Analysis of the Causes Affecting the Seal Quality of Engine Cylinder Head

Analysis of the Causes Affecting the Seal Quality of Engine Cylinder Head

The sealing performance of Cylinder Head directly affects the technical condition of engine. In severe cases, the engine power drops sharply and even the work cannot be carried out. If the cylinder pad is damaged, the compression force of the engine cylinder is insufficient, and the speed is significantly reduced. Accompanied by exhaust pipe smoke (white smoke), bubble in the tank (and cooling water consumption too fast), water surface oil foam and other phenomena. Many operators do not know the cause of the Cylinder Head Gasket damage, only that the replacement of a new cylinder head gasket. As a result, the cylinder head gasket is constantly burning. Replacing engine cylinder pads is a matter of prudence. This is also a difficult job for maintenance technicians. If the cylinder head gasket is not used as required, or the cylinder head gasket is not assembled according to the correct method of operation, or is not properly inspected before assembly to find out the cause of damage, the sealing effect will certainly not be satisfactory. So, how to ensure the quality of the cylinder head seal? In the author's opinion, we must first find out the reasons affecting the sealing quality of cylinder head, and then take appropriate medicine to the case, in order to fundamentally solve the problem. This paper analyzes several common reasons affecting the sealing quality of cylinder head and the measures to be taken for reference.

First, the cylinder head gasket is not installed correctly
The cylinder head gasket is installed between the engine block and the cylinder head. Its function is to ensure the sealing of the combustion chamber and prevent the leakage of gas, cooling water and lubricating oil. Therefore, the use and installation of cylinder head gasket does not meet the requirements, which directly affects the sealing reliability of cylinder head and the life of cylinder head gasket.
In order to ensure the sealing quality, the selected cylinder head gasket must have the same specifications and thickness as the original cylinder head, the surface should be smooth, the edge must be tight, no scratches, depressions, folds, rust and other phenomena. Otherwise it will affect the sealing quality of the cylinder head.
Replacement of cylinder head gasket should be carried out during the cooling. Cylinder head has positive and negative points, the front is smooth, the reverse is rough, should pay attention to assembly. Due to the amount of projection on the cylinder mouth side (back side) of the cylinder head gasket, it will cause indentation deformation on the plane in contact with it. Therefore, when installing, roll surface (reverse) should face easy repair contact surface or hard surface (usually the cylinder head and cylinder body for cast iron, roll surface (reverse) should face the cylinder head; If the cylinder head is aluminum alloy, the cylinder is cast iron, the roll edge (back) should be toward the cylinder, and the positioning hole should be aligned with the positioning pin of the cylinder. For some high-strength, high-power turbocharged imported diesel engines, the use of pure metal cylinder head gaskets should be marked on one side (such as TOP or UP), and should face the cylinder head (can not be replaced by ordinary cylinder head gaskets). Cylinder head, oil road, waterway elastic reinforcement should be intact.
In addition, the repeated use of cylinder block gasket, due to reduced elasticity and deformation, its sealing performance and performance will also be affected. Therefore, in general, do not reuse cylinder head gaskets. The old cylinder head gasket was placed in waste oil and heated to 100°C for about 0.5 h before assembly. This can effectively expand the asbestos in the cylinder pad, restore its elastic properties, improve sealing performance and reliability.
Two, the cylinder head slight hammering
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 extend the head connection bolts, which causes the head to beat slightly with respect to the block. This slight beat will cause the cylinder head gasket relaxation and compression, accelerate the cylinder head gasket damage, affecting its sealing performance. Under normal circumstances, this tiny jump is so small that it amounts to almost nothing. Then, under normal circumstances, its impact on the cylinder seal performance is small, almost equal to zero. However, under abnormal conditions, the impact of this jump on the cylinder seal performance becomes apparent.