Editing Head gasket

Head gaskets provide the critical seal between the engine block and the cylinder head. They seal all of the combustion chambers, and prevent coolant and engine oil from leaking into the cylinders.

==Different types of head gaskets==
Copper and brass were originally used as head gaskets, followed by asbestos gaskets in the 1950's, and composite metal and impregnated fiber or graphite composites in the 1980's. In the 1990's the Mult-Layer-Steel gasket (MLS) came into widespread use. Most new engines today are designed with MLS gaskets.

In MLS gaskets, multiple thin layers of cold-rolled steel are coated with a very thin layer of elastomeric material. The elastomer "micro-seals" the surface imperfections in the metal, and resists gases, oils, coolants, and high combustion temperatures.

==Aluminum cylinder heads==
Though aluminum is lighter than cast iron, it expands faster. This quicker cycle of expansion and contraction stresses head gaskets. To handle this, a non-stick coating is often applied to the gasket, like Teflon or molybdenum.

With iron heads, a product can be applied for the opposite effect. Silicone, Viton, or other fuoroelastomer sealants are applied to '''increase''' the pressure between the iron heads and the iron block.

==Symptoms of a blown head gasket==
Some of the symptoms below may also indicate a cracked cylinder head.

*Foaming or bubbling coolant. Indicates head gasket has failed between a cylinder and a passage in the water jacket.
*Rapid pressure buildup in cooling system, before engine is warm.
*White smoke in exhaust.
*"Milkshake" oil.
*Oil in coolant.
*Low cylinder pressure.
*Two adjacent cylinders with low but equal pressure. Indicates head gasket failure between the two cylinders.
*Car misfires or runs rough at low speeds, due to antifreeze in the combustion chamber. '''(confirm)'''

==Reasons why head gaskets fail==
*Overheating, possibly from a blown hose, water pump, or thermostat.
*Engine pre-ignition or detonation.
*Some blocks are more prone to head gasket failure, because the bolt positioning applies uneven pressure

==Compression testing==
*If a compression test shows two cylinders with equal but low compression, then that may indicate a blown head gasket, with a leak between those two cylinders.

==When replacing a blown head gasket==
*Check to make sure the heads and block are straight. If they're warped, you could easily end up with another blown head gasket. This can be done with a straight edge and a feeler gauge. This is also a good time to check for cracks.
*Prep the surface (more info on this).
*Chase the bolt and stud holes. Clean with compressed air.
*Pre-fit the head gasket.
*Don't use sealant unless the manufacturer explicitly specifies it.
*Follow specific torque settings and bolt-tightening sequence perfectly.

==Suppliers of head gaskets==
*Fel-Pro
*Mopar Performance Gaskets (check)
*[http://www.bestgasket.com/ Best Gasket] -- Head gaskets for 1930's - 1960's American automobiles.

==References==
*[http://en.wikipedia.org/wiki/Head_gasket Head gasket] -- Wikipedia
*[http://www.allpar.com/eek/headgasket.html Replacing Chrysler, Dodge, or Plymouth head gaskets] -- Allpar.com
*[http://www.partstrain.com/ShopByDepartment/Head_Gasket Head Gasket] -- Partstrain.com
*[http://www.dupontelastomers.com/Applications/Automotive/head.asp Head Gaskets] -- DuPontElastomers.com
*[http://www.mobiloil.com/USA-English/MotorOil/Car_Care/DIY/Head_Gasket_Basics.aspx Head Gasket Basics] -- MobilOil.com
*[http://www.econofix.com/head.html Cylinder Head and Head Gasket Repairs] -- Econofix.com