Causes and Repair Methods of Cylinder Gasket Failure

Engine cylinder head gasket burnout and compression system leakage are frequent failures. After the cylinder head gasket is burned, the working condition of the engine will be seriously deteriorated, and it may not work, and may also cause damage to some related parts or parts; during the compression and power stroke of the engine, the seal of the upper space of the piston must be kept intact. , must not leak. Combined with the symptoms of cylinder head gasket burnout and air leakage in the compression system, analyze and judge the causes of the failure symptoms, and point out the operation methods to prevent the occurrence of failures and effectively eliminate them.

First, Failure performance after the cylinder head gasket is damaged

Due to the different positions of the cylinder head gasket burning, the symptoms of failure are also different:

1. Blow-by gas between two adjacent cylinders

Under the premise of not turning on the decompression, crank the crankshaft and feel that the pressure of the two cylinders is not enough. When starting the engine, there is a phenomenon of black smoke, the engine speed drops significantly, and the power is insufficient.

2. Air leakage of cylinder head

The compressed high-pressure gas escapes into the bolt holes of the cylinder head or leaks out from the joint surface of the cylinder head and the body. There is light yellow foam at the air leakage. When the air leakage is serious, there will be a sound of "peeping", and sometimes it will be accompanied by water leakage or oil leakage. When disassembling and inspecting, you can see the corresponding cylinder head plane and its vicinity. There is obvious carbon deposits in the cylinder head bolt holes.

3. In the oil passage of gas oil

The high-pressure gas escapes into the lubricating oil passage that communicates between the engine block and the cylinder head. The temperature of the oil in the oil pan is always high when the engine is running, the oil viscosity becomes thinner, the pressure decreases, and the deterioration is fast.

4. High pressure gas enters the cooling water jacket

When the engine cooling water temperature is lower than 50 ℃, open the water tank cover, and you can see that there are obvious bubbles rising and emerging in the water tank, and at the same time, a large amount of hot air is emitted from the water tank mouth. As the engine temperature gradually increases, The heat emanating from the mouth of the water tank is also increasing. In this case, if the overflow pipe of the water tank is blocked, and the water tank is filled with water to the cover, the phenomenon of bubbles rising up will be more obvious, and in severe cases, the phenomenon like boiling will occur.

5. The engine cylinder and the cooling water jacket or the lubricating oil channel are channeled through

There will be yellow-black oil bubbles floating on the upper surface of the cooling water in the water tank, or there will be water in the oil in the oil pan.

Second, Analysis of the reasons for the damaged cylinder head gasket

1. Elongation or loosening of cylinder head bolts and nuts

Due to the extrusion deformation of the joint surface of the cylinder head and the engine body, the compression deformation of the cylinder head gasket, the accidental overload caused by the pressure of the high-pressure gas to the cylinder head bolts and nuts, the cylinder head bolts are not screwed deeply enough, and the microscopic unevenness of the thread surface is compressed. The flatness and the necking of the bolts due to excessive torque can cause the cylinder head bolts and nuts to be elongated or loosened, resulting in insufficient pressure on the joint surface of the cylinder head and the engine body and uneven pressure everywhere, resulting in high temperature and high pressure gas from local. The lower pressure part pops out and burns the cylinder head gasket.

2. Deformation of the joint surface of the cylinder head and the engine body

If the two joint surfaces are deformed, the cylinder head gasket cannot be guaranteed to be evenly compressed, thus causing air leakage and causing the cylinder head gasket to burn, which is also the main reason for the cylinder head burn.

3. The installation does not meet the technical requirements

During installation, the joint surface of the cylinder head gasket is not clean, the sequence of tightening the bolts and nuts of the cylinder head is incorrect, the torque is not large enough or uneven, and the size of the upper end face of each cylinder liner above the upper plane of the engine body is not enough or not equal, resulting in air leakage and burning. cylinder head gasket.

4. Engine overheating

The engine cooling system does not work properly, the oil supply time is too late, and the long-term overload work will cause the engine to overheat, especially in the part between the intake and exhaust valve seat of the cylinder head and the outlet of the vortex chamber passage. As a result, the cylinder head gasket loses its original elasticity and becomes brittle, and finally burns out.

5. The quality of the cylinder head gasket itself is unqualified

Such as uneven thickness, uneven roll mouth, insufficient elasticity, poor material, uneven surface, etc., or the cylinder head gasket is damaged by careless disassembly and assembly, it is easy to cause the cylinder head gasket to burn.

Third,Methods to prevent cylinder head gasket from being burned and damaged

1. Strictly check the warpage of the two joint surfaces of the cylinder head and the engine body before installation.

2. Check whether the protruding height of the upper end face of each cylinder liner on the upper plane of the engine body is high enough and uniform.

3. Check whether the quality of the cylinder head gasket is qualified.

4. During the installation process, evenly tighten the bolts and nuts as required, and reach the specified torque.

5. After replacing the new cylinder head gasket, after the engine works for 10 to 15 hours, check and tighten the cylinder head bolts and nuts one by one according to the specified order and torque. After the engine works for 240-250 hours, the tightness of the cylinder head bolts and nuts should be checked once, and tightened in time if they are loose.

6. Before installation, apply special graphite paste on both sides of the cylinder head gasket. The thickness of the coating is between 0.03 and 0.05 mm. disassemble. Applying a thin layer of butter on both sides of the cylinder head gasket can also increase the tightness after installation, but it should not be worked for a long time, otherwise the cylinder head gasket and the joint surface will be tightly bonded and easily damaged during disassembly.

7. Evenly place a thin layer of asbestos wire or add a thin copper sheet with a thickness of less than or equal to 0.2 mm in the parts where the cylinder head gasket often burns to make the cushioned parts more tightly bonded to prevent the cylinder head gasket from burning. Damage

Summarize:

The cylinder head gasket parts on the engine often work under severe conditions of high temperature, high pressure and high-speed relative motion. Therefore, the cylinder head gasket and related parts are easy to burn and cause rapid mechanical wear.

In order to make the engine always work in a good technical state and prolong its service life, it must be used reasonably and properly maintained. When there are signs of failure, it is necessary to quickly find out the cause of the failure and study the solution. The fault will be eliminated after the solution.