How Much Brake Fluid Do I Need

How Much Brake Fluid Do I Need: Brake Fluid 101

Some automotive engineers believe that there is nothing more important for the safe operation of a vehicle than its brake. The fluid coursing through your car’s internal system is what keeps the system from breaking down. Brake maintenance is an underrated part of car maintenance checks. You ask, “How much brake fluid do I need to keep the system functional?” Keep reading to know.

Think of brake fluid as the electrical impulses your brain fires off to move your muscles. After input is given (like hitting the brake pedal), brake fluid moves through the brake system to the pads and calipers, and the car stops. But how does this fluid work? 

Unfortunately, most drivers do not care all that much about brake maintenance. They only get their brakes repaired once they have failed. Even if you maintain the brake pad regularly, a brake fluid flush is still needed from time to time. Thinking “How much brake fluid do I need?” We have the answer.

What Does Brake Fluid Do?

A car’s brakes are essentially simple. When the driver applies pressure to the brake pedal, the pressurized system of the fluid pushes a piston through the master cylinder, either electronically or mechanically. This in return, sends fluid to the calipers and that pushes the brake pads, latching down on the brake rotor. Thanks to this friction, the speed of the vehicle is reduced.

Different Types Of Brake Fluid

As it is such a crucial safety system, drivers often wonder what they could do to make their cars’ brakes work to the fullest of their potential. We are used to seeing all these “premium” fluids being poured into our cars: special additives and fancy synthetic fluids. In reality, brakes are not all that fancy.

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Most people, only need to replace the fluid regularly to keep the internal system clean. For those who are used to driving on rough terrain where their braking system is subjected to literal torture, a special kind of brake fluid would be better. As for regular drivers, we would consider them overkill.

Let’s go over some of the common fluid types. Keep in mind that you must use what is suggested in the owner’s manual – your best friend when it comes to your vehicle. Mixing fluids isn’t a good idea either which we will get to sometime later.

DOT 3

DOT 3 is generally formulated with an ether-glycol base. The minimum dry boiling point for this one is 401 F, and wet is 205 F. It’s great for the average everyday vehicle used for general purposes, such as commuting.

DOT 4

Similar to the DOT 3 in composition but there are additives in there that raise the minimum boiling point. DOT 4 fluids feature a superior dry boiling point but have to be changed more frequently. They are specifically designed for performance or racing cars that can easily go over the minimum boiling points. They may also be called Super DOT 4 fluids.

Basic DOT 4 is ideal for regular vehicles. If it’s the particular fluid kind, the factory replacement interval will calculate the increased water absorption rate of DOT 4.

DOT 5

Does not go with any other kind of brake fluid. DOT 5 does not attract water, has anti-rust properties, and does not damage the paint. It is also rather experienced but can be outdone by specialty DOT 4 fluids. Feel free to forget about this fluid if your car isn’t specifically designed to operate on DOT 5, or you have a certain reason to run it.

DOT 5.1

The chemical composition of the DOT 5.1 is similar to that of DOT 3 and 4 but it shares minimum dry and wet boiling points with DOT 5. The lower viscosity offered by this fluid is needed by some vehicles. DOT 5.1 is not “superior” to DOT 4 in any way.

How Much Brake Fluid Do I Need In My Car?

Maintaining the optimum level of fluid is always a good practice to ensure the braking system of your vehicle is operating to its fullest capacity. To know how much fluid your car requires at any given time, take a look at the car manual.

The answer should lie between 0.55 to 1 liters (18.60 to 33.81 ounces) of fluid. Drivers who would have lost their car manual or do not even know of its existence may resort to the internet to find these answers. If you are still skeptical, get in touch with the automakers.

When inspecting the level of brake fluid, you will see a guide on the corresponding reservoir, or a warning light will pop up on the car dashboard.

Signs Of Low Brake Fluid

There are some signs that will let you know when the brake fluid of your car has to be refilled. Look out for them:

1. The ABS Light Comes On

Perhaps the most common indicator of something wrong going on with the brake fluid or other braking system bits. Older vehicles might not have the convenient ABS light. Most modern-day vehicles, however, have it on the dashboard. When you see it, know that something is amiss.

2. Problems With Pressing Down On The Brake Pedal

The brake system of your car must respond to every bit of pressure you apply. When the brakes are not properly responding to the pedal, it could be due to low fluid. You also experience that the pedal is softer than when you use it.

How Much Brake Fluid Do I Need

3. Strange Noise When Driving

Noises start emitting from the system when your car is low on braking fluid and you apply the brakes. This is generally caused by a rise in friction in the system. When these sounds reach your ears, you must have the braking system examined as soon as possible or you risk doing more damage to the internal system of your vehicle.

4. Uneven Brake Pads

With the brake fluid level low, the pedals are unable to depress brake pads with the required amount of press. As a result, uneven wear is experienced by the pads. In turn, you hear squealing, squeaking, and grinding once the brakes are applied. The car might also vibrate and rumble when you push down on the pedal.

