The good or bad sealing performance of the cylinder head has a great impact on the technical condition of the engine. When the cylinder head seal is not tight, it will make the cylinder leakage, resulting in insufficient cylinder compression pressure, lower temperature and reduced air quality. When the cylinder air leakage is serious, the engine power will be significantly reduced, or even unable to work. Therefore, in the engine work if there is a power failure, in addition to find the engine power decline in the relevant causes of the failure, but also to check whether the cylinder head sealing performance is good. The following editor will affect the engine cylinder head sealing performance of the main reasons for analysis, for reference.
1. The use of the cylinder gasket and installation is not correct
Cylinder gasket is installed in the engine cylinder block and cylinder head, its role is to ensure that the seal of the combustion chamber, to prevent gas, cooling water and lubricating oil leakage. Therefore, the use of the cylinder gasket and installation is not in accordance with the requirements, it directly affects the reliability of the cylinder head seal and cylinder gasket life.
In order to ensure the quality of sealing, the selection of the cylinder gasket must be matched with the original cylinder specifications and thickness of the same, the surface should be flat, the edge of the package fit firmly, and no scratches, depressions, wrinkles, as well as rust stains and other phenomena. Otherwise, it will affect the sealing quality of the cylinder head.
2. Slight jumping of the cylinder head
Cylinder head of the slight jump is in the compression and combustion pressure, the cylinder head is trying to separate from the cylinder block caused by the results. These pressures elongate the cylinder head attachment bolts, thus causing the cylinder head to have a slight runout relative to the block. This slight jump will make the cylinder head gasket relaxation and compression process, thus accelerating the cylinder head gasket damage, affecting its sealing performance.
3. Cylinder head connecting bolt does not reach the specified torque value
If the cylinder head connecting bolt is not tightened to the specified torque value, then the cylinder gasket wear caused by this slight jump will occur faster and more serious. If the connecting bolts are too loose, this will result in an increase in the amount of runout of the cylinder head relative to the cylinder block. If the connecting bolt is over-tightened, the force on the connecting bolt exceeds its yield strength limit, which causes the connecting bolt to elongate beyond its design tolerance, which also causes increased runout of the cylinder head and accelerated wear of the cylinder head gasket. Use the correct torque value, and in accordance with the correct order to tighten the connecting bolts, you can make the cylinder head relative to the cylinder block runout is reduced to a minimum, so as to ensure the sealing quality of the cylinder head.
4. Cylinder head or block plane is too large
Warping and twisting is the cylinder head is often a problem, but also caused by the cylinder gasket repeatedly burned the main reason. Especially the aluminium alloy cylinder head is more prominent, this is because the aluminium alloy material has a high heat conduction efficiency, while the cylinder head and the cylinder block compared to the smaller and thinner, aluminium alloy cylinder head temperature rises quickly. When the cylinder head deformation, it and the cylinder block plane joint will not be tight, the cylinder sealing quality is reduced, resulting in air leakage and burned cylinder gasket, which further deteriorates the sealing quality of the cylinder. If the cylinder head appears serious warping deformation, it must be replaced.
5. Uneven cooling of the cylinder surface
Uneven cooling of the cylinder surface will form local hot spots. Localised hot spots can lead to excessive expansion of the metal in small areas of the cylinder head or cylinder block, and this expansion can cause the cylinder head gasket to be squeezed and damaged. Damage to the cylinder gasket leads to leakage, corrosion and eventually burn-through.
If the cylinder gasket is replaced before the cause of the localised hotspot has been found, this will not help as the replacement gasket will still end up being burnt through. Localised hot spots can also lead to additional internal stresses in the cylinder head itself, with the result that the cylinder head cracks. Localised hot spots can also have serious negative effects if the operating temperature exceeds normal temperatures. Any overheating can lead to permanent distortion of the cylinder block cast iron parts.
6. Additives in the coolant related issues
When coolant is added to the coolant, there is a risk of air bubbles. Air bubbles in the cooling system can lead to cylinder head gasket failure. When there are air bubbles in the cooling system, the coolant will not be able to circulate properly in the system, so the engine will not be cooled uniformly, and local hot spots will occur, causing damage to the cylinder gasket and leading to poor sealing. Therefore, in order to be able to achieve uniform cooling of the engine, when adding coolant, the air must be discharged from the engine.
Some drivers use antifreeze in the winter, summer, switch to water, that is economical. In fact, this is a lot of trouble, because the minerals in the water is easy to produce scale and sticky floating in the water jacket, radiator and water temperature sensors, so that the engine temperature control is out of calibration and lead to overheating, and even cause the engine cylinder gasket punch bad, the cylinder head warping deformation, pulling the cylinder and burning tiles and other faults. Therefore, in the summer should also use antifreeze.
7. Diesel engine maintenance, assembly quality is poor
Engine maintenance and assembly quality is poor, is the main cause of the engine cylinder head sealing quality, but also cause the main factors of cylinder gasket burnout. For this reason, when repairing and assembling the engine, it is necessary to do it in strict accordance with the relevant requirements, and it is necessary to disassemble and assemble the cylinder head correctly.
When disassembling the cylinder head, it should be carried out in the cold state, and it is strictly prohibited to disassemble it in the hot state to prevent the cylinder head from warping and deformation. Disassembly should be symmetrical from both sides to the middle of the gradual loosening in several times. If the cylinder head and the cylinder block combination of solid removal difficulties, it is strictly prohibited to use metal objects knocking or sharp hard objects embedded in the mouth of the slit hard pry (effective method is to use the starter to drive the crankshaft rotating or rotating the crankshaft rotation, relying on the high-pressure gas generated in the cylinder will be the top of the open), in order to prevent scratching the cylinder block and the cylinder head of the joint surface or damage to the cylinder gasket.
In the assembly of the cylinder head, first of all, to remove the cylinder head and cylinder mating surface and the cylinder block bolt holes in the oil, charcoal, rust and other impurities, and blow clean with high-pressure gas. So as not to produce insufficient compression force of the bolt on the cylinder head. When tightening the cylinder head bolts, it should be symmetrically tightened 3-4 times from the middle to both sides, and the last time to reach the specified torque, and error ≯ 2%, for cast iron cylinder head in the warm-up temperature of 80 ℃, it should be re-torqued according to the specified torque to re-tighten the connecting bolts. For bimetallic engine, it should be in the engine after cooling, and then re-tighten the operation.
8. The selection of inappropriate fuel
Due to different types of structure of diesel engines, the cetane number of diesel fuel has different requirements. If the choice of fuel does not meet the requirements, not only will cause economy and power down, but also cause a lot of diesel engine carbon or abnormal combustion, resulting in high local temperature of the body, resulting in the cylinder gasket and the body of the ablation, so that the sealing performance of the cylinder head down. Therefore, the diesel engine diesel cetane number selection must meet the requirements of the use of regulations.
9. Improper use of diesel engines
Some engineers are afraid of engine stalling, so in the start of the engine, always continuous throttle, or when the engine is started to let the engine run at high speeds, in order to maintain the engine's working condition; in the process of travelling, often out of gear stalling skidding, and then gear forced to start the engine. In this case, the engine not only increases the wear and tear of the engine, but also make the pressure in the cylinder rises sharply, it is very easy to wash out the cylinder gasket, resulting in a decline in sealing performance. In addition, the engine is often overloaded work (or ignition too early), a long time shock combustion, resulting in local pressure and temperature inside the cylinder is too high, this time also damage the cylinder gasket, so that the sealing performance decline.
Post time: Jan-03-2025