why most cars make a clicking sound right after it turns off
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When the car engine is running, it gets very hot. Most materials, like the metal of the engine, expand slightly when heated. When the engine turns off, it starts cooling down, which makes the metal shrink. The clicking sound is from this contraction causing parts of the metal to slip or snap past other parts.
The same sounds would happen when it was warming up, but the sound of the running engine generally overwhelms it.
The hottest parts of the engine – the exhaust pipes and the catalytic converter – have heat shields around them to protect other materials. They are thin metal, and when they cool down they change shape and that makes a “ticking” noise.
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