Likely Causes of Brake Failure

Likely Causes of Brake Failure

Did you know that overheating contributes to brake failure? No, me neither.

How car brakes work

Knowing the importance of your car brakes, here is a brief explanation of how they work, and can fail if neglected.

The brake fluid reservoir in your car is normally located under the bonnet and usually against the back of the engine compartment or near the base of the windscreen. This fluid flows into tubes which connect the brake pedal with the pistons of the disc brake or the cylinders of the drum brake.

When you apply your foot to the brake pedal, brake fluid transfers this force into pressure to the front and rear brakes and stops the vehicle. This works because liquids are incompressible.

However, various influences can greatly affect the condition of this liquid over time including severe overheating.

Here’s why.

1/ Severe Overheating

Severe overheating can happen if the brakes are overused on a hill, for example, thus raising the boiling point of the fluid. This is called an evaporative reaction and in turn can lead to the formation of bubbles. When the pedal is pressed again, the air bubbles are compressed, but hardly any force – if any at all – is transmitted. This lack of a power transmission ultimately leads to your brakes failing.

If your brakes are grinding, squealing or simply not working well enough, it’s time for a garage check to see if your brake pads, discs and fluid levels are in order.

2/ The Presence Of Water in Brake Fluid

The presence of water in brake fluid is another reason for reduced braking performance. Over a period of time, brake fluid starts to absorb water through small gaps in the joints of pipes and hoses. The weak point is often the ventilation hole in the cover of the tank, which provides the necessary ‘atmospheric’ ventilation to deal with fluctuating brake fluid levels. However, this very atmospheric humidity can then enter the brake fluid via this ventilation hole.
In an ideal world, brake fluids should have a water content level of around 0.05 per cent, which increases year on year for the reasons stated. When the 3 per cent mark is exceeded, the boiling point of the fluid drops from between 205°C and 260°C (the dry boiling point) to between 140°C and 180°C (the wet boiling point).

When the water content exceeds 3.5 per cent, it’s vital the brake fluid is changed because the wet boiling point has been reached, and the brake fluid could now ‘boil’ when you are braking. This can cause untold danger and impaired braking performance.

Where your brakes are grinding, squealing or simply not working well enough we recommend members visit a FOXY Lady Approved garage and ask the professionals for advice.

Please note that your brakes should have been checked at your last car service so if it’s been a while since your car was serviced, there may be other critical safety-related areas in need of attention. Don’t risk this.

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