How to judge the engine cylinder gasket ablation fault? What are the precautions for replacing the cylinder head gasket?2019-04-02
The most important type of gasket on the cylinder head gasket, its role is to ensure the seal between the cylinder block and the cylinder head joint surface to prevent air leakage, water leakage and oil leakage. It is usually made of thin metal sheet asbestos. Now it also uses pure metal gaskets. Due to the harsh working environment, it is required to be heat-resistant and corrosion-resistant, and has sufficient strength, elasticity and thermal conductivity to ensure a reliable seal.
Cylinder head ablation failure is relatively easy to diagnose. After the engine is started, a severe "beep, squeak" sound will be emitted from the damaged part of the cylinder head gasket. When the engine is severe, the exhaust gas can be seen to be discharged, and the hand can move along the cylinder head to feel the hot air. Water, oil or air bubbles emerge from the joint surface of the cylinder block. This is that the ablation part of the cylinder head is connected to the outside world. There is also a case where the air leakage is not visible outside, but the engine water temperature rises too fast, and the kettle is often opened. At the moment the engine is turned off, bubbles appear in the water tank. This is The ablation between the cylinder head gasket and the cooling water channel is a relatively hidden fault. We can also use a single-cylinder fire-breaking oil or measuring the cylinder pressure to diagnose. Generally, the cylinder pressure of the cylinder head ablation is obviously reduced. After the fire is cut off, the cylinder can be obviously not working or working poorly.
There are many reasons for the ablation of the cylinder head gasket. For example, the engine is working under heavy load for a long time or is often deflagrated. The engine heat is poor or the cooling system is faulty, causing the engine temperature to be too high. The cylinder head is suddenly deformed by heat and cold. The flatness is out of tolerance, the cylinder cap fastening bolts are loose, and the tightening of the cylinder head bolts is not operated according to the specified requirements. The torque does not meet the requirements or the torque is uneven, the cylinder gasket quality is not good, and so on.
After the cylinder head gasket is ablated, it must be replaced. The operation of disassembling the cylinder head is a labor-intensive and technically demanding maintenance operation, and must be operated in strict accordance with technical standards. When disassembling the cylinder head bolts, it must be carried out after the engine is completely cooled. When disassembling, follow the principle of “smoothly loosening from the two sides to the middle diagonal direction” to prevent the cylinder head from warping and deforming; then thoroughly clean the cylinder head and cylinder block Seal the surface and check the cylinder head and cylinder block sealing surface for deformation. The selected cylinder head gasket must be the original fittings that meet the requirements and are of reliable quality. Pay attention to the installation direction when installing.
The fastening of the cylinder head bolt is the most important part to ensure the quality of the cylinder head gasket. It directly affects the sealing quality of the cylinder head gasket and must be operated strictly in accordance with technical standards. First of all, we must thoroughly clean the debris and liquid in the bolt hole and blow it clean with compressed air; the cylinder head bolt is preferably replaced with a new one. Apply a little oil to the threaded part and the flange support surface before installation, from the middle to the sides. The cross-fastening is extended symmetrically, and the torque is tightened to the specified torque in 2 to 4 times, and the tightening is repeated when the engine is hot.
After installing the cylinder head, we also need to install the valve mechanism, such as the valve rocker arm, and the camshaft and other accessories such as timing belt or chain.