The valve is an important part of the engine. The function of the valve is to specifically input air into the engine and exhaust the exhaust gas after combustion. From the structure of the engine, it is divided into an inlet valve and an exhaust valve. The role of the intake valve is to suck air into the engine and mix it with fuel for combustion; the role of the exhaust valve is to exhaust and dissipate the exhaust gas after combustion. If we encounter abnormal engine valve noise in daily vehicles, we can judge the fault according to these methods.

　　Valve abnormal noise:

　　When the engine is idling, a continuous, rhythmic "click, click, click" (at the valve foot) or "click, click, click" (at the valve seat) metal tapping sound; the sound also increases when the speed increases With the increase, the sound does not decrease when the temperature changes and the single-cylinder fire is cut off; if there are several valves, the sound appears chaotic. The valve foot sound and the valve seating sound are collectively called the valve sound.

　　Causes of abnormal valve noise

　　1.The valve stem end and the adjustment screw or rocker arm are worn or improperly adjusted, causing the valve clearance to be too large, causing the side valve lifter end to collide with the adjustment screw, or the rocker head of the overhead valve hitting the valve end .

　　2. The cam wears excessively, and the tappet generates runout during operation.

　　3. The valve spring seat comes off.

　　4. The valve tappet fixing nut is loose or the end face of the adjustment bolt is uneven.

　　5. Excessive carbon deposits in the valve guides bit the valve.

　　Performance characteristics of radon valve noise

　　1. When the engine is idling, it makes a rhythmic "click, click" sound.

　　2. As the engine speed increases, the sound also increases. When the speed is above medium speed, the sound becomes fuzzy and noisy.

　　3. There is no change in sound when the engine temperature changes or a misfire test is performed.

　　Valve abnormal sound judgment method

　　1. During the inspection of the valve cover, the sound changes with the change of the engine speed. At the same time, there is no change in the sound of the engine temperature or the fire test. It can be determined as the valve sound.

　　2. Run the engine at idle speed and insert the thickness gauge into the gap between the valve end and the tappet. When a certain valve gap is inserted, the sound weakens or disappears. It can be determined that the valve gap is too large and sounds; Later, the sound was reduced but not disappeared, and then the valve lever was pried with a screwdriver. If the sound was eliminated, it was determined that the valve stem and the duct were excessively worn and sounded.

　　Valve abnormal noise troubleshooting:

　　Valve leak

　　The valve leak sound is outside the valve, which is more obvious at high load and low speed. The sound increases with the increase of load. The main reason is that when the valve seat is reamed, the valve seat is skewed due to improper operation or excessive wear of the valve guide bore. Or the valve clearance is small, which causes the valve ablation to cause the valve to close improperly and cause air leakage.

　　Handling method: Remove the cylinder head, grind the valve, check the spring force of the valve spring, and readjust the valve clearance.

　　Throttle valve knock

　　When the engine is idling, a continuous knocking sound occurs between the tail end of the valve rod and its driving parts, which increases with the increase of the speed, and there is no change in the sound when the engine temperature changes or the flame is interrupted.

　　Main reasons:

　　1. There is a change in the adjusted valve clearance (inadequate locking, wear between the valve stem and the driving parts), and the valve is not adjusted properly.

　　2. The valve adjusting screw is worn, the lock nut is loose, and the valve clearance is too large or inconsistent.

　　3. The valve spring seat is worn and grooved, and the valve stem and the duct are worn too much.

　　Handling method: readjust the valve clearance, if the lock nut on the adjustment screw is loose, it should be locked, and the worn out parts should be replaced.

　　1. The valve spring is broken and should be replaced.

　　2, the valve seat rings, the seat ring falls off

　　The surface of the valve seat is rough, the machining accuracy is unqualified, the interference of the seat is not properly selected, which results in looseness, the material is deformed excessively when exposed to heat, or the valve seat mounting process is not satisfactory.

　　Treatment method: Reassemble the valve seat according to the requirements of the assembly process. The upper end face should be flush with the body plane, and the higher part should be repaired.