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Correct!

You're about to drive an unfamiliar vehicle. What should you do if you think there may be moisture in the air-brake reservoir?

Assume the system has automatic drain valves
Find out whether you need to drain the system manually
Correct answer
Nothing; it's the vehicle owner's responsibility
Leave the engine running for a while before driving

DVSA theory test explanation

Moisture in the braking system can cause serious problems, especially in cold weather, when it could freeze and stop the brakes from working. Most modern vehicles have a system that drains automatically, but make sure you know which system is fitted to any vehicle that you drive.

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