You may have heard about the hydraulic system. It is a widely used system in both automobiles and various industrial sectors. The very same process allows your brakes to work correctly. That's right, your car's brakes include a hydraulic system unless it is an electric vehicle which uses regenerative braking.

Whenever you push your brake pedal, it exerts a force on the small pistons inside brake caliper to compress. It squeezes brake rotors using the brake pads’ friction to necessarily slow down the car. The brake pedal of your car doesn't automatically connect to all four brake rotors. The brake lines allow diverting your single force to exert on the brake pedal onto the car's four brake system. And for this transmission to work, these lines contain hydraulic fluids, which we know as the “Brake Fluids."

Scientific Explanation for Function of Brake Fluid

When you apply pressure on a fluid in a closed container, it is uniformly distributed towards all directions of the container without attenuation. We describe the pressure as the force working on a unit of area. So, if we apply pressure on a smaller area and receive it from a larger area, the force will increase as the multiple of the area that is,

Received Force = Applied Pressure x Surface Area

Brake fluid works as the hydraulic fluid to transmit the pressure you apply on your brake pedal. Now, you may ponder, why don't we just use the most common fluid of all water? The answer is a little bit scientific. The more compressible the fluid, the more energy is wasted. So, the car brake fluid must have very low compress-ability even lower than that of water. It is a non-compressible fluid which converts all the energy that you release onto your brake pedal into braking pressure that slows your car.

Another reason for using special brake fluid is the heat produced during brakes. Frictional brakes create a lot of heat. So, the brake fluid must maintain its in-compressible nature at high temperature. Regular fluids are unable to do that.

You might be wondering about what happens when the fluid quality is not good and overheats. When overheated, it creates air bubbles that are compressible. Hence, when you step on the brake pedal instead of clamping the rotors and slowing down the car, the brake fluid compresses the air, which leads to brake failures.

Hopefully it is now clear to you how does brake fluid work.

How to Check the Brake Fluid of Your Car

Now that you hopefully know what does brake fluid do and why it is so important. You may want to check the brake fluid of your vehicle. But for newbies, it may be a little confusing as they don't deal with the braking fluid that much. In that case, you need not worry as we got your back.

There are usually two things to keep in checking the brake oil of your vehicle which are –

A. Fluid Level

B. Fluid Condition

Here we have added some very simple steps that you can follow to check your car’s brake fluid –

A. Checking the Fluid Level

Step#1. Park the Vehicle

• Start the process by parking your car on a flat surface. Make sure your vehicle is stabilized so that it can't rollover. It's a primary safety precaution whenever you're dealing with car maintenance.
  

Step#2. Lift Up the Car's Hood

• After parking your car on a flat surface, lift the car’s hood. Make sure that the engine is cold before doing so. The engine is pretty hot, even after small drives. Without caution, it can result in some very nasty burns. Therefore,it's better to do this when the car is kept on a flat surface at cold engine state.
  

Step#3. Search for the Master Cylinder

• The next thing to do is to search for the master cylinder. In most of the cars, you can find the master cylinder at the back of the engine bay. It’s easy to locate as you’ll find a reservoir above the master cylinder. Clean the cylinder and reservoir, if you find dirts on it.
  

Step#4. Inspect Fluid Level in Reservoir

•  After you have successfully found the master cylinder, the next is to check the fluid level. Your reservoir is most likely transparent like most other cars and should have lines marked "Min" and "Max." This will help you understand if your whether or not your fluid is running low.

Step#5. Adjust Brake Fluid If Required

• If you find the fluid level to be inadequate, you can adjust it easily. It most cases, you may find it below the maximum capacity.

•  If the fluid level is low, pour some brake fluid carefully into the reservoir Wipe up any spills, as brake fluids are most likely toxic and corrosive.

• Never forget to use the recommended brake fluid that your owner's manual suggests. There are three variants available, which are: DOT 3, DOT 4 and DOT 5. Three options bear their own properties. You can use DOT 4 brake fluid in some cars that mention for DOT 3 fluid, but never the opposite way around. However, use DOT 5 brake fluid only in vehicles that call for that specification. You can find the DOT specification of your car indicated at the reservoir cap.

Step#6. Reattach the Cap

• After adding or removing fuel, reattach the reservoir cap with proper tools and close the hood, and that'll all you need to do to check or adjust the brake fluid level.
  

B. Checking the Fluid Condition

The brake fluid's condition can tell a lot about how your car's braking system is working. Hence, it's wise to check the brake fluid condition regularly. Here's how to do it –

Step#1. Check the Fluid Color

• Most brake fluids are usually brown in color. But if you find the fluid to look black or dark, that means the fluid has decayed, and you may need to replace it with new fluid. However, that's not the only way to be sure, so keep testing the other parameters as well.
  

Step#2. Use Chemical Test Strip into Brake Fluid

• As brake fluid in your car ages, its corrosion inhibitors decay that causes a breakdown of the fluid. You can use chemical test strips to check the availability of copper in the brake fluid.The higher the copper level, the worse the corrosion inhibitors are. You can find these chemical test strips online or at local stores. These are quite handy when checking fluid quality.

Step#3. Test Fluid Moisture with Optical Refractometer

• Brake fluids are hygroscopic, so they absorb moisture from their surroundings as time goes by. The moisture dilutes and, hence, weakens the fluid's effectiveness, which results in corrosion of braking system components. In one and half years, brake fluids usually have up to three percent water, which lowers the boiling point from 40 to 50 percent.
  

Step#4.  Analyze Fluid's Boiling Point with Electronic Tester

• The ideal dry boiling point for new DOT 3 specification brake fluid is 401 F or 205 C and wet boiling point of 284 F or 140 C. Again, the dry standard for DOT 4 fluid is to boil at 446 F or 230 C and 311 F or 155 C for wet. The boiling point is lower means, the fluid's effectiveness is low.

• If you can’t find these tools, you can consult a mechanic who has both an optical refractometer and an electronic tester to perform these tests.

Conclusion

It's a widespread misconception that fuel is the only fluid a vehicle needs. Such ignorance often leads to life-ending accidents. Brake fluid is never less important than the fuel you feed your car to operate. It makes sure you're in control of your vehicle and allows you to adjust or stop your vehicle speed as you wish. Therefore, it's never a wise decision to overlook the significance of your car's brake fluid and you must get the knowledge how brake fluid works.