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I took a look under the hood of my friend’s car and saw this colorful coil:

Colorful coil

What is this?

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It's part of the exhaust. Most likely it's part of the exhaust gas recirculation (EGR) system. The part you are pointing out is a part which allows a bit of flex without any damage coming to the tube as a whole.

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  • Why does it have this color?
    – hb20007
    Aug 28, 2021 at 22:01
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    Because it's been heated and the type of metal it's made out of, I'd assume? I'd bet the metal is a bit softer than the regular exhaust pipes to allow it to flex better. This may have caused the color. It's definitely nothing to worry about. Aug 28, 2021 at 22:05
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    It is stainless steel . the color is heat tint caused by different thicknesses of oxides. Just like a motorcycle stainless exhaust. Least thickness ( lower temperature ) gold . then pink, then pinkish blue, then blue , then purple ( thickest = hot). Then it will turn black if the oxide is thick enough. Steel goes through the same color range at much lower temperatures. Aug 29, 2021 at 16:59

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