5. A Burning Smell

A strong odor of something burning comes from the overheated brake fluid. When you smell it, pull over and allow the fluid to cool down. Overheating can be caused by low fluid as the brake system cannot properly circulate the heat produced at the brake pads. The result? Brake failure.

Why You Need To Change The Brake Fluid

DOT 3, 4, and 5.1 brake fluids tend to absorb water from the air around them. Even if the brake reservoir lid is sealed shut, moisture will get to the fluid and contaminate it.

Can You Change Brake Fluid By Yourself?

Yes! Usually, no special tools are required for the job but you do need some level of experience working on automobiles. Go through your vehicle’s owner manual to know about the special requirements mentioned. Make sure you pay extra attention to the kind of brake fluid and brake flushing process. Although not difficult to do, this process has to be done correctly – for your sake and your vehicle’s.

What Is A Brake Fluid Flush?

As you know, we cannot term the brake as a simple mechanism if we think deeply. A lot of parts are working in constant cohesion to ensure you are safe from accidents. Usually, a car features disk brakes in the front along with drum brakes or disk brakes in the back. 

A system of tubes and hoses connects everything together to the master cylinder. The power brake booster, parking brake, and anti-lock system are important parts of the total brake system.

When you hit the brake pedal, the master cylinder is compressed by the plunger. The cylinder then forces the brake fluid to reach the brake at every wheel through the linking hose. 

How Much Brake Fluid Do I Need

At the disk brakes, fluid is pushed to a caliper. The caliper presses the brake fluid against a piston that contracts the brake pads and stops the wheels. At the drum brakes, the wheel cylinder gets the fluid and pushes the brake shoes to stop at the wheel.

This is the entire process of fluid stopping a vehicle. But as the components of the system do deteriorate due to time, dust, rust, and other debris, your brake fluid will not perform as well anymore. This is when you have to perform a fluid flush.

A brake fluid flush is essentially taking all the dirty, old fluid out of the car’s system before replacing it with clean, fresh fluid. This process is needed for every car to ensure it functions properly. So now that you know about a fluid flush, let’s answer, “How much brake fluid do I need for a fluid flush?”

How Much Brake Fluid Do I Need To Flush?

No one wakes up in the morning and expects to find their car down to a broken brake. When that finally happens, you are left wondering, “How much brake fluid do I need to solve this issue?” When a fluid flush can solve the problem, the answer is 500 ml.

For a regular car that runs on a fluid that is nearer to the Min but there is still a lot, 500 ml is enough to bleed a set of brakes (front and back). But this is only applicable in the case that the fluid was not polluted. If the old fluid is somewhat discolored or dirty, we highly recommend flushing out the entirety of the old fluid and replacing it with a new batch.

In this case, you will need about twice as much fluid for the task. As a rule of thumb, you should have your brakes flushed once every 30,000 miles or so.

When changing brake pads, it is crucial that the former fluid is removed so it cannot further contaminate the system. The correct process is to crack the bleed valve open and let the dirty old fluid escape completely before installing new pads. Once the pads are in the proper position, the reservoir has to be topped up. Pump the pedal to seat the new pads, ensuring the reservoir is full at all times.

Amongst the many easy DIY fixes you can perform on your car, changing brake fluid deserves a special mention. The process isn’t difficult per se but does require some tools and equipment to be completed. Check out this video tutorial and our written guide on how to change the fluid in your car:

How To Change Brake Fluid

  • Before you can change the fluid, the system has to be flushed. To do this, get a container where you can drain off the old fluid, a can of brake cleaner, and a wrench.
  • Start by cleaning the main cylinder using the brake cleaner spray. Open it and extract the old fluid. There are two ways you can do this: the pressure bleeding method and the vacuum bleeding method – both equally effective. In both cases, however, you will need to buy a piece of equipment to do the job properly.
  • Once the old fluid has been taken out of the system, fill the cylinder up with the new fluid. Make sure you buy the right one. Brake fluid is categorized according to boiling point.
  • After that, raise the car a little using your jack so you can access each individual brake. You will need an assistant to press down the brake slightly. Once the pedal is pushed, open the brake bleeder valve for the individual wheels in turn and bleed the old fluid into the container. When your help will press the pedal all the way down, shut the valve to stop any excess moisture from seeping into the system.
  • Repeat this seat for every wheel until the fluid runs clear. You might have to go back to fill the master cylinder two to three times.
  • Once you have completed these steps for each wheel, pump the brake pedal 20-30 times to increase the fluid level in the master cylinder.
  • If the brake warning light goes off once you have finished the procedure, pressing down on the brake pedal quickly should solve it.

Is Brake Fluid Flushing Necessary?

