During a long uphill climb in summer traffic, the temperature warning light comes on and steam begins to rise from the bonnet edges. What is the correct response?

Why B is correct

An overheating engine needs the load removed and the heat shed: air conditioning off, heater on full if you must limp briefly, and a safe stop off the traffic lanes with the engine shut down to cool on its own schedule. The cooling system at temperature is pressurised well above atmospheric, and a hot radiator cap opened by hand releases scalding coolant in a geyser aimed at whoever is holding it. Burns from cooling systems are a recurring emergency-room item precisely because the cap looks like a harmless piece of plumbing and is, at temperature, a pressure-vessel relief valve.

Why the other options are wrong

A. Open the bonnet immediately and loosen the radiator cap to release the pressure

The cap on a hot engine is the single most dangerous component in the scene. Loosening it drops the system pressure instantly and flashes the superheated coolant to boiling — out of the opening, upward, onto your hands and face.

C. Accelerate to increase airflow through the radiator and clear the temperature

Acceleration adds engine load, which is the thing generating the heat in the first place. More airflow helps only at constant load; flooring it up the same hill stacks load on load and turns a warning light into a head gasket.

D. Pour cold water over the radiator to bring the temperature down quickly

Quenching hot metal with cold water risks cracking components through thermal shock and does nothing about the root cause. Engines cool at the rate their mass and airflow allow; shortcuts with water cool impatience, not engines.

On the road

I-70 westbound in July, a loaded sedan climbs the grade and the temperature lamp lights. The driver goes airmail off, hazards on, onto the shoulder, engine off — and waits twenty minutes before anyone touches the bonnet. The cap comes off cold and the reservoir takes coolant without drama. The family in the car behind, who opened theirs steaming at the last overlook, spent the afternoon in urgent care instead.

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