Revision question · Braking systems

What could prevent air pressure from building up in an air-brake system in frosty weather?

Revision material from the imported DVSA bank includes source-checked Lanekind learning corrections. These corrections are not newly issued official examination questions, and practice does not reproduce a live test paper.

Answer options

Moisture in the air may form bubbles in the brake fluid

The air will contract, reducing the pressure

The dampness may cause valves to rust

Moisture drawn in with the air may freeze and cause a blockage

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Moisture drawn in with the air may freeze and cause a blockageThis was the right answer

Moisture in the air system can freeze and obstruct valves or pipes. Where fitted, the air dryer removes moisture between the compressor and reservoirs, not before compression. Maintain the dryer and drain arrangements to the manufacturer’s instructions; do not drive with unsafe brake pressure.

Reviewed reading for this question

Remove moisture after compression and before storageReviewed guidance summary · The archive’s reversed dryer position is corrected separately: the air is dried after compression, before entering the reservoirs.

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