First, the causes of cylinder gasket burning.
1, uneven tightness of cylinder head nut (bolt) leads to burning of cylinder gasket.
A. In use, the nuts (bolts) of the cylinder head are not checked and tightened regularly, and individual nuts (bolts) of the cylinder head are loose, so that the cylinder head cannot be pressed evenly on the cylinder body.
B. When tightening the cylinder head nuts (bolts), first tighten the middle two rows of nuts, and then tighten them alternately from the middle to the left. Otherwise, the tightness of nuts (bolts) will be uneven, and the cylinder gasket will not be evenly clamped between the cylinder block and the cylinder head.
C, when tightening the cylinder head nut (bolt), use a torque wrench. For convenience, some maintenance workers use ordinary wrenches to tighten, resulting in uneven torque. Some bolts have too large torque, and some bolts have too small torque, resulting in the cylinder head not being evenly pressed on the cylinder block.
D, cylinder head nut (bolt) tightening torque exceeds the specified value is too large, cylinder head cracks. The cylinder head bolt and the screw hole slide and deform, or the bolt is extended, and the screw hole of the machine body protrudes, resulting in a loose seal between the cylinder head and the machine body.
As a result, the pressure on the joint surface between the cylinder block and the cylinder head is insufficient, and the sealing performance of the joint surface is not good. High temperature and high pressure gas rushes out of the gap with a small local torque, which burns the cylinder gasket.
2. The uneven joint surface between the cylinder head and the engine body causes the cylinder gasket to burn.
A, when repairing or replacing parts, do not pay attention to the inspection, so that the cylinder head or the body joint surface warps, or has ablation, corrosion, pits, pits, etc. , can not be repaired and polished in time, so that the flatness of the bottom surface of the cylinder head or the top surface of the engine body exceeds the specified value.
B, when replacing the pre-combustion chamber or vortex chamber insert, the insert does not meet the technical requirements. When the insert is too thick and protrudes from the plane of the cylinder head, the cylinder head, cylinder gasket and cylinder liner cannot be pressed evenly; When the insert is too thin and below the plane of the cylinder head, gas will escape from the insert.
C, cylinder liner shoulder protruding from the plane height of the machine body is improper. If the protrusion is too high, the shoulder of the cylinder liner will hold the cylinder head, so that the cylinder pad cannot be pressed up; The plane value of the protruding cylinder block is too small or no protruding amount, even lower than the plane of the cylinder block, so that the cylinder head can not press the cylinder liner, the cylinder gasket is not tightly pressed, and the seal is not good.
D, multi-cylinder diesel engine, the height difference of the upper end of the cylinder liner shoulder protruding from the cylinder plane is inconsistent, and the cylinder liner with excessive protrusion will hold the cylinder head against it, resulting in the cylinder gasket not being pressed tightly.
The above situation leads to the failure of the cylinder gasket, which makes the cylinder sealing worse, and the high-temperature gas will escape from the gap, thus burning the cylinder gasket.
3. The cylinder gasket was burned due to improper use and assembly.
A. The cylinder gasket has been used for a long time. After repeated disassembly and assembly, the cylinder pad loses its elasticity. If it is reused without treatment or replacement, it will not play a good sealing role.
B carbon deposit, dirt, rust and convex hull on the joint surfaces of cylinder head, cylinder gasket and engine body are not carefully removed during installation, resulting in gaps between the joint surfaces after installation.
C. During installation, there is a single-sided flanging or curling on the cylinder pad, and the flanging or curling side is wrongly turned to the plane of the cylinder block, so gas can easily rush into the cylinder pad from the flanging position.
D, when installing, add butter to the plane of the cylinder pad, or directly soak the cylinder pad in diesel oil, and then install it after taking it out.
The above conditions and reasons are easy to burn the cylinder gasket.
4, diesel engine temperature is too high, resulting in burning cylinder gasket.
A, the compression ratio is too high or the compression gap is too small, so that the pressure at the end of compression is too high and the temperature generated during expansion combustion is too high.
B, the fuel supply advance angle is too small or too large, resulting in the high temperature of the diesel engine, heat can not be transferred in time, resulting in overheating of the cylinder head and cylinder block.
C, gas distribution phase is wrong; The air intake or exhaust system is blocked, resulting in insufficient air intake and unclean exhaust; Poor lubrication of cooperative moving parts; The failure of cooling system and poor heat dissipation effect are all the reasons that lead to overheating of diesel engine when it works.
D, the locomotive is often overloaded or the diesel engine is overloaded for a long time, which leads to the high temperature of the diesel engine due to overload.
As a result, the cylinder gasket is subjected to the long-term effect of high temperature, and the asbestos material deteriorates and hardens, and gradually loses its elasticity and is burned.
5. The cylinder gasket products were burned due to poor manufacturing quality.
A, the quality of the material used to manufacture the cylinder gasket is too poor, the elasticity is insufficient, and it is not resistant to high temperature, so it cannot meet the sealing requirements of the joint surface between the cylinder head and the cylinder block.
