Brake Fluid Facts to Keep You Safe On The Road
Have you ever applied pressure on your brakes and found they had a “mushy” feel? Your brake fluid may need a change. Brake fluid is one of the most important components of your brakes. It keeps your brakes working properly and your car running safely. This hydraulic liquid or oil is also used in other vehicles like motorcycles, some trucks, bicycles and hydraulic clutches.
When you apply pressure on the brake, the fluid transfers the force to the braking mechanism near the wheels. This liquid is chemically composed from either glycol-ether based materials or, silicone based or mineral oil. It is designed to tolerate both and cold and high temperatures without becoming thick or boiling because it must maintain its viscosity even in extreme cold, if your brakes are to function reliably.
There are certain standards set down for the manufacturer of brake fluids in North America. Most fall under the US’s Department of Transportation’s (DOT) ratings, with the three main types being denoted as DOT3, DOT4 and DOT5.
DOT3 and DOT4 are glycol-based fluids that absorb moisture while DOT5 is a silicone-based fluid that does not. Silicone-based materials are colored purple to distinguish them from the glycol-based ones and provide more consistent performance, even in extreme weather. However, glycol-based liquids are less compressible and allow for quicker braking than silicone-based ones.
Local governments, such as those in Alaska and the Azores, may use different standards for normal temperature and humidity ranges. Organizations such as the SAE are the ones who define the best practices or specifications accepted globally.
Changing Brake Fluid
You should change or flush your brake fluid every 1 or 2 years or once moisture seeps in and the water content increases too much. Remember not to mix fluids with differing DOT ratings. You can use commercial testers and strips to measure water content in brake fluid.
Depending on your car model, the vehicle manufacturer may require more frequent changes to ensure the brakes work safely and reliably. Other things which degrade are the corrosion inhibitors. You cannot “top up” brake fluid. Low levels are usually indicative of a problem, such as wear and tear or a leak.
Because glycol-based fluids are toxic and flammable and capable of stripping paint, its best not to use a DIY approach to change them, but to take your vehicle to a mechanic to get it flushed and replaced. Brake fluid can be stored for a maximum of two years, as long as the seal is intact and it has been stored in good conditions.
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