Why Yuchai Generator Make Abnormal Noise

Aug. 25, 2021

Any mechanical equipment make noises during operation, but sometimes users find that in addition to normal noises, there is some abnormal noises. For example, abnormal noises in the engine cylinders of Yuchai diesel generator sets can include: piston knocking, Piston pin knocking sound, piston top hitting cylinder head sound, piston top knocking sound, piston ring knocking sound, valve knocking sound and cylinder knocking sound, etc. So what's the matter with these abnormal noises when Yuchai generators are running? Let's analyze it together.



Why Does Yuchai Generator Make Abnormal Noise When It Is Running



1. The impact of the piston crown and the cylinder head

The abnormal sound of the piston top hitting the cylinder head is a continuous metal knocking sound, especially at high speeds. The source of the abnormal sound is on the upper part of the cylinder, the sound is solid and powerful, and the cylinder head vibrates. The main reasons are as follows.

(1) Crankshaft bearings, connecting rod bearings and piston pin holes are severely worn, and the fit clearance is seriously exceeded. At the moment when the piston stroke changes, the top of the piston hits the cylinder head under the action of inertial force.

(2) The distance from the center line of the piston pin hole to the top surface of the piston is greater than that of the original piston due to the mistaken installation of other pistons of similar specifications or inferior quality when replacing the piston.


2. Abnormal noise in the piston ring

The abnormal sound of the piston ring part mainly includes the metal percussion sound of the piston ring, the air leakage sound of the piston ring and the abnormal sound caused by excessive carbon deposit.

(1) The metal knocking sound of the piston ring. After the engine has been working for a long time, the cylinder wall is worn out, but the upper part of the cylinder wall and the piston ring are not in contact with the element geometry and size, which causes the cylinder wall to generate a step, if the old cylinder gasket is used Or the replacement of the new cylinder gasket is too thin, the working piston ring will collide with the cylinder wall steps, making a dull metal collision sound. If the engine speed increases, the abnormal noise will increase accordingly. In addition, if the piston ring is broken or the gap between the piston ring and the ring groove is too large, it will also cause a loud knocking sound.

(2) The sound of air leakage from the piston ring. The elastic force of the piston ring is weakened, the opening gap is too large or the openings overlap, and the cylinder wall is drawn with grooves, etc., which will cause the piston ring to leak air. The sound is a kind of "drinking" or "hissing" sound, and a "poofing" sound when severe air leakage occurs. The diagnosis method is to stop the engine when the water temperature of the engine reaches 80℃ or higher. At this time, inject a little fresh and clean oil into the cylinder, and restart the engine after shaking the crankshaft for a few times. If it occurs, it can be concluded that the piston ring is leaking.


(3) Abnormal sound of excessive carbon deposit. When there is too much carbon deposit, the abnormal noise from the cylinder is a sharp sound. Because the carbon deposit is red, the engine has symptoms of premature ignition, and it is not easy to stall. The formation of carbon deposits on the piston ring is mainly due to the lack of seal between the piston ring and the cylinder wall, the excessive opening gap, the reverse installation of the piston ring, and the overlap of the ring ports. The ring part burns, resulting in the formation of carbon deposits and even sticking to the piston ring, causing the piston ring to lose its elasticity and sealing effect. Generally, this fault can be eliminated after replacing the piston ring with a suitable specification.


The usual solution to the failure of diesel generator sets is to listen, watch, and check. The most effective and direct method to predicate the fault is by the sound of the machine which could be done by experienced technician who usually can judge whether the machine operate normally, and some minor faults can be eliminated in the bud through sound, and the occurrence of major faults of the unit can be avoided.


Please contact us if you have technical problem. Our company, Guangxi Dingbo Power Equipment Manufacturing Co., Ltd has been dealing in the field of design and production of diesel generator for more than ten years. As a reputable diesel generator manufacturer, we have a team of professional technicians and after-serve personnel who are ready to serve any time. You are welcomed to visit our website for more information or contact us by dingbo@dieselgeneratortech.com.  

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