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Why the Cylinder Head Must Always Be Machined When the Head Gasket Blows

Model: (Various brands) Various
Part: Cylinder head

Video tutorial

Let's see why, when the head gasket blows, the cylinder head must always be machined, and you cannot simply replace the gasket. The engine overheats, and the head (often made of aluminium) deforms, causing what is called "warping", which is a slight curvature or deformation.

Even if it appears straight to the naked eye, there may be a difference of a few hundredths of a millimetre. The new gasket requires perfectly flat surfaces to seal the oil passages, coolant, and combustion pressure correctly.

If the head is deformed, even slightly, the gasket cannot do its job. Machining involves placing the head on a milling machine that removes a very thin layer of material, just enough to make it perfectly flat. If we install a new gasket on a deformed head, the gasket will break after a short time, continuing the problems of coolant leakage and compression, risking a complete engine failure.


Posted on 18 October 2026 by ScegliAuto


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by ScegliAuto

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