Reasons why the engine cylinder head is not tightly sealed (on)

Nov. 25, 2019

The sealing performance of the cylinder head has a great influence on the technical condition of the engine. When the cylinder head is not tightly sealed, the cylinder will be leaked, resulting in insufficient cylinder compression pressure, temperature reduction and air quality reduction. When the cylinder leaks seriously, the engine power will be significantly reduced or even unable to work. Therefore, if there is a power drop failure during engine operation, in addition to finding the cause of the failure that affects the engine power drop, it is also necessary to check whether the cylinder head sealing performance is good. The following hyundai cylinder head factory analyze the main reasons affecting the sealing performance of the engine cylinder head for reference.

1. Cylinder head is used and installed incorrectly

The cylinder head gasket is installed between the engine cylinder block and the cylinder head. Its function is to ensure the sealing of the combustion chamber and prevent leakage of gas, cooling water and lubricating oil. Therefore, the use and installation of the cylinder head gasket is not satisfactory, which directly affects the sealing reliability of the cylinder head and the service life of the cylinder head gasket.

In order to ensure the quality of the seal, the selected cylinder head gasket must be the same size and thickness as the original cylinder. The surface should be flat, the edging fits firmly, and there are no scratches, dents, wrinkles and rust. Otherwise, it will affect the quality of the seal of the custom cylinder head.

2. Slightly beat of the cylinder head

The slight runout of the cylinder head is the result of the cylinder head trying to separate from the cylinder under compression and combustion pressure. These pressures elongate the cylinder head attachment bolts, thus causing the cylinder head to have a slight bounce relative to the cylinder block. This slight jump will cause the cylinder head gasket to relax and compress, thereby accelerating the damage of the cylinder head gasket and affecting its sealing performance.

Cylinder Head

Cylinder Head

3. The cylinder head connecting bolt does not reach the specified torque value.

If the cylinder head connecting bolts are not tightened to the specified torque value, the cylinder head wear caused by this slight jump will occur faster and more severely. If the connecting bolt is too loose, the amount of runout of the cylinder head relative to the cylinder will increase. If the connecting bolt is tightened too much, the force on the connecting bolt will exceed its yield strength limit, causing the connecting bolt to extend beyond its design tolerance, which will also increase the runout of the cylinder head. Accelerate the wear of the cylinder head gasket. By using the correct torque ratings and tightening the connecting bolts in the correct order, the cylinder head relative to the cylinder can be minimized to ensure the seal quality of the cylinder head.

4. Cylinder head or cylinder flatness is too large

Warpage and twisting are common problems in casting cylinder heads and are the main cause of repeated burning of cylinder head gaskets. In particular, the aluminum alloy cylinder head performs more prominently because the aluminum alloy material has a high heat transfer efficiency, and the cylinder head is smaller and thinner than the cylinder block, and the temperature of the aluminum alloy cylinder head rises rapidly. . When the cylinder head is deformed, it will not be tightly engaged with the plane of the cylinder block, and the sealing quality of the cylinder will be lowered, causing air leakage and burning of the cylinder head gasket, thereby further deteriorating the sealing quality of the cylinder. If the cylinder head is severely warped, it must be replaced.