger abnormal sound.
Phenomenon: the operation of the engine, turbocharger abnormal noises.
Analysis:
1. Rotor out of balance.
Turbocharger rotor speed is high, so the the rotor static balance and dynamic balancing requirements are particularly stringent, if the rotor is balanced during manufacture ultra-poor or improper assembly, resulting in unbalanced rotation, work will cause vibration and beep.
If the turbocharger into the foreign body, the rotor impeller damage, cause the rotor to lose balance makes strange noises.
2. Bearing wear.
If the rotor bearing wear, so that the rotor axis is tilted, the centerline of the rotor axis do not coincide with the center line of the shaft hole, an abnormal sound easy impeller and casing scraper.
If the temperature or an external force booster also cause deformation of the casing, the impeller of the scraper and generation of abnormal noise.

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