Knowledge Paper on Causes, Inspection and Prevention of Cylinder Gasket Burning

• Reasons for Cylinder Gasket Burning

1. Burning Cylinder Gasket Caused by Uneven Tightening of Cylinder Head Nuts (Bolts)

A. In use, the cylinder head nuts (bolts) are not regularly inspected and tightened. Individual nuts (bolts) of the cylinder head are loosened, so that the cylinder head can not be evenly pressed on the cylinder body.

B. When tightening cylinder head nuts (bolts), first tighten the middle two rows of nuts, and then alternately tighten them from the middle to the left and right. Otherwise, the nut (bolts) will not be tightened unevenly, resulting in the cylinder gasket can not be evenly clamped between the cylinder block and the cylinder head.

C. Torsion wrench should be used when tightening cylinder head nut (bolt). For convenience, some repairmen use common wrenches to tighten, resulting in inconsistent torsion, some bolts with too large torsion, and some bolts with too small torsion, resulting in cylinder head can not be uniformly pressed on the cylinder block.

D. Torsional moment of cylinder head nut (bolt) is too large to exceed the prescribed value, which causes cracks in cylinder head. Cylinder head bolt and bolt hole slip, deformation, or bolt elongation, body bolt hole protrusion, so that the cylinder head and body seal is not strict.

As a result, the pressure on the joint surface of cylinder block and cylinder head is insufficient, the sealing of the joint surface is not good, and the gases of high temperature and high pressure rush out from the gap with small local torsion and burn the cylinder gasket.

2. Burning Cylinder Pad Caused by Uneven Joint Surface between Cylinder Head and Block

A. When repairing and replacing parts, no attention should be paid to checking, so that the combined plane of cylinder head or body is warped and deformed, or there are ablation, rust, pits and pits, which can not be repaired and grinded in time, so that the flatness of the bottom surface of cylinder head or the top surface of the body exceeds the prescribed value.

B. When replacing the insert of the pre-combustion chamber or swirl chamber, the insert does not meet the technical requirements. When the insert is too thick and protrudes out of the cylinder head plane, the pressure between the cylinder head, the cylinder pad and the cylinder liner cannot be uniformly pressed. When the insert is too thin and below the cylinder head plane, the gas will escape from the insert.

C. Incorrect height of cylinder liner shoulder protruding from body plane. If the protrusion is too high, the shoulder of the cylinder liner will hold the cylinder head up, so that the cylinder pad can not be pressed; if the plane value of the protrusion body is too small or no protrusion, even lower than the plane of the cylinder body, the cylinder head can not press the cylinder liner, and the cylinder pad can not be pressed and sealed well.

D. The height difference of the protruding cylinder surface on the shoulder of each cylinder liner of a multi-cylinder diesel engine is not uniform. The cylinder liner with excessive protrusion will hold the cylinder head up, resulting in the cylinder liner pressure not tightening.

Above conditions, lead to the loss of the function of the cylinder gasket, make the cylinder seal worse, high temperature gas will burst out from the gap, so that the cylinder gasket burned.

3. Cylinder gasket burning due to improper use and assembly

A. Cylinder gaskets are used for too long. After many disassemblies and assemblies, the cylinder gaskets lose elasticity. If they are not treated or replaced, they can not be used again, which can not play a good sealing role.

B. Carbon deposit, dirt, rust and convex hull on the combined plane of cylinder head, cylinder cushion and body are not removed carefully during installation, so that a gap is formed between the joint surfaces after installation.

C. When installed, there is one-sided flanging or crimping on the cylinder gasket, and one side of the flanging or crimping is mistakenly oriented towards the cylinder surface, which makes the gas easy to rush into the cylinder gasket from the flanging position.

D. When installing, add butter on the surface of the cylinder gasket, or immerse the cylinder gasket directly in diesel oil, then install the wrong way after removing it.

The above conditions and reasons are easy to cause cylinder gasket burning.

4. Burning Cylinder Pad Caused by Excessive Temperature of Diesel Engine

A. High compression ratio or too small compression clearance result in high pressure at the end of compression and high temperature during expansion combustion.

B. Too small or too large advance angle of fuel supply results in too high temperature of diesel engine, and the heat can not be transmitted in time, resulting in overheating of cylinder head and cylinder block.

