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CDifficulty 3/5

In a conventional liquid-cooling system with a correctly working thermostat, what restricts coolant flow to the main radiator while the engine is cold?

Correct answer

Automatic closure of the thermostat towards the main radiator.

The thermostat remains closed towards the main radiator until the specified temperature is reached. This helps the engine warm up; coolant can still circulate through the internal or bypass circuit. Regulation is automatic, not an instruction for the driver to close a valve or disconnect the pump. A thermostat stuck open is one possible reason an engine fails to reach normal temperature and should be checked before repair.

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  • Automatic closure of the thermostat towards the main radiator.

  • The driver manually disconnecting the pump.

  • Keeping the thermostat permanently open at every temperature.

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