B, due to poor processing technology, the manufactured cylinder gasket is irregular, the flanging is not tight, and the thickness of asbestos paper in the metal sheath is uneven.
C the position, distance and geometry of the manufactured cylinder gasket hole do not meet the technical requirements, such as the wrong position of the cylinder gasket bolt hole, the wrong position of the cylinder liner hole and the wrong position of the cylinder gasket water passage hole.
In the above situation, even if the cylinder gasket can barely be installed, there will be ups and downs, the pressure will not be tight, and the pressure will not be in place, resulting in poor sealing of the cylinder head and cylinder block, and the cylinder gasket will be burned by the impact of high temperature gas.
Second, the cylinder pad combustion detection method
Use cylinder pressure gauge to detect the compression pressure of two adjacent cylinders of the engine. If they are all very low, it is usually that the cylinder gasket is not well sealed. Then carry out the following specific tests:
1. Check the tightness of cylinder gasket with rubber hose.
Start the engine, put one end of the rubber hose close to the ear, and look for the other end along the joint between the cylinder head and the cylinder block that may be poorly sealed. If the cylinder gasket is poorly sealed, you can clearly hear the deflation sound at the air leakage place.
2. Check the tightness of cylinder gasket by observing the splash of radiator.
Open the radiator cover, let the engine run at idle speed, observe the radiator coolant filler, and quickly press the accelerator pedal to the bottom. If bubbles gush from the coolant during sudden acceleration, it means that the cylinder gasket is poorly sealed. The more bubbles, the more serious the air leakage. In severe cases, the radiator port will splash when idling.
3. Use the exhaust gas analyzer to test the tightness of the cylinder gasket.
The coolant filler of some engine radiators is under the iron plate, so it is impossible to see bubbles. You can open the radiator cover and put the probe of the exhaust gas analyzer on the opened radiator cover to avoid contact with the coolant. If HC can be detected in the process of rapid acceleration, it means that the cylinder gasket is poorly sealed.
4. The air leakage of the cylinder gasket will cause the engine temperature to be too high and the power to drop, so it should be replaced in time, otherwise it will easily damage the cylinder head, cause the cylinder head to be scrapped, and cause the coolant to enter the combustion chamber.
III. Prevention of Cylinder Pad Burning
1. Dismantle the cylinder head in a cold state, and it is forbidden to disassemble it in a hot engine to prevent the cylinder head from warping and deformation. When disassembling, loosen it symmetrically from both sides to the middle, and repeat it several times. When the cylinder head is firmly combined with the cylinder block, if it is difficult to remove the cylinder head, it is forbidden to knock the cylinder head with a metal object or wedge it into the seam with a sharp hard object, so as not to scratch the joint surface of the cylinder block and the cylinder head or damage the cylinder pad.
2. When installing the cylinder gasket, first check whether the cylinder head and engine block plane are straight or warped. Inspection method: Put a ruler longer than the cylinder head on the plane of the machine body and cylinder head respectively, and measure whether it meets the requirements with a thickness gauge. Otherwise, it should be polished and leveled.
3. The selected cylinder gasket must have the same specifications as the original cylinder, and the surface should be smooth, and there should be no damage, wrinkling or hardening due to aging, nor too thick or too thin. When installing, the curled side faces the cylinder head. For some high-strength, high-power supercharged imported diesel engines, the marked (such as TOP or up) side of the pure metal cylinder gasket used in installation faces the cylinder head (it cannot be replaced by ordinary cylinder gasket), and the elastic ribs at the cylinder port, oil port and water hole must be intact.
Causes of automobile cylinder explosion
What is cylinder explosion?
In a gasoline engine, when the mixture (air and fuel are fully mixed) enters the combustion chamber on the intake stroke, the piston compresses it on the compression stroke. After the spark plug ignites the high-pressure mixture, the pressure generated by its combustion is converted into the power of the engine. Although engine combustion can be simply described in a few words, I don't know how many doctoral and master's theses have been gained from the combustion research of internal combustion engines, and even many scholars and engineers have been studying the knowledge of combustion all their lives, so it still needs a lot of work to really understand the engine.
Precise design and control are needed because the combustion of the engine is very complicated. A slight control error or disorder will cause abnormal combustion, and "knocking" is abnormal combustion. Simply put, knocking is the abnormal pressure in the combustion chamber caused by abnormal combustion.
Automobile cylinder explosion: refers to the scrapping of the engine due to the piston expansion stuck in the cylinder due to high temperature. In severe cases, because the pressure is too high, the piston cannot move, and a thick flame will be ejected.
The reason is that the heat dissipation effect of the engine is not good, which makes the working temperature of the engine exceed the temperature that the original design can bear, and then the lubrication is insufficient due to poor oil quality or circulation, and the intake and exhaust system and ignition timing of the engine are not adjusted accurately. Finally, it should be the so-called cylinder explosion or cylinder contraction caused by excessive engine workload.
What if the car has a flat tire?
Under normal circumstances, automobile cylinder explosion will seriously damage the engine, so it can only be recovered through overhaul.