Brake Fluid: How to Check Your Brake Fluid? How & When to Change?

In this article, we will learn what is brake fluid, how to change, when to change, and how often brake fluid needs to change. Compared to previous decades, modern vehicles are much more complex. Generally, owners can perform routine maintenance tasks themselves because most manufacturers provide them with simple instructions.

Maintaining your vehicle is probably something that motivates you enough to do certain little things yourself without having to take it to a mechanic every time. Even people without much automotive knowledge and few tools can change their oil and change their air filters. A few minutes and two hands are all it takes to check the brake fluid in almost any car.

Why Do You Need Brake Fluid?

You feel sluggish and irritable after dehydration, making it harder for you to think and move. Your car can also dehydrate after being driven a long distance. 

brake fluid when change how often change brake fluid cost
Brake fluid when change how often change brake fluid cost

Just as your body depends on fluids, your car requires fluids to function properly. These fluids include motor oil, windshield wiper fluid, and brake fluid. If you’re like most drivers, you probably don’t check your wiper fluid or oil all that often, despite the fact that you should.

It is easier than you think to check your brake fluid and it is far more important than you might think. Your safety, the responsiveness of your vehicle, and its longevity all depend on keeping your brake fluid levels at optimal levels. The brake pedal won’t work if you don’t have brake fluid.

Also Read: Types of Cars

Define Brake Fluid

Hydraulic Fluid, such as brake fluid, runs through the brake lines that lead to all four wheels of your vehicle. When you press down on the brake pedal, the brake fluid causes to be applied to the brakes so you can slow down & stop your car.

During Braking, the force is transferred from the vacuum-powered booster to the brake pads, which finally press against the wheels and bring the vehicle to a halt.

It is important, therefore, to maintain the high quality of brake fluid. Moisture, which is inhaled through your car’s exhaust, will degrade your fluid’s performance. Ultimately, this may negatively, affect your vehicle’s braking.

Brake Fluid must force to move throughout the brake system when the brake pedal is applied because brake fluid, like other hydraulic fluid, is non-compressible.

What is Brake Fluid Corrosion?

It is not the brake fluid that corrodes, but the hydraulic additive package that is part of the brake fluid that corrodes, leading to corrosion of internal hydraulic components. The brake fluid as a whole doesn’t corrode, but when the additive package breaks down, the brake fluid is no longer equipped with adequate corrosion inhibitors for internal hydraulic components.

Also read: Types of bikes

Define Brake Fluid Flush Scheduling

Like dynamically your oil and exchange your car’s air filters, once to schedule a whole Brake Fluid Flush to depend not only on your driving habits but also on your car’s year of making and model number. Most makers advocate this service each a pair of years or 30,000 miles, although this may vary so you can consult your owner’s manual to make sure. Also, grasp that this can be simply a guideline. The only way you can be sure is by checking the quality of your car’s brake fluid with an appropriate test kit or consulting a professional mechanic.

Function of Brake Fluid

When you press on the brake pedal, brake fluid delivers the force of your foot into pressure on the brakes of your vehicle. Hydraulic braking systems use this liquid chemical solution.

During braking, extreme heat is generated that causes moisture to condense in the brake hydraulic system. Brake fluid absorbs this moisture, protecting it from boiling over and causing brake failure. Moreover, brake fluid lubricates moving parts of the braking system and prevents corrosion.

Tests measure how long brake fluid will remain liquid at low temperatures and how long it will resist boiling at high temperatures. The fluid must also be compatible with other brake fluids and parts of the braking system, and it must effectively prevent corrosion.

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Workflow of Brake Fluid: How Does Brake Fluid Work?

Before you check on brake fluid, you must know the workflow concept of the brake fluid. Otherwise, it will create a mess in your brake system or damaged while changing braking fluid on your vehicle.

  • First, the force from your foot is increased by a vacuum booster simply behind the pedal. This increased force activates the master cylinder, which pushes pressurized brake fluid into the brake lines. The more durable you endure the brake pedal, the lot of pressurized the fluid becomes, which will increase the stopping force applied by the brakes.
  • From there, the brake fluid flows through the brake lines till it reaches the caliper on every wheel. At that point, the pressurized fluid forces a group of pistons to push the restraint against a spinning rotor.
  • This works as a result of liquid including brake fluid is incompressible, which means it will act as a solid force below pressure, albeit it moves sort of a liquid. Once the restraint rubs against the rotor, the friction causes the wheels to slow and eventually stop.
  • Impressively, all of this happens within the blink of an eye. Nonetheless, if your brake fluid has gone unhealthy or is just too low, your brakes won’t be as responsive, or worse, they will not work all. That’s why it’s crucial to own your brake fluid habitually checked.

