The big engine throttle of the excavator is noisy when it works. It's like whistling. The old driver who operated the excavator for many years must have encountered a similar noise in the engine. What causes the abnormal noise?
Relationship between abnormal sound and engine speed
The most common abnormal noise of engines depends on the speed of the engine.
(1) the abnormal sound exists only at idle or low speed.
The causes are: the gap between the piston and the cylinder wall is too large; the piston pin is too tight or the connecting rod bearing is tightly assembled; the clearance of the tappet and its guide hole is too large; the profile of the valve cam is worn; sometimes, the starting grasp is loosened to make the pulley sound (obviously when the speed is changed).
2. When a certain speed is maintained, the noise is disordered, and a short period of sound is issued successively.
The causes are: the camshaft timing gear breakage or its fixed nut loosening; the crankshaft broken; the piston pin bushing loose; the camshaft axial gap is too large or its bushing loose.
3. Abnormal sound occurs when the engine accelerates rapidly, and the sound still exists when the engine is running at high speed.
The causes are: loosening of the connecting rod bearing, burning of the bearing bush or the size of the shaft; the crankshaft bearing is loose or the bearing of the axle bush; the piston pin is broken; the crankshaft is broken.
The relationship between abnormal response and load
There is a significant relationship between a lot of noise and the load on the engine. The method of lifting the load by cylinder can be carried out in the diagnosis. The load of one or two cylinders is usually lifted by single cylinder or double cylinder breaking method in order to identify the relationship between the abnormal response and the load.
(1) when a certain cylinder is broken, the abnormal sound is no or less.
The reasons are: piston knocking; connecting rod bearing loose; piston ring leaking; piston pin broken.
(2) when a cylinder breaks off, the sound becomes heavier or no noise is heard.
The causes are: the loose copper sleeve of the piston pin, the excessive taper of the piston skirt, the running out of the piston pin, the loosening of the fixed bolt of the connecting rod bearing cap or the melting of the alloy of the connecting rod bearing, and the loosening of the fixed bolt of the flywheel.
(3) the intermittent two cylinders of adjacent cylinders were relieved or disappeared.
The cause of the ringing is: the crankshaft bearing is loose.
The relationship between the abnormal sound and the working cycle of the engine
The abnormal sound failure of the engine is often closely related to the working cycle of the engine, especially the abnormal response of the crank and connecting rod mechanism and the gas distribution mechanism is related to the working cycle. As far as the four stroke engine is concerned, all the sound caused by the crank and connecting rod mechanism is two times for the engine work once, and all the sound caused by the gas distribution mechanism is used once for the engine work once.
The reasons for the abnormal sound caused by the crank and connecting rod mechanism include the piston knocking on the cylinder wall, the percussion sound from the piston pin, the piston top cylinder cover, the looseness of the connecting rod bearing, and the leakage of the piston ring.
The reasons for the abnormal sound caused by the gas distribution mechanism are: the gap between the valve and the valve is too large; the clearance of the tappet and its guide hole is too large; the cam contour is worn out; the gap between the valve rod and its catheter is too large; the valve spring is broken; the radial rupture of the camshaft timing gear; the valve seat ring loosening; the valve card's stagnation can not be closed.
If the abnormal sound has nothing to do with the work cycle, we should pay attention to the area of the noise. Usually, the noise caused by a gap that is irrelevant to the working cycle is mostly the failure of the engine accessories; if the continuous metal friction from the work cycle independent of the machine parts, it is considered that some revolving parts are malfunction.
The relationship between abnormal sound and temperature
When the temperature rises, the sound will lighten or even disappear.
The reasons are: the clearance between the piston and the cylinder wall is too large; the piston is inaccurate due to the depth and width of the main bearing oil groove; the oil pressure is low and the lubrication is bad.
2. When the temperature rises, there will be a sound, and the sound will lighten or disappear after the temperature is lowered.
The causes are: the early ignition caused by overheating; the long and short axis of the ellipse of the piston skirt is opposite; the piston ellipticity is small, the gap between the piston and the cylinder wall is too small; the piston is deformed; the gap between the piston rings is too small.
Relationship between abnormal sound and engine position
When the engine has abnormal noise, it will produce a certain degree of vibration. According to the characteristics and location of vibration, it can help diagnose the cause of abnormal noise.
Speaking of engine abnormal sound, it may make many excavators master headache, yes, engine abnormal sound has been a stubborn disease of excavators. When the engine makes a strange noise, it is necessary to shut down to check what causes the engine abnormal noise, find out the cause and deal with it in time.
