The sealing performance of the cylinder head directly affects the technical condition of the engine. When it is serious, the power of the engine drops sharply, and even the work cannot be performed. For example, when the cylinder mat is damaged, the engine cylinder's compression force is insufficient, and its rotation speed is obviously reduced. It is accompanied by smoke from the exhaust pipe (white smoke), air bubbles in the tank (and cooling water consumption is too fast), and water surface Organic oil foam and other phenomena. Many operators do not know the cause of the cylinder head gasket damage, but only know that the new cylinder head gasket is replaced. As a result, the cylinder head gasket is continuously burned. Replacing the engine cylinder pad is a matter of caution. It is also a difficult job for maintenance technicians. If the cylinder head gasket is not used as required, or if the cylinder head gasket is not assembled in accordance with the correct method of operation or the proper inspection is not made before the assembly and the cause of the damage is found out, the effect of the sealing will certainly not be satisfactory. So, how to ensure the quality of the cylinder head seal? The author believes that we must first find out the reasons that affect the quality of the cylinder head seal, and then the right medicine, in order to solve the fundamental problem. This article analyzes several common causes that affect the quality of cylinder head seals and some measures that should be taken for reference by their counterparts.
I. Incorrect use and installation of cylinder head gasket
The cylinder head gasket is installed between the cylinder block of the engine and the cylinder head. Its role is to ensure the sealing of the combustion chamber and prevent the leakage of gas, cooling water and lubrication oil. Therefore, the use and installation of cylinder head gaskets do not meet the requirements, which directly affects the sealing reliability of cylinder heads and the life of cylinder head gaskets.
In order to ensure the quality of the seal, the selected cylinder head gasket must have the same specifications and thickness as the original cylinder, the surface should be flat, the edging must be tightly attached, and there should be no scratches, depressions, folds, and rust. Otherwise, it will affect the seal quality of the cylinder head.
When replacing the cylinder head gasket, it should be carried out during the cold machine. The cylinder head has the positive and negative points, the front surface is relatively smooth, the reverse surface is rough, and attention should be paid when assembling. Due to the projected amount of one side (reverse side) of the cylinder head gasket cylinder port, the indentation deformation will be caused to the plane in contact with it. Therefore, when installing, the curled side (reverse side) should face the easy-to-repair contact surface or hard surface (normally the cylinder head and cylinder block are cast iron, the curling (reverse) should face the cylinder head; if the cylinder head is aluminum alloy, The cylinder body is cast iron, and the curling (reverse surface) should face toward the cylinder block.), and the positioning hole should be aligned with the positioning pin of the cylinder block. For some high-strength, high-power turbocharged imported diesel engines, the use of pure metal cylinder head gaskets should be marked with a mark (such as TOP or UP) on one side and should face the cylinder head (not to be replaced by ordinary cylinder head gaskets). The elastic ribs at the cylinder port, oil passageway, and waterway must be intact.
In addition, the re-use of the cylinder gasket, due to the reduction of elasticity and deformation, its sealing performance and performance will be affected. Therefore, in general, do not reuse the cylinder head gasket. To reuse the old cylinder head gasket, put it in waste oil and heat it to 100 °C for about 0.5 h before assembly. This can effectively expand the asbestos in the cylinder pad, restore its elastic properties, and improve the sealing performance and use reliability.
Second, the cylinder head slightly beat
The slight beating of the cylinder head is the result of the cylinder head trying to separate from the cylinder under compression and combustion pressure. These pressures lengthen the cylinder head attachment bolts, thus causing a slight run-out of the cylinder head relative to the cylinder block. This slight jump will cause the cylinder head gasket to relax and compress, which will accelerate the damage of the cylinder head gasket and affect its sealing performance. Under normal circumstances, this slight jump is very small, almost equal to zero. Then, under normal circumstances, its impact on the cylinder sealing performance is also very small, almost equal to zero. However, under abnormal conditions, the effect of this jump on the sealing performance of the cylinder becomes apparent.
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