22 January, 2019

Save yourself some money, ditch the unnecessary brake flush

If you’ve taken your vehicle in to the garage for work doing recently, it’s probably a good bet that you’ve been asked if you want a brake flush (sometimes known as a brake fluid change). It only costs about £30 and the mechanic did recommend it….but were they right to recommend it?


Now from the outset, there are times when brakes do need flushing and essentially a brake flush is the process of removing old brake fluid and replacing it with fresh fluid.


Most modern vehicles use DOT 4 brake fluid, which is a glycol based fluid, that ensures when you press the pedal, pressure is created in the brake lines which in turn applies the brakes. Unfortunately though DOT 4 brake fluid is hygroscopic, which means it soaks up moisture (water) from the environment, which is bad for brakes.


When you apply the brakes you generate a massive amount of heat and that heat is dissipated through the braking components but also through the brake fluid. If instead of brake fluid, we used water, the water would get too hot and start to boil, which creates its own problems, but the same happens when you get too much moisture / water from the environment in your DOT4 brake fluid.


The way to tell whether your brake fluid is still useable is to test it’s boiling point. If the boiling point of your brake fluid (DOT 4 only) is between 155 degrees Celsius and 230 degrees Celsius then your brake fluid is still serviceable, albeit the closer you get to the lower figure, the more likely you are to need a brake flush.


But surely your mechanic checks your brake fluids boiling point?


That’s not always the case. Vehicle manufactures recommend that you change your brake fluid every 2 years. This is because it takes on average two years for your vehicles brake fluid boiling point to drop to the lower level, but what’s average?


Are you average? Is your neighbour average? Some people have vehicles for 12 months after which they need to change their brake fluid, but others have vehicles for 10 years and have never needed to change the fluid.


So the next time your mechanic recommends you have a brake flush or a brake fluid change, ask them whether they have tested the brake fluids boiling point and ask them what the boiling temperature was and make your own decision.