The Function of The Engine Gasket

The core functions of gaskets are "sealing" and "adjusting". They are thin sheet components installed between two or more connected parts. Although they may seem insignificant, they are crucial for the normal operation of the engine.

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Core Function Decomposition

Sealing function (the main function)

This is the fundamental task of the gasket, which is to prevent various fluid leaks and pressure losses within the engine. Depending on the installation location, the main sealing points are:

· Sealing liquids:

· Engine oil: Such as the gasket between the oil pan and the valve cover, the gasket between the timing cover and the engine block, etc., to prevent oil leakage from the joint surfaces.

· Gasoline: Such as the gasket between the carburetor or the fuel pump and the engine body, to prevent fuel leakage (very dangerous).

· Coolant: On some water-cooled engines, such as the gasket between the water pump and the engine block, to prevent coolant leakage.

· Sealing gases:

· Cylinder gasket: This is the most important gasket in the engine. It is installed between the cylinder head and the cylinder block, responsible for sealing the combustion chamber, withstanding extremely high temperatures and pressures during explosions, and also separating the oil passage and the cooling water passage. Failure of the cylinder gasket can lead to power loss, water ingress in the oil, bubbling in the radiator ("pressing machine") and other serious problems.

· Intake manifold gasket: To ensure that air/mixture only enters the cylinder through the intake port, preventing air leakage that causes unstable engine operation and insufficient power.

· Exhaust manifold gasket: To ensure that all high-temperature exhaust gases are discharged into the exhaust pipe, preventing air leakage (causing "puffing" noises) and possibly affecting the operation of the oxygen sensor.

2. Adjusting clearance and compensating for tolerance

The thickness of the gasket can be adjusted to fine-tune the gap between the two connecting parts.

For example: When installing the magnetic motor flywheel or gears, sometimes a thin adjustment gasket is used to ensure that the axial clearance (tolerance) is within the standard range, preventing scratches or abnormal noises when the parts rotate.

3. Buffering and Loosening Prevention

Some gaskets (such as some cork or composite material gaskets) have a certain elasticity, which can absorb the minor displacements caused by thermal expansion and contraction or vibration between the components, preventing the connection bolts from loosening.

4. Electrical insulation

In a few specific locations, the gaskets may also need to serve an insulating function, such as preventing certain sensor housings from short-circuiting with the engine block.

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Common gasket materials

Depending on the working environment (temperature, pressure, medium) of the application, the gaskets are made of different materials:

· Metal gaskets: such as steel, copper, and aluminum. Used in high-temperature and high-pressure areas, such as cylinder gaskets (nowadays, they are mostly multi-layer metal composite structures).

· Non-metallic flexible gaskets: such as rubber (nitrile rubber, fluorine rubber), cork, paper-based materials, asbestos (now rarely used). Used for sealing engine oil, water or low-pressure gases, such as valve cover gaskets, oil pan gaskets.

· Composite gaskets: composed of metal and non-metal materials, combining the advantages of both.

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Performance related to the fault

If the gasket fails (due to aging, damage or improper installation), it will cause a series of problems:

1. Leakage: This is the most obvious manifestation.

· Oil leakage: There are oil stains on the exterior of the engine, possibly from the valve cover, oil pan, etc.

· Water leakage: The coolant level decreases and there are water stains (with color) on the ground.

· Air leakage:

· Intake air leakage: The engine will exhibit unstable idle, insufficient acceleration, and too lean mixture.

· Exhaust air leakage: There is a "popping" sound at the exhaust pipe interface, and the power may decrease.

2. Severe engine failure:

· Cylinder gasket damage: The engine will exhibit symptoms such as high water temperature, significant power loss, emulsified engine oil turning milky white, and white smoke coming from the exhaust pipe (burning coolant), and immediate repair is necessary.

3. Strange noise: Some adjustment gaskets are worn or missing, which may cause improper clearance of mechanical components, resulting in friction or impact sounds.

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Maintenance Precautions

1.不可重复使用： For the majority of gaskets, after disassembly, due to compression deformation, new ones must be replaced. Otherwise， leakage is highly likely to occur.

2. Clean the surface: Before installing the new gasket, it is necessary to thoroughly clean the old gasket material， oil stains， and carbon deposits on both mating surfaces and keep them flat.

3. Correct torque and sequence： During installation， it is necessary to operate according to the specified tightening torque and sequence in the maintenance manual (for example， cylinder head bolts need to be tightened in a cross pattern from the center to the periphery in several stages). This is the key to ensuring uniform sealing and preventing deformation.

4. Use sealant when necessary： For some non-planar or highly demanding sealing areas， when installing the gasket， it may be necessary to use an appropriate amount of special sealant (such as silicone sealant)， but it should be noted that not all areas require sealing， and the amount should not be excessive.