C. Incorrect valve timing, blockage of intake or exhaust system, insufficient intake and unclean exhaust, poor lubrication of moving parts, failure of cooling system and poor heat dissipation effect all cause overheating of diesel engine when working.

D. Locomotives often run under overload or diesel engines run under overload for a long time, which results in high temperature of diesel engines.

Under the above conditions, the cylinder gasket is subjected to the long-term effect of high temperature, asbestos material deteriorates and hardens, and gradually loses its elasticity and is burned.

5. Burning loss caused by poor manufacturing quality of cylinder gasket products

A. The material used for manufacturing cylinder gaskets is too poor in quality, insufficient in elasticity and high temperature resistance to meet the sealing requirements of the joint surface between cylinder head and cylinder block.

B. Because of the poor processing technology, the cylinder gaskets produced are irregular, the flanging is not tight, and the asbestos paper laying in the metal wrapping is uneven.

C. The position distance and geometric shape of the cylinder gasket holes manufactured do not meet the technical requirements, such as the wrong position of the bolt holes in the cylinder gasket, the wrong position of the cylinder liner holes in the cylinder gasket, and the unequal position of the waterway holes in the cylinder gasket.

In this case, even if the cylinder gasket can be installed reluctantly, there will be undulations, pressure is not tight, pressure is not achieved, leading to the cylinder head and cylinder block fitting is not strict, high temperature gas impact will burn the cylinder gasket.

• Detection method of cylinder gasket burnout

The cylinder pressure gauge is used to measure the compression pressure of two adjacent cylinders of the engine. If the pressure is very low, the cylinder gasket is usually not well sealed. Then do the following specific tests:

1. Testing the Sealing of Cylinder Gasket with Rubber Hose

Start the engine, one end of a rubber hose is close to the ear, and the other end is searched along the connection between the cylinder head and the cylinder block which may be badly sealed. If the cylinder gasket is badly sealed, the exhaust sound can be clearly heard at the leakage site.

2. Testing the sealing of cylinder gasket by looking at radiator spray

Open the radiator cover, keep the engine idling, observe the cooling fluid filling port of the radiator, quickly step the acceleration pedal to the bottom, if there are bubbles continuously coming out of the cooling fluid when suddenly accelerating, it shows that the cylinder gasket is not well sealed. The more bubbles, the more serious the leakage. In serious idle condition, the radiator outlet will turn over.

3. Detection of cylinder gasket sealing by exhaust gas analyzer

Some engine radiator coolant filling holes are under the iron plate, so it is impossible to see the bubbles. The radiator cover can be opened, and the probe of the exhaust gas analyzer can be placed at the open radiator cover. Do not touch the coolant. If HC can be detected during rapid acceleration, the seal of the cylinder gasket is not good.

4. Cylinder gasket leakage will cause engine temperature to be too high

If the power decreases, it should be replaced in time. Otherwise, it is easy to damage the cylinder head, cause the cylinder head to be scrapped, and cause the coolant to enter the combustion chamber.

• Prevention of Cylinder Gasket Burning

1. When disassembling cylinder head, it should be carried out under the condition of cooler. It is strictly forbidden to disassemble heat engine to prevent warping and deformation of cylinder head. When disassembly, it should be gradually loosened from both sides to the middle symmetrically for several times. If it is difficult to remove the cylinder head firmly, it is forbidden to use metal to knock on the cylinder head or to use sharp hardwares to wedge into the seam opening to prevent scratching the joint surface between the cylinder head and the cylinder head or damaging the cylinder gasket.

2. When installing the cylinder gasket, first check whether the cylinder head and the plane of the cylinder block are flat or warped. Inspection method: Use a ruler longer than the cylinder head and place it on the plane of the body and cylinder head respectively. Measure with gauge to see if it meets the requirements. Otherwise, it should be polished and smoothed.

3. The selected cylinder gasket must have the same specifications as the original cylinder. The surface should be flat. It should not be damaged, wrinkled or hardened by aging. It should not be too thick or thin. When installing, one side of the winding hole should be oriented towards the cylinder head. For some imported high-strength, high-power turbocharged diesel engines, the pure metal cylinder gaskets used should be installed with a mark (such as TOP or UP) facing the cylinder head (not to be replaced by ordinary cylinder gaskets), and the elastic ribs at the cylinder mouth, oil passage mouth and water hole must be intact.