Worth knowing

Brake Fade on the Kuranda and Gillies Ranges

A pedal that goes long halfway down and feels perfectly normal at the bottom is not imagination. It is heat, and there are two different versions of it.

Ordinary braking is short and occasional. You slow down, the pads and rotors absorb energy as heat, and then there is time for that heat to dissipate before the next stop.

A range descent is not that. It is several minutes of near-continuous braking, converting the vehicle’s potential energy into heat with very little chance to shed it. Everything gets hot: the rotors, the pads, the caliper, and eventually the fluid inside the caliper.

Braking systems are designed to handle this. What they are not designed to handle is doing it with fluid that has water in it.

Two different failures that feel similar

Pad fade happens when the friction material gets hot enough to stop working properly. The pedal still feels firm, but the car does not slow the way it should. You are pushing the same amount and getting less.

Fluid boiling feels different and is worse. Brake fluid is hydraulic: the system works because liquids do not compress. Boil the fluid and you get vapour in the lines, which does compress. The pedal goes long, or goes to the floor, and you get very little braking for the travel.

The distinguishing feature is what happens afterwards. Once everything cools, the pedal comes back and feels completely normal. Nothing is visibly wrong, nothing leaks, and the car passes any test you could do in a car park. This is why so many people talk themselves out of mentioning it.

Why the fluid has water in it

Brake fluid is hygroscopic. It absorbs moisture out of the air through the reservoir and, slowly, through the flexible hoses. It does this faster in humid air, and it does it whether the car is driven or sitting.

Water lowers the boiling point substantially. Fresh fluid has a very high boiling point; fluid a few years into its life can be low enough that a sustained descent will reach it.

The important part is that this is testable. Moisture content is measured, not estimated from the age of the car, and the brake repairs page covers what that involves.

What to do on the descent itself

Two things, and both are free.

Use a lower gear. Let the engine do a share of the work. In an automatic that means selecting a lower range rather than leaving it in drive. This is the single most effective thing available to you and it costs nothing.

Do not ride the brakes. Light continuous pressure the whole way down keeps the brakes hot continuously. Firmer, shorter applications with gaps between them let them recover. It feels less cautious and it is considerably safer.

If you tow, all of the above matters more, because you are managing more weight and generating more heat with the same brakes.

If it has already happened to you

Get the fluid tested, and mention what happened and where. A brake system that boiled its fluid on a descent is telling you something specific about the condition of that fluid, and it is a cheap thing to put right compared with what it is warning you about.

Also worth reading

What a Queensland Safety Certificate Actually Checks

The inspection has a defined scope. Knowing where it stops is as useful as knowing what it covers, particularly if you are the one buying.
How Often to Service a Car in Far North Queensland

The severe service schedule in the back of your handbook is not an upsell. Up here it is usually the one that applies, and it changes three things, not everything.
Why Car Air Conditioning Fails in the Build-Up

Air conditioning fails when it is asked to work hardest, which is why it always seems to go in October. The pattern of failure tells you the cause.

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We cover: Cairns, the southern corridor to Gordonvale, and north to Trinity Beach
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