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Brake Fluid Replacement

When does brake fluid need changing?

Brake fluid is a vital component of your car’s braking system. The brake fluid often referred to as hydraulic fluid, is part of the hydraulic system that makes your brakes work. When you apply pressure to your brake pedal the fluid is pressurised, pushing the brake pads onto the discs to slow the car down. This action is impossible without brake fluid.

Brake fluid loses its effectiveness over time as it is hygroscopic which means it absorbs water. As the water content of the fluid increases air bubbles are created causing the brakes to lose their effectiveness and become dangerous. This is evident when brakes begin to feel spongy.

How often should brake fluid be changed?

Brake fluid can get contaminated as it absorbs water which reduces the boiling point of the fluid, therefore it is recommended that it is changed in line with your vehicle manufacturer's recommendations which is generally around every 24 months or 24,000 miles, whichever comes first.

What happens when brake fluid is low?

Your braking system can be affected if the brake fluid is low causing a vibration to be felt when braking. Where brake fluid is very low this can allow air to enter the braking system which could result in a loss of brakes. A noise coming from the brakes when pressure is applied also signals an issue and the brakes need to be checked by a professional.

Can you just add brake fluid to your car?

If you suspect your brake fluid is low, you can top up the liquid yourself. First, you need to ensure you are parked on a flat surface, locate the brake fluid reservoir situated under the bonnet then wipe the reservoir cap to prevent debris from falling into the reservoir. Slowly add the brake fluid to the master cylinder reservoir taking care not to overfill it. The master cylinder will have a MAX level to prevent overfilling. You MUST ensure that you use the correct brake fluid for your vehicle (Refer to manufacturer handbook for further information)

Overfilling can mean that the brake fluid will not have enough room to expand and will leak out of the reservoir causing a mess. Problems can also occur with the braking system such as the brakes feeling like they are still engaged, often referred to as brake dragging.

Does changing brake fluid improve braking?

Changing the brake fluid will improve braking providing there are no underlying issues with your braking system. Ageing brake fluid will become contaminated with water and metal particles from the parts that make up the braking system, changing the fluid will prevent corrosion and the components eventually failing.

Does brake fluid go bad?

The recommendation that you change brake fluid every two years or so is due to the fact that it will go bad from absorbing moisture and metal particles over time and eventually its performance will be reduced.