Head gasket
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It can also take out the whole bottom end of your engine: broken or bent pistons and rods, cracked block, etc. | It can also take out the whole bottom end of your engine: broken or bent pistons and rods, cracked block, etc. | ||
| − | == | + | ==Head gasket sealants== |
| + | Most modern head gaskets are installed dry, without any sealant. Follow the manufacturer's instructions. | ||
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| + | ==Removing a head gasket== | ||
| + | Use a putty knife or gasket scraper. You can also use acetone thinner, ''(confirm)'' or [http://www.permatex.com/products/automotive/automotive_gasketing/gasket_removers/auto_Permatex_Gasket_Remover.htm Permatex gasket remover]. Don't use wire brushes -- the wires can break off, get into the oil pump, and lock it up. (What about 3M "hair brush" pads? What are those? Safe to use?). | ||
==Head gasket re-torquing== | ==Head gasket re-torquing== | ||
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Re-torqueing should be done when the engine is completely cool. | Re-torqueing should be done when the engine is completely cool. | ||
| − | + | ==Reasons why head gaskets fail== | |
*Overheating, possibly from a blown hose, water pump, or thermostat. | *Overheating, possibly from a blown hose, water pump, or thermostat. | ||
*Engine pre-ignition or detonation. | *Engine pre-ignition or detonation. | ||
*Improperly torqued cylinder head. | *Improperly torqued cylinder head. | ||
*Faulty cylinder head bolts. | *Faulty cylinder head bolts. | ||
| − | *Some blocks are more prone to head gasket failure, because the bolt positioning applies uneven pressure | + | *Some blocks are more prone to head gasket failure, because the bolt positioning applies uneven pressure. |
| + | *Stretched cylinder head bolts. | ||
| − | ==Compression testing== | + | ==Compression and leakdown 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. | *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. | ||
| + | *If you can, do a leakdown test. | ||
==When replacing a blown head gasket== | ==When replacing a blown head gasket== | ||
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*Oil the tips of the cylinder head bolts with light oil. ''(confirm this, and expand)'' | *Oil the tips of the cylinder head bolts with light oil. ''(confirm this, and expand)'' | ||
*Sometimes a sealant will need to be used on the head bolts, as they may intersect the water jackets, and be exposed to engine coolant. | *Sometimes a sealant will need to be used on the head bolts, as they may intersect the water jackets, and be exposed to engine coolant. | ||
| + | *Change the oil and oil filter too -- they're likely contaminated with coolant. | ||
| + | ==Re-using head gaskets== | ||
| + | Some head gaskets are re-usable, and some aren't. Copper head gaskets are re-usable, although they have to be re-annealed. Even if a head gasket is re-usable, many people prefer to use a new one. The labor involved in replacing a head gasket, and the potential for engine damage from a blown gasket, are too great to risk. | ||
==Copper head gaskets== | ==Copper head gaskets== | ||
| − | Copper head gaskets are typically less forgiving. They're commonly used in high-performance applications. They are re-usable, although they have to be re-annealed. | + | Copper head gaskets are typically less forgiving. They're commonly used in high-performance applications. They are re-usable, although they have to be re-annealed. They seal combustion well, but they are prone to leak coolant. They're less forgiving to imperfections in the head and deck surfaces. |
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| + | To take full advantage of copper head gaskets, you have wire o-rings machined into the block or the head. You'll also need a good sealer around the water passages. | ||
However, copper head gaskets have superior thermal conductivity, thought to stabilize head and block temperature, and provide elasticity and strength. | However, copper head gaskets have superior thermal conductivity, thought to stabilize head and block temperature, and provide elasticity and strength. | ||
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==Suppliers of head gaskets== | ==Suppliers of head gaskets== | ||
*Fel-Pro | *Fel-Pro | ||
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