Most major vehicle manufacturers recommend that drivers should change their brake fluid at least every two years. This is because brake fluid is a hygroscopic fluid - meaning that it absorbs water over time reducing its effectiveness.

If the fluid is not changed before the water content reaches the 3% mark, the water brings down the normal boiling point of the brake fluid and air bubbles are created as a result. Once this happens, the brakes become ineffective and dangerous.

If that wasn't bad enough, a motorist probably won't even be aware that this has taken place because the braking system will appear completely normal until the brake fluid reaches the reduced boiling point - which usually occurs after braking heavily.

What happens next is this: the brakes take on a sponge-like feeling and don't work - so the car fails to stop. If the driver happens to be on a hill or driving along a motorway when this happens, the consequences don't even bear thinking about.

The only way to ensure that this doesn’t end up happening to you is to check that your brake fluid is changed at least every two years –
preferably once a year. A mechanic can do this as part of your regular service, just mention that you want it done and they should be happy to oblige

If your brake master cylinder becomes empty, the pedal will go right down onto the floor and you will end up needing to bleed your brakes as well as adding more brake fluid. If you don't know how to do this, or anyone that does, don't take a risk - get a professional to do it for you. They will flush out and refill the braking system, making sure that it is up to scratch and roadworthy.