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All you never knew you needed to know about your cylinder head and head gasket…

cylinder head

The cylinder head. What is it? What does it do? And why can it be so expensive to repair?

…..If you’ve ever needed the head gasket on your car replaced, you’ll know it can turn into an expensive job. But do you know why? I didn’t! Luckily our guys in the workshop do, and last week that’s what we’ve been doing.

head gasket arrow.png This is the cylinder head. Those four round bits are where the cylinders sit and the head gasket sits on top. The main job of the head gasket is to keep the cylinders sealed between the engine block and the cylinder head so they can compress properly and also to keep the coolant and oil apart. If there is a leak and they mix, it isn’t good for your engine.

This is pretty well buried in the engine so although the gasket itself isn’t too pricey, a big amount of the cost is labour is getting to the head gasket itself. Plus, there are lots of other things we check while the engine is split which takes time.

A good seal requires both faces to be completely smooth. To give us the best possible seal we had the cylinder head sent away, to be pressure tested and skimmed by a machining specialist. First, they pressure test the head to check for any cracks in the head itself, if they find it’s cracked, that can mean goodbye to that cylinder head :-o. Second, the head is skimmed. This involves removing or “skimming” a minute amount of metal off the surface of head making it perfectly smooth.

Once smooth, it means the head gasket gets a perfect seal and a new one, like this, can be fitted.head gasket

Finally (!), once all this is done we rebuild. Which can include needing new parts like bolts or injector seals but this depends on the car.

If your car is kicking blue or white smoke out of the exhaust it usually means there is some oil or coolant burning on the engine somewhere- possibly from a leaking head gasket.

So there it is! All you never knew you needed to know about the cylinder head and head gasket.

Think your car is having head gasket woes? Get in touch!


3 thoughts on “All you never knew you needed to know about your cylinder head and head gasket…”

  1. I believe that I need reconditioning on my cylinder head. Before reading this article I did not know exactly what a cylinder head was. Now I know the four round bits are where the cylinders sit and the head gasket sits on top. I also thought it was helpful for the explanation of what makes a good seal. I have never been good at fixing things by myself, so I will look more into getting help. But it is useful to learn about as many things I can about cars. Maybe one day I will be able to do minor repairs on my car.


  2. Thanks for this detailed description about Head gaskets. Gaskets are mainly used for Industrial and Automotive purposes. Fixing head gaskets is very challenging for me.


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