A head gasket is a gasket located between the engine block and the cylinder head (s) in the internal combustion engine.
The aim is to seal the cylinder to ensure maximum compression and avoid leaking coolant or engine oil into the cylinder; thus, this is the most important sealing application in any machine, and, as part of the combustion chamber, it shares the same power requirements with other combustion chamber components.
Video Head gasket
Type
- Multi-Layer Steel (MLS) - Most modern head engines are manufactured with MLS gaskets. It consists of two to five (usually three) thin layers of steel, inserted with elastomers. The contact face is usually coated with a rubber-like layer like Viton attached to the cylinder block and cylinder head while the inner layer is optimized for durability.
- Solid copper - a solid copper sheet, and usually requires a special machining called 'o-ringing' that places a wire around the periphery of the cylinder to bite the copper. When this is done, copper gaskets are very durable. Recently the company has begun to produce copper gaskets with integral insulation cables that allow their retrofit into machines without engine block removal for machine work.
- Composites - older technology. Usually these are made of asbestos or graphite but are more susceptible to explosions than new gaskets. Asbestos gaskets are becoming increasingly scarce due to health problems.
- Elastomeric - the type of gasket used by Rover on their K Series machines. These are used core steel plates with formed in place of silicone rubber beads to seal oil and cooler channels. Bores are sealed by rolled steel fire rings in a more conventional way. The idea behind the gasket design was to produce a production version of the technology used in the F1 engine at the time. The original app packing on a smaller version of the K Series was very successful. However, redesigning the engine produces persistent problems with the design - the shared interface becomes unstable and the gasket can not handle it.
The cost of replacement gaskets is usually not extreme, but the total repair price is very high. This is because the process of removing/replacing the head of the machine is very time consuming - about 75% of the cost will be the workforce. In addition, unprocessed and broken gaskets usually seriously damage the engine, requiring more expensive work.
Maps Head gasket
Gasket problem
The usual internal combustion engine is a four-step gasoline water-cooled design. It uses three fluid circuits that work:
- Combustible air/fuels
- Water-based cooling, usually with mixed glycol
- Motor oil for lubrication
All this is important, but should not be allowed to mix. In addition to sealing the cylinder, the head gasket also seals water and oil channels between head and block. Any connectivity between the two will cause engine failure, or significant problems like oil burning (smoke from the exhaust). Blue exhaust fumes may signal oil burning. White exhaust fumes are an indicator of cooling combustion, another sign of head gasket wear.
Sometimes, compression in the cylinder will cause a leak to form in the gasket and the gasket should be replaced, or severe damage may occur ( "blowing head blow"). This problem has been compounded by the use of aluminum rather than the iron cylinder head; while lighter than iron, aluminum has a much larger thermal expansion rate, which in turn causes more pressure to be placed in the head gasket. Machine makers have responded to this by adding a nonstick coating such as Teflon to the head gasket surface.
If the gasket fails, various problems may occur, ranging from compression loss (leading to power reduction, or rough machine), to discharging forced gas into the cooling system, causing the engine to overheat and increasing engine wear due to the motor oil mixed with antifreeze. The coolant can leak into the cylinder, causing the exhaust to release the vapor and the catalytic converter becomes damaged. If a large amount of coolant does this, a hydrolock can occur, causing extensive engine damage. Sometimes, all that might happen when a blowing head gasket is an excessive steam burst from the exhaust; but the machine can act and move as usual, until all the cooling is gone and the engine gets too hot. In other instances, compression leaks into small spaces between the gasket, as well as the cylinder head or trap engine block which is then released when the engine is turned off. The air then passes into the cooler and creates an air bag. Sometimes these airbags can get trapped inside the engine coolant thermostat, leaving it closed and causing further heating, thus creating more gaps between the gasket and the machine. The airbag can also cause the engine to discharge the coolant into an overflow tank or expansion, thus reducing the amount of coolant available in the engine to keep it cool.
The condition of the head gasket is usually investigated by checking the compression pressure with a pressure gauge, or better, leakage test, and/or noting the indication of combustion gases in the cooling system on the water-cooled engine. Oil mixed with refrigerant and excessive coolant loss without obvious cause, or the presence of carbon monoxide or hydrocarbon gas in the cooling system expansion tank can also be a sign of head gasket problems. A good sign of head packing failure in water-cooled engines is the presence of mayonnaise-like substances in oil, often seen in dipsticks, or oil filler caps. However, the presence of this substance is not a conclusive proof of the failure of the head gasket, since the oil can mix with the cooler through another pathway.
A leak head gasket can be classified as external or internal. The external leakage can be identified as the accumulation of oil and refrigerant under the machine. The presence of a coolant can be detected by irradiating the black light on what appears to be an oil leak; the appearance of cooler will appear under black light. An external leak may also appear as described earlier in the oil. Internal leakage can usually be diagnosed by excessive cooling accumulated in the expansion tank along with the presence of hydrocarbons in the form of foam. The possibility of steam or condensation and/or water (from road or rain) builds (in the installation of aftermarket products) from the external breath or capture tank from the head (rocker cover) can also cause foaming or foam buildup in oil but very unlikely.
References
External links
- Ask's Head Gasket and Valve Covers Q & amp; A
- How to Fix Your Head Gasket - An example of how the headgear is replaced.
Source of the article : Wikipedia
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