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How does a car's thermostat work?

Model: (Various brands) Various
Part: Thermostat

Video tutorial

This video shows us how the physical principle of the thermostat works, which is an example of a heat transformer into mechanical motion. When cold, the wax (a wax based on engineered paraffins) inside the capsule is solid and contracted.

A spring keeps the piston retracted and the valve closed. This blocks the flow of liquid to the radiator, allowing the engine to heat up quickly.

When hot, when the liquid reaches the specific opening temperature of the thermostat, the wax melts and expands, violently pushing the piston inside the capsule. The piston, in turn, acts against the force of the spring and pushes out the disc, opening the valve.

If the liquid temperature drops below the threshold, the wax solidifies and contracts; the spring becomes stronger than the contracted wax and closes the valve, pushing the piston back.


Posted on 22 January 2026 by ScegliAuto


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