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Bosch ESI6-32N Brake Fluid (Direct Replacement for DOT 3, DOT 4, and DOT 5.1) - 1 Quart
  • High compatibility. Use with or direct replacement for DOT 3, DOT 4, and DOT 5. 1
  • Extended Service Interval (ESI): Lasts 100% longer than DOT 3, 50% longer than DOT 4, and 10% longer than DOT 5. 1
  • Exceeds all DOT 3, DOT 4, and DOT 5. 1 standards
  • Wet boiling point ~ 365 DegreeF/Viscosity at -40 DegreeC ~ 685mm2/s
  • Standard brake fluid has a recommended change interval of 2 years. The recommended change interval for Bosch ESI6 is 3 years.

Characteristics of Brake Fluid

Constant Viscosity

The viscosity of a liquid indicates its thickness and ease of flow. The viscosity of the brake fluid must remain constant across a wide temperature range, as the fluid must deliver the same performance regardless of the level of temperature. It is of particular importance for anti-lock braking systems (ABS) or traction and stability control systems, as these systems use micro-valves and require rapid activation.

Low Compressibility

A liquid’s compressibility refers to its ability to shrink under pressure.  In contrast to the highly compressible nature of sponges, the brake fluid must maintain a low level of compressibility.  The hydraulic pressure generated on the brake rotor may not be applied consistently if the brake pedal feels inconsistent.


Due to its corrosive properties, pure brake fluid is usually accompanied by corrosion inhibitors in commercial brake fluid. As moisture enters the brake system, this prevents corrosion in brake parts like the caliper or master cylinder. Depending on the manufacturer, the additive package may not only contain corrosion inhibitors but also include anti-wear and anti-foaming components.

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High Boiling Point

To withstand such high temperatures, the brake fluid needs a high boiling point.

Two types of brake fluid boiling points exist: one is a dry boiling point for fresh brake fluid; another is a wet boiling point for brake fluid that has absorbed some moisture.

As new brake fluid has a higher boiling point than the boiling point of dry brake fluid, the dry boiling point is always higher. After some moisture contamination, the wet boiling point is what is expected to be.

The brake fluid will vaporize into gas if the temperature exceeds its boiling point, reducing its ability to transmit hydraulic pressure and decreasing braking performance. Because brake fluid usually evaporates more quickly in extreme temperatures when it is old, it is likely to have a lower boiling point due to moisture exposure.

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ATE Original Super DOT 5.1 Brake Fluid, 1 Liter Can
  • Fast reaction time, ideal for ESP, ABS and ASR systems
  • Boiling points and viscosities that are better than in statutory and technical regulations
  • Ideal for all applications with top performance in hot as well as cold conditions
  • Protection from corrosion by high-grade additives
  • Meets all OEM requirements

Key Signs of Low Brake fluid

Oily Puddle

The brake system may be leaking if you see a small puddle of oily liquid under your car. Master cylinder, rubber hoses, around the calipers are the several places where brake fluid can leak.

Unusual Activation of Anti Braking System (ABS)

You activate the Anti braking system (ABS) when you are slowing down on slippery roads or avoiding skidding. However, if you activate the anti-braking system while you are rolling your car’s wheels on a dry road, then you should have the brake fluid and system inspected. You need to have the brake fluid topped up by a trained mechanic from a reputable automotive shop if you notice this.

Warning Lights

It is an indication that the brake fluid in your vehicle is insufficient for transferring power to the brakes if you see warning lights of the brake system on. Immediately take your car to a mechanic to inspect for brake leaks and fix them if you see this sign.

In the event of a leak, the expert can seal the leakages and replace the components if the leakages are hard to fix. One of the main components of the brake system is the master cylinder, which has hoses and lines connected to the master cylinder.

Increased Stoppage Distance

As the brake pads begin to wear out, the pistons in the caliper have to move out farther in order to apply the brakes, potentially causing low brake fluid levels. In addition to increased stopping distances, worn-out brake pads can also affect braking performance. A grinding noise can also be heard from the brakes, which results from rubbing up against the rotors as the brake pads wear down.

Brake Pads and pedals Issue

Symptoms of low brake fluid include difficulty engaging the brake pedal, brake pads vibrating during braking, and hard to engage the brake pedal. If you experience any of these symptoms, you should replace the brake fluid immediately.

