How does increasing system pressure affect the coolant boil point?

How does increasing system pressure affect the coolant boil point?

• A. It raises the boiling point.
• B. It lowers the boiling point.
• C. It has no effect.
• D. It causes coolant to evaporate faster.

Answer: (A)

Raising system pressure raises the coolant’s boiling point. In a closed, pressurized cooling system, boiling occurs when the liquid’s vapor pressure matches the surrounding pressure. The radiator cap and system design increase the ambient pressure on the coolant, so it must reach a higher temperature to start boiling. That’s why automotive cooling systems can operate at temperatures above 212°F (100°C) without boiling, thanks to the added pressure from the cap and the sealed circuit (and coolant mix can push this even higher). So increasing pressure makes boiling harder, not easier.

Raising system pressure raises the coolant’s boiling point. In a closed, pressurized cooling system, boiling occurs when the liquid’s vapor pressure matches the surrounding pressure. The radiator cap and system design increase the ambient pressure on the coolant, so it must reach a higher temperature to start boiling. That’s why automotive cooling systems can operate at temperatures above 212°F (100°C) without boiling, thanks to the added pressure from the cap and the sealed circuit (and coolant mix can push this even higher). So increasing pressure makes boiling harder, not easier.