head gasket

[julianne095]

what is a head gasket

[ronianna]

It's the actual 'seal' (usually made from cork or compressed fibreboard - sure there's a technical name for the material) between the top and bottom half of the main cyclinder engine block. Usually when it fails you notice either water in the oil (sometimes you can see whitish / cream / brown foam on the underside of the oil filler cap), steam from the exhaust or complete engine failure. It tends to leak a little first so your radiator water level may reduce slightly, but it always gets worse and eventually will become terminal. Sometimes it can just be replaced but often you need to have the head 'skimmed' which means having the two sides of the block that meet at the seal ground down so that they are flat and smooth. The cost of the seal itself is only a few pounds it's the labour involved in stripping down the block and rebuilding that costs. If you need the head skimming then that adds even more. Hope this helps - I'm no mechanic but I've had this happen on two of my cars so I've been there and had my wallet emptied to prove it. Good luck.

[Tim Baxter]

The head gasket is the pressure seal between the engine block and the cylinder head.

If it 'blows' you can loose engine pressure and gasses to the atmosphere, engine pressure and gasses to the cooling system, engine pressure and gasses to the lubrication system, all dependent on where the gasket fails.

In the 'good old days' of cast iron blocks and heads you could usually get away with just replacing the gasket but nowadays with alloy/iron blocks/heads combinations, their susceptibility to overheating is critical such that one will warp more than the other making it impossible to seal again without a 'skim'