How to solve the abnormal noise of excavator engine

When the engine of an excavator breaks down, it is often accompanied by some abnormal noises. Old maintenance masters can basically judge what the fault is by experience. Here are a few fault cases, hoping to help.

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First, the valve seat ring

Phenomenon:

(1) Diesel engine is prone to noise during cold start.

(2) Sound has nothing to do with speed. Occasionally, there is a crisp sound, which will soon disappear. In severe cases, this kind of sound will appear frequently.

(3) Individual cylinders do not work when the sound appears, and return to normal after the sound disappears.

Maintenance of engine

Reason:

(1) The loose fit between the valve seat ring and the cylinder head is caused by too small interference.

(2) The material of the seat ring is not suitable, and the thermal expansion coefficient is too small.

Diagnosis and elimination:

(1) sounds, accompanied by the phenomenon that individual cylinders do not work; When the noise disappears and the diesel engine returns to normal, it can be diagnosed that the valve seat of the non-working cylinder is loose.

(2) Measure the cylinder pressure one by one with a cylinder pressure gauge, and the cylinder with low pressure is an abnormal sound cylinder.

Second, the camshaft ring

Phenomenon:

(1) When the diesel engine runs at medium speed, there is heavy noise on the camshaft side of the cylinder block; The noise is not clear at high speed.

(2) When the single cylinder is cut off, the noise remains unchanged.

(3) There is vibration near the camshaft bearing.

Reason for failure:

(1) The clearance between camshaft bearing and journal is too large and loose.

(2) The camshaft bearing is loose or the bearing alloy is ablated, peeled off or excessively worn.

(3) The axial clearance of camshaft is too large or the camshaft is bent.

Diagnosis and elimination:

(1) Use a stethoscope to auscultate the diesel engine cylinder at the noisiest speed. If there is strong noise accompanied by vibration, it can be diagnosed as bearing noise.

(2) The noise does not change during the fuel cut-off test, so you can change the throttle slowly. If the idle noise is clear, the noise is obvious at medium speed, and the noise decreases from disorder at high speed, it can be diagnosed as excessive axial clearance of camshaft or loose bearing.

Third, the valve leaks.

Phenomenon:

When a fault occurs, the diesel engine may be difficult to start, the exhaust pipe may emit black smoke, the fuel consumption may increase, and abnormal noise may occur.

engine maintenance

Reason:

(1) Air leakage is caused by abrasion, ablation and poor sealing between the valve and the valve seat ring.

(2) There is carbon deposit on the working face of the valve and valve seat ring, and the valve is not tightly closed and there is leakage.

(3) The gap between the valve and the valve guide is too large, and the valve stem shakes, resulting in irregular valve closing and air leakage.

(4) The valve stem is stuck or stuck in the valve guide, and the valve cannot move up and down.

(5) The valve spring loses elasticity or the spring breaks.

Diagnosis and elimination:

After troubleshooting the ignition system and fuel system, it is still impossible to determine the cylinder pressure when the fault occurs. The fault can be accurately determined by measuring the cylinder pressure or the vacuum degree of the intake manifold. When measuring cylinder pressure, the pressure of the cylinder with valve leakage is lower than that of other cylinders.

Fourthly, the liquid supports the column ring

Phenomenon:

When the diesel engine is running, the rhythmic noise is obvious at idle speed, and weakens or disappears above the medium speed.

Reason:

(1) The lubricating oil page of diesel engine is too high or too low, which causes the oil with bubbles to enter the hydraulic tappet, forming elastic gas and generating noise.

(2) The lubricating oil pressure is too low.

(3) The lubricating oil pump and filter are damaged or broken, and air is sucked into the lubricating oil.

(4) Hydraulic prop failure.

(5) Use inferior lubricating oil.

Diagnosis and elimination:

(1) Check the lubricating oil level, and add or replace it as appropriate, so that the oil quantity is in a normal state.

(2) Check whether the lubricating oil pressure is normal and whether the hydraulic support column is invalid.

Exclusion method:

Remove the oil pan, check the lubricating oil pump, filter and replace the lubricating oil; Remove and check the valve train, and replace the hydraulic prop or valve guide.