Yes, brake fluid flushing is necessary for four very important reasons:

  1. The fluid for the brake is hygroscopic, so it actively attracts atmospheric moisture. This is often considered the primary reason to do a fluid flush. Many parts of your car’s braking system are constructed of metal and flushing the fluid can protect it against failure and corrosion.
  2. With age, brake fluid gets contaminated with pollutants and the boiling point of it goes down significantly. This negatively affected the braking performance, something you are sure to notice after a while. In more extreme cases, the brakes will stop working entirely.
  3. As your traction control and ABS (Anti-lock braking) systems activate, they produce heat, which breaks down the brake fluid further. Although these two systems are necessary parts of the safety system, the heat generated by them does take a toll on the service life of the fluid.
  4. Traction control and ABS parts are sensitive to moisture and little particles from the contaminated fluid. This is why automakers suggest flushing the brake fluid before it can ruin these pricey brake parts. For example, the ABS module is what activates the anti-lock braking system and pulses the brakes to halt the vehicle. This component typically runs for hundreds of dollars.

How Often Should You Change Brake Fluid?

As mentioned above, by the time the braking system of your vehicle goes bad, the brake fluid follows suit. The rubber found in the valves in the master cylinder, wheel cylinders, and calipers deteriorate. Apart from that, moisture can penetrate the system. That causes rust which leads to the formation of unwanted bits in the fluid. 

In addition, the fluid can age and wear out. All this adds up to reduce the effectiveness of a brake system by leaps and bounds.

When impurities jeopardize the quality and service of brake fluid, the engine is put at risk too. Therefore, the fluid flush is super important to keep the car working properly. Do not think twice when your car needs a fluid flush.

It is recommended that the brake fluid be changed every two to three years or 24,000 to 37,000 miles. For the best functioning of the brake system, the fluid needs to have certain qualities as well as meet specific standards. To decide a more specific period, analyze your driving habits. For instance, if you drive a sports car, the fluid should be changed every 3,100 to 6,200 miles because of the obvious operating conditions of the car.

The Dangers Of Water In Brake Fluid

Brake fluid cannot be compressed under pressure. Due to its high boiling point, heat generated by the brakes is not enough to make it boil. However, water has a much lower boiling point. If the brake fluid is contaminated by moisture starting boiling, gas bubbles are created

Gas is compressible. When you press down on the brake pedal and produce hydraulic pressure on the brake system, instead of the force being moved to the brake pads to grip the drums or rotors and slow the car down, it is wasted compressing the gas.

In simpler terms, the brake pedal will simply sink to the floor but the car will not stop. Water in the braking system can also cause rust, blocking narrow passages in the brake hardware or brake lines and resulting in drag – a condition where the brake pads cannot disengage from the drum or rotor, making heat and friction, and maybe even doing more damage.

Fortunately, instead of testing or guessing what the moisture content is, the owner can refer to the manufacturer’s fluid replacement guide. That way, you are confirmed that the fluid inside is clean, effective, and will not let you down on the road.

If your car does not come with a recommended interval, two years is the suggested time. For high-performance vehicles sprinting across the track the time is shortened to six months. For pure race cars, the fluid is replaced after every race. So, the harder you are on the brakes, the more often you will have to replace them.

Sum Up

By this point, you should definitely know “how much brake fluid do I need?” What you must do is make brake checks a part of your routine maintenance to ensure that it is functioning correctly. If not, bring the car to a trusted mechanic.

FAQs

1. Can I Combine Different Kinds Of Brake Fluids?

The short answer is no. Only use the amount that has been recommended. Alter the amount at recommended intervals to prevent issues.

A more in-depth knowledge would be that DOT 3, DOT 4, and DOT 5.1 are compatible (technically). If your car’s brake reservoir is lower than used, you can substitute one for the other in a pinch. However, we strongly suggest not driving for long in that condition – you may get a fluid leak. Bring the vehicle to a mechanic to have the brake flush and refill the system with a clean, fresh (and correct) fluid.

DOT 5 cannot be mixed with any other kind of fluid. The silicone-based formula does not sit well with the other ether-glycol-based formulations. If your car only runs on DOT 5, that’s it – do not put anything else in there as it could greatly damage the brake system. It might be possible to convert your vehicle into a DOT 5 one, but only let a trusted mechanic do it.

2. How Long Do Brake Fluids Last?

Different brake fluids have different service lives. For each DOT:

  • 3: 1 to 2 years
  • 4: 2 to 3 years
  • 5: 5 years
  • 5.1: 3 to 4 years
  • 4+ and DOT 4 SUPER: 2 to 3 years

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2 Comments

  • Daniel Says

    Hi there,
    Question when changing brake fluid should the parking brake should be on, or off? this might cause any issue during the process of changing the brake fluid?

    • I should suggest doing this with the parking brake off. It will not affect the fluids. But Typicallys all brake work is better done with the car in the air and the parking brake off.

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