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C1Difficulty 3/5

In a cooling circuit designed to operate under pressure, what effect does increased pressure have on the boiling temperature of the same coolant?

Correct answer

Raise the temperature at which the coolant boils.

It raises the coolant’s boiling temperature compared with the same liquid at lower pressure. This helps prevent boiling within design conditions; it does not guarantee that boiling is impossible or impose a universal optimum temperature of 120°C or below 80°C. The value depends on pressure and coolant composition. Follow the manufacturer’s coolant, cap and maintenance specifications. Never open a hot, pressurised circuit: pressure release can cause boiling and liquid or steam discharge with a burn risk.

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  • Always set every engine’s optimum temperature to 120°C.

  • Raise the temperature at which the coolant boils.

  • Make coolant boiling impossible under every condition.

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