Industry News

Common Failures of Cylinder Head Gasket Destruction

2021-09-30
Common failures of cylinder head gasket destruction
The ablation of the cylinder sealing ring and the reduction of system software gas leakage are common faults that often occur. After the cylinder head gasket is burned, the diesel engine's working conditions will be severely changed. If it is unable to work, it will cause the reduction of the relevant components and positions. Make sure that the inner space of the upper end of the piston rod is tightly sealed and there is no air leakage.
Combining the symptoms of cylinder gasket damage and reducing system software leaks, analyzes the causes of common failure signs, and emphasizes the operation steps to avoid common failures and reasonable failure detection.
1. The main manifestations of common failures after the cylinder head gasket is damaged
According to the ablation of the cylinder head gasket, the common fault signs of the displayed information are also different.
a. Blow-by in the middle of the adjacent two cylinders
If the crankshaft of the engine is not shaken while the pressure is relaxed, the working pressure of the two cylinders will be insufficient. When the diesel engine is started, the exhaust pipe will emit black smoke, and the speed of the car will be significantly reduced and the driving force will be insufficient.
b. Cylinder head leaks
The reduced high pressure gas enters the anchor bolt hole of the cylinder head or leaks from the fusion surface of the cylinder head and the human body. Light yellow foam appears at the gas leak. When the gas leak is serious, there will be a "neighboring" sound. Sometimes with water or oil seepage, it will dissolve the matching head plan view and the surrounding head and anchor bolt holes during the inspection. Significant carbon deposition can be seen inside.
c. Gas car oil is strung into the oil passage
The high-pressure gas is cascaded into the lubricating oil passage of the diesel engine that communicates with the cylinder head. The oil temperature of the oil pan is always high when the diesel engine is running, the oil viscosity becomes soft, the working pressure is reduced, and the mildew is accelerated. The oil passed to the lubrication and gas distribution mechanism at the upper end of the cylinder head significantly contains vapor bubbles.
c. High pressure gas is connected to the cooling circulating water jacket
When the temperature of the cooling circulating water of the diesel engine is less than 50℃, open the fuel cap, and there will be a significant increase of air bubbles in the car fuel tank. In addition, a lot of heat flow is released from the car fuel tank port. As the temperature of the diesel engine rises, the car fuel tank port releases The heat flow also slowly increased. In this situation, if the overflowing water pipe of the water storage tank is plugged and the water tank is filled with oil and water to the outlet of the cover, the bubble rising will be more noticeable. If it is more serious, it will appear as if it is boiling.
d. The diesel engine cylinder and the cooling circulating water jacket or the safe passage of grease pass through
The foamed plastic with light yellow oil floating on the cooling circulating water in the water storage tank and the oil in the oil pan have significant water. These two types of air leakage conditions are more serious, and the exhaust pipe will be stained with water and oil.
2. The root cause of the damaged cylinder head gasket
a. Lengthening or loosening of cylinder head anchor bolts and nuts
The shrinking deformation of the joint surface between the cylinder head and the engine oil pan, the shrinking deformation of the cylinder head gasket, and the working pressure of the high pressure gas cause inadvertent load on the cylinder head anchor bolts and nuts. The cylinder head anchor bolts are not screwed deep enough. , The external economic convexity of the surface of the external thread is becoming more and more smooth, the torque is too large, the anchor bolts are getting more and more necked, etc. Because of the expansion and loosening of the cylinder head bolts and nuts, the joint surface of the cylinder head and the engine oil pan works. Insufficient pressure and uneven working pressure of various parts, such as ultra-high pressure steam, fly out from some areas with low working pressure, and burn the cylinder head gasket.
b. Deformation of the joint surface of the cylinder head and the body of the diesel engine
After the two joint surfaces are deformed, it is impossible to ensure that the cylinder head gasket is evenly clamped. The ablation of the cylinder head gasket caused by gas leakage is the key reason for the cylinder head gasket ablation.
c. The installation does not meet the technical standards
The joint surface of the cylinder liner is not tidy during installation, the sequence of tightening the cylinder head bolts and nuts is incorrect, the torque is insufficient or uneven, the inner hole of each cylinder liner is higher than the upper surface of the engine oil pan. The specifications are insufficient or uneven, Gas leakage caused cylinder liner to burn
d, diesel engine over temperature
The refrigeration system of the diesel engine is working abnormally, the oil supply time is too slow, and the long-term load operation causes the diesel engine to over-temperature, especially the temperature rise between the cylinder head suction automatic exhaust valve seat and the opening of the scroll chamber , Under the effect of high temperature, the cylinder head gasket loses its original ductility and becomes brittle, and is finally damaged.
e. The quality of the cylinder head gasket itself is not good enough
If the thickness is uneven, the roll mouth is not flat, the ductility is not enough, the raw material is not good, the surface is uneven, or the cylinder head gasket is damaged during disassembly, it is very easy to cause the cylinder head gasket to ablate.
3. Ways to avoid ablation and damage to the cylinder head gasket
a. Before installation, please strictly check the expansion and contraction of the joint surfaces of the cylinder head and the diesel engine.
b. Check whether the prominent aspect ratio of the inner hole of each cylinder liner on the main plan view of the diesel engine is sufficiently high and well-proportioned.
c. Check whether the quality of the cylinder head gasket meets the standard.
d. During the whole installation process, tighten the bolts and nuts evenly according to the regulations and achieve the required torque.
After replacing the cylinder head gasket, the cylinder head bolts and nuts should be checked and tightened regularly in sequence and torque after 10-15 hours of diesel engine operation. After that, the tightness of the cylinder head bolts and nuts should be checked every 240 to 250 hours during the diesel engine's operation, and they should be tightened immediately when they become loose.
e. Before installation, apply special high-purity graphite paste on both sides of the cylinder gasket. The thickness of the coating is 0.03~0.05mm. In addition to improving the air tightness test, it is beneficial to the disassembly and assembly of the next cylinder head and cylinder gasket. Even if the lubricating grease is wiped thinly on both sides of the cylinder head gasket, the air tightness test after installation will be improved, but if it does not work for a long time, the cylinder head gasket and the joint surface will be inseparably touched, and it is very easy to be damaged during disassembly.
f. Add a thin layer of asbestos thread in the area where the gasket is often ignited. A layer of copper with a moderate thickness less than or equivalent to 0.2mm should be used to make the gasket connector more inseparable to avoid the gasket from igniting.
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