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Automotive gaskets come in many materials, shapes and sizes and find application in many places.

I'm curious to learn more about why manufacturers use certain materials for certain applications.

I can give some examples from my BMW S62 engine:

  • The valve cover gaskets are made of rubber. They are sandwiched between the aluminium cylinder head and aluminium valve covers, and are exposed to oil during the engine's operation. They also have curvature to them to conform with the shape of the valve cover

  • The aluminium timing case and valve cover are separated by a set of metal gaskets. This will also be exposed to oil during the engine's operation

  • Some of the VANOS oil line banjo bolts utilize copper crush washers

  • The timing chain tensioner is bolted in with an aluminium crush washer to separate it from the timing case. The torque spec here is 50 Nm

  • This is going to take a book to answer ... great question, IMHO though. I'll see what I can do with it in my free time. Hopefully it will get fully answered before then! – Pᴀᴜʟsᴛᴇʀ2 Feb 10 '15 at 1:54
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Things to consider when choosing gasket materials:

  • Type of fluid/gas that should be contained
  • Pressure
  • Temperature range
  • Roughness of the sealing surfaces. The gasket needs to fill impurities in the sealing surfaces to keep the seal from leaking
  • Mechanical friction (Both for efficiency and resistance)

Perhaps the last one concerns other kind of seals more, on axles for example.

All these combined gives that a gasket needs to be chosen as a compromise. On a rough surface, you might want a thicker, softer gasket, but that won't work on high pressure applications. It might need to resist oil or fuel or keep drinking water uncontaminated.

Valve head and oil pan gaskets are often thicker and softer. I've seen cork and rubber for example, and they won't need much torque to seal. You can compare this to the head gasket, which needs to hold the pressure from combustion and withstand a lot of heat. It often have steel reinforcements to accomplish this.

Head Gasket

The head gasket needs a lot of torque to not leak, even though the surfaces are generally very smooth. The sometimes ridiculously specific torque specification are there to get the exact and even pressure on the gasket. Too little and it will leak, to much and something will be damaged (and probably leak).

You mention copper washers. A softer metal can be used between two harder metals to form a gasket since it will deform and follow the shape of the surrounding surfaces. (It's usually recommended to change the washer after every disassemble). In your case it was used on a Banjo connection. Imagine using a fiber gasket there, it would tear up when adding tension to the screw.

Many different materials are used for gaskets. Copper, Aluminum, plastic, rubber, cork and fiber being very common, but there are a lot of other types as well.

Read more:

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    I like this answer a lot. Good balance between breadth and depth. – Zaid May 26 '15 at 20:32
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It depends on the manufacturer specs. Different material alloys will need special gaskets between them as the materials of both sides of thew gasket will expand at different rates.

Keep in mind the fluids that the gasket seals.

My advice, the manufacturer standard, gasket types and width where calculated during engine manufacturing.

You can go out and study it there are books on gasket manufacturers specs and so on but you have to know the alloys the gasket is sandwiched between.

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