Brake Warning Light and a Mountain Descent
You are driving a fully loaded van (3,500 kg permissible mass) down a mountain road with a long 6% descent of about 4 km. Near the top, the red brake system warning light comes on and stays on. The pedal still feels firm and the van stops normally in a test at low speed. The handbrake works. You are 300 m from a lay-by and 1 km from a village. The outside temperature is 28 °C. You notice a faint burning smell that was not there before. Your load includes heavy tools. The road has no hard shoulder, only a narrow gravel edge.
1. What does a steady red brake warning lamp with a firm pedal most likely indicate, and what should you do immediately?
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A steady red brake lamp is a stop-driving warning, not a reminder. With a firm pedal and normal low-speed stopping, the most likely causes are low brake fluid level, a fault in the hydraulic circuit or its sensor, or a partially applied parking brake. The faint burning smell and the heavy load raise the possibility of dragging brakes or overheated components.
Immediate action: do not start the 4 km descent. Reduce speed gently using engine braking, signal, and pull into the lay-by 300 m ahead. On the narrow gravel edge, stop only if you can leave the lane clear. Switch off, let components cool, and check the brake fluid level only if you can do so safely. Do not open a hot reservoir or add fluid to a system you cannot inspect. If the cause is not obvious and correctable, call for assistance; a 6% descent with a suspect brake system and a heavy load is not a risk worth taking.
2. Explain why descending in a high gear with repeated braking is dangerous, and what technique you would use if you had to continue.
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Repeated braking converts the van's potential energy into heat faster than the brakes can shed it. On a 6% grade, a 3,500 kg vehicle gains a large amount of energy per kilometre; with a full load the brakes heat quickly, fluid can boil, and the pedal can go long or to the floor - fade. A high gear makes it worse because engine braking is minimal and the service brakes do nearly all the work.
If continuing were unavoidable, select a low gear before the descent so the engine holds speed (for many vans, second or third, depending on gradient), use the brakes in firm, short applications rather than riding them, and keep speed low and steady. Never coast in neutral. Watch for a long pedal, smell, or smoke, and stop to cool if any appear. Because the warning lamp is already on, the correct answer remains: do not descend until the fault is found.
3. What checks would you make at the lay-by, and what would make you decide not to continue?
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Checks: confirm the parking brake is fully released; look for fluid under the van near the wheels and master cylinder; check the reservoir level against the marked minimum; feel for unevenly hot wheels or a dragging caliper (carefully - they may be very hot); look for smoke or a blue-black glaze on discs. Check that the load has not shifted and that nothing is chafing a brake line.
Decide not to continue if: fluid is below minimum or leaking, any wheel is far hotter than the others, the pedal sinks under steady pressure, the lamp stays on after a correct fluid top-up, or the cause cannot be identified. A working handbrake is not a substitute on a 4 km descent. Arrange recovery or a mobile repair.