Low Reservoir on Brake Fluid

If you notice a low level in the brake reservoir, this is likely a sign of low brake fluid. Check your car’s brake fluid often to ensure there aren’t any leaks or other problems with the brake system.

How to Inspect Brake Fluid Reservoir?

Proper Location of Brake Fluid Reservoir

Your vehicle’s brake fluid reservoir is on the driver’s side. It is usually located near the firewall near the brake booster. To check the brake fluid, you must find the reservoir. On the brake master cylinder, just in front of it, is the brake fluid reservoir, typically a plastic container.

A plastic reservoir is not available in an older vehicle; you must remove it to check the level of fluid by removing a little metal box which is known as a master cylinder.

Adding Brake Fluid

It doesn’t matter how old your vehicle is, you should add the brake fluid is low. If your vehicle has dual reservoirs, you should fill both to capacity. Wipe away any spilled and excessive brake fluid immediately. Please note that if your reservoir is empty or too low, it indicates a problem with your brake system. Consult a mechanic as soon as possible, as your vehicle may be unsafe.

Finishing Touch

You can check continuously the brake fluid’s quality by opening up the reservoir cap. Otherwise, you are finished checking the brake fluid of your vehicle.

Brake Line Checking

If the fluid level in your piston chamber remains full, you ought not to check your brake lines. However, if you’re losing brake fluid, you would like to ascertain a leak within the wheel cylinders or the brake lines.

The best thanks to check brake lines are to place the vehicle au fait a hydraulic hoist, raise it over your head, walk underneath it, and examine the lines as they lead from the hood space to every wheel. Leaks are also coming back from holes in the lines wherever the steel lines become rubber ones or where the brake lines connect with the wheel cylinders.

  • Take extra care when inspecting the brake lines.
  • Wetness and streaks of dried fluid indicate a problem.
  • Rust spots on your lines should be gently sanded off.
  • Additionally, check under those spots for thin spots that may develop into holes over time.
  • Since the rubber components of the brake lines.
  • The rubber should become sticky, soft, spongy, or worn when these conditions occur.
  • They are supposed to last as long as your vehicle, so they should never need replacing.
  • A professional can tell you if they should be replaced if they look very bad. If the brake lines look very bad and the vehicle is relatively new, go back to the dealership and ask them to replace the lines for free.
  • You can look at the inner surfaces of your tires.
  • The leaking wheel cylinders are indicated by dripping.

Efficiency Issue & Solution of Brake Fluid

Brake Fluid Issue#1 Spongy Pedal Issue

Typically, brake fluid leaks cause this car brake response problem. Damaged brake hoses can also cause leaks or ballooning of the hose, which can cause brake inefficiency.


  • Check for chafing, cuts, deterioration, and leaks regularly.
  • As soon as the vehicle has been lowered, make sure it is not bent or twisted, that the correct tightening torque is applied, and that no other suspension parts are in contact with it.
  • Brake hoses should be flexible and durable with low moisture permeability as well as low volume expansion under pressure.

Brake Fluid Issue#2 Vapor Lock Issue

Hydraulic brake fluid is also hygroscopic, which means it absorbs water over time. As brake fluid absorbs moisture, its boiling point decreases, which is why it may be necessary to replace it sooner rather than later.

As a result of evaporating brake fluid, vapor lock is a potentially dangerous occurrence. Brake fluid is designed with a high boiling point to combat the heat generated when you brake.


Brake Fluid Testing

Regular brake fluid inspection is fundamental. The only way to know if the fluid is in good health is to test it. This can be accomplished using a pen-style tester that measures moisture content electronically in seconds. Other, more accurate brake fluid testers that use industry-standard methods give better readings with this method.

Pressure Checking

Using a pressure gauge attached to the closest caliper brake pipe, perform a leak pass test for the master cylinder by pressurizing it to 50 bars for 45 seconds. Any pressure loss beyond 4 bars must be recorded during this time. It is also possible to perform a second check, at a pressure of 10 psi, if the drop is larger, indicating a master cylinder leak.

Types of Brake Fluids & Colors

Dot 3

A study by the Society of Automotive engineers found that DOT3 brake fluid can absorb 2 percent of its volume in water every year. If you expose the brake system to excessive moisture for a long period of time, you will experience issues like vapor-lock or spongy pedals.

Dot 4

Fluids Dot 4 and Dot 3 are interchangeable, but it’s best not to add DOT 3 to the systems that already use DOT4. It’s the preferred fluid for vehicles, as it’s designed for all vehicles and has a higher boiling point than DOT3.  

