Without brake fluid, a car’s brake system won’t work. It’s as simple as that. Brake fluid is a hydraulic liquid that fills the brake lines of a car. It’s non-compressible and hygroscopic (meaning that it absorbs moisture from the air), and it comes in several different types.
When a driver presses their foot down on the brake pedal, the brake fluid filling a car’s brake lines is what transfers the pressure from that pedal to the brake rotors in order to slow and stop the car. Without brake fluid, there is no medium to transfer the pressure, and therefore, no slowing and stopping. This is because air, in contrast to brake fluid, is compressible, so rather than transferring pressure, air will simply be compressed in the brake lines when a driver presses down on the pedal.
Brake fluid is clearly very important, then, and any problem with a car’s brake fluid could have serious consequences. With that mind, here are five dos and don’ts to remember when it comes to changing brake fluid.
Do Be Cautious When Working With Brake Fluid
Brake fluid is toxic, so you should always wear gloves and protective eyewear when performing a fluid change. It can also do significant damage to a car’s paint, so any contact should be avoided.
Do Change Brake Fluid Regularly
A good rule of thumb is that brake fluid should be changed every other year. There are exceptions to this, though. If a brake pedal starts to feel “spongy,” that’s a good sign that it’s time to change fluid, regardless of how long it’s been since it was last changed.
Brake fluid should also be examined if the brake lines are ever opened up during servicing. The fluid should be yellowish and translucent. If it’s not, then it probably needs to be changed.
Don’t Use Brake Fluid That’s Been Exposed to Air
One of the reasons that fluid should be examined if brake lines have been opened is that brake fluid begins to “go bad” very quickly after being exposed to air. For this reason, you should never use brake fluid from a bottle that’s been opened already. Use fluid from a freshly opened bottle instead.
You should also avoid unnecessarily opening the brake fluid reservoir, as this will allow air and moisture into the system. Instead, monitor the levels by referring to the MAX and MIN lines on the reservoir.
Do Bleed the Brakes When You Become a Mechanic
Bleeding brakes is the process of pushing new brake fluid through the lines, forcing out old fluid, as well as any gas bubbles, rust, or debris. If you fail to properly bleed the brakes when changing fluid after you become a mechanic, you could risk leaving air bubbles or other contaminants in the line.
Don’t Substitute or Blend Different Brake Fluid Types
As students in mechanic colleges know, brake fluid comes in several types and it’s important to always use the type of fluid recommended in a car’s owner’s manual, and not blend or substitute different types. The different types of fluid—DOT 3, DOT 4, DOT 5, and DOT 5.1—vary according to their boiling points and other factors, and one type of fluid is not generally substitutable for another.
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