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The Basics of Brake Fluid

What is brake fluid?

Brake fluid is a type of hydraulic fluid. Most likely, the fluid your car uses comes from a glycol-ether base. Glycol-ether solvents combine with other elements to change a liquid's boiling point.

Some brake fluid uses a mineral oil base. This base comes from the process of distilling petroleum and other fuel types. This transparent, odourless liquid reduces brake fluid's conductivity.

Why do you need brake fluid?

You likely know the term 'hydraulic'. Put simply, hydraulic machines use fluids for power and movement. Your brakes represent a small hydraulic machine.

Brake fluid transfers the force of your foot on the brake pedal to the brakes themselves. This allows your brakes to respond to partial pressure. Brake fluid lubricates the moving parts in your brakes to prevent overheating and corrosion.

Brake fluid must have a high boiling point so it remains liquid even when heated to high temperatures. Hard or prolonged braking generates heat, so it's essential that brake fluid withstands as extreme of temperatures as possible. Once fluid becomes vapour, it no longer provides adequate lubrication.

Most brake fluid doesn't boil until it reaches temperatures of 155C. However, over time moisture contamination can reduce brake fluid's boiling point, so fluid must be frequently checked and regularly replaced.

What are some signs of inadequate brake fluid?

When your brake fluid needs to be topped off or replaced, you may notice any of the following signs:

  • Brake Warning Lights: Your warning lights come on when your fluid runs low. This could happen over time throughregular use or suddenly as the result of a leak.
  • Pedal Problems: Most brake problems show in the way your pedal reacts. If your pedal feels spongy when you press it, it can indicate inadequate fluid.

How often should you have brake fluid checked?

Take your car or truck to a brake specialist immediately if you notice any of the signs listed in the previous section. These signs indicate a serious issue that could come before dangerous brake failures. For more information about brake maintenance and replacement, read our blog post "Brakes: When It's Time to Replace (http://www.stopmasterbrakes.com.au/brakes-when-itstime-to-replace)."

Even if you don't notice any danger signs, you should check your brake fluid every time you lift your hood to check on your other engine fluids. Newer cars even have transparent brake fluid reservoirs so you can see the fluid levels without having to do anything else.

Most brake fluid reservoirs have two fill lines: a maximum and a minimum. If you notice your fluid getting close to the minimum line, top it off. A reputable mechanic or brake specialist can help you determine the type of fluid to use. You can also find this information in your owner's manual. Most cars use Department of Transportation (DOT) 3 or 4 fluid.

You shouldn't risk mixing different fluid grades. If you don't feel sure what fluid you have, talk to a specialist before topping off the liquid.

How often should you have brake fluid changed?

In most cases, brake fluid needs to be replaced at least every two years. To know how often your vehicle needs its fluid replaced, check your owner's manual or talk to a mechanic.

New brake fluid appears amber and fairly clear. Over time, brake fluid darkens. If your fluid looks black when you check the levels, take your car in to have the fluid replaced.

If you have specific questions about your vehicle and its brake fluid, contact a trusted mechanic or a brake specialist.

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