Dot 5

DOT five typically noted as artificial brake fluid is silicone-based, which suggests it doesn’t absorb any moisture. Several street mechanic would use synthetic as a result of it is not corrosive to other brake parts & its color that create it nice for conserving classic cars for long periods of time. 

However there are some drawbacks to silicon-based fluids, they expand a lot once compressed, which may make the pedal feel spongy, conjointly DOT 5 fluids can’t be mixed with the other variety of brake fluids. DOT 5 can typically have a violet tint in color to differentiate it from DOT 3, DOT 4, and 5.1 fluids.

Dot 5.1

DOT 5.1 may be a non-silicone-based poly glycol that incorporates a boiling purpose of over five hundred degrees. In contrast to DOT 5, DOT 5.1 will be mixed with DOT three or DOT 4. Also, DOT 5.1 can sometimes have the very best-rated boiling point that is best counseled for severe duty and superior applications.

Problems and Solutions for Brake Fluid

How to bleed brake fluid with drum brakes?

If your vehicle is left- or right-hand driven, always start bleeding the brakes with the caliper furthest from the master cylinder.

  • To start, the manufacturer’s specifications should be followed when adjusting the brake shoes-to-brake drum clearance.
  • The bleed nipples in all-wheel cylinders should be closed, so fit a bleed pipe to the bleed nipple of the wheel cylinder the furthest from the master cylinder.
  • The brake fluid should be visually clean and clear of air bubbles after using slow, full, and firm strokes on the brake pedal.
  • Remove the bleed pipe from the nipple and tighten the bolt while holding the pedal fully depressed. Repeat the process for the opposite rear wheel cylinder.
  • Bleed the front calipers starting with the furthest and bringing them closer to the master cylinder after bleeding the rear wheel cylinders.

How to bleed brake fluid with front and rear disk brake?

  • Fit the first caliper with a bleed pipe and loosen the nipple with all bleed nipples closed.
  • As you bleed the brakes, continue to pedal slowly, fully, and firmly until the brake fluid is visible and clean.
  • The bleed nipple should be tightened and the bleed pipe removed with the pedal fully depressed.
  • Repeat the procedure on the other rear caliper.
  • Then, following the disassembly of the rear calipers, ensure that the front calipers are also properly operating and free of air bubbles. To do this, gradually bleed both the front and rear calipers from further away to closer to the master cylinder.
  • The last step is to ensure adequate pedal pressure.

What is the basic problem of brake fluid?

There are different types of brake fluid problems today than 20-30 years ago, as moisture seeps into the brake fluid. Nowadays, moisture in brake fluid is not much of a problem because modern brake hoses are constructed in a way that prevents moisture from entering the fluid.

The most common cause of brake fluid problems is copper dissolved in the fluid, and the additive package in the fluid has depleted. Brake fluid can therefore be accurately tested to determine whether it needs replacing.

Whenever the additive package of brake fluid is depleted, an internal brake system component corrosion and sludge buildup may result. Copper levels in brake fluid are an indication of brake fluid’s additive package’s health.

When you think about changing the brake fluid?

A typical rule of thumb is each one or 2 years, however, that may depend upon the advice of your vehicle manufacturer.

The foremost common threat is wetly absorbed from the air. Water within the brake fluid will lower its boiling point, which will tend to cut back pressure at intervals in the braking system and hurt performance for the explanations mentioned above. In addition, moisture can begin to corrode a number of the braking system’s different components. 

As brake fluid ages, it tends to travel from clear or light-brown to a darker color. Wet contamination will sometimes have a constant effect, thus cloudy-looking brake fluid could also be an indication it’s time to urge it replaced. And you’ll be able to have knowledgeable check your fluid’s wet content at any time.

Alternatives of Brake Fluid

Some people siphon diesel and use it as brake fluid oil since brake fluid has almost the same viscosity as diesel. Unfortunately, this almost always ends in disaster since diesel and most petroleum products usually destroy the seals in brake pads.

Therefore, if you think that diesel or any other petroleum-based product can be used to replace brake fluid, you should cease immediately. Water and soap are the best emergency brake fluid substitutes since they are easy to prepare. Water and soap are the easiest emergency brake fluid substitutes.

You can find water and soap in the first house you see along the highway if you are in the middle of nowhere. If you start walking, you will probably find soap and water in your car or house. If you cannot find water and detergent, you may substitute radiator water alone.

How to Make and Use Soap Water as a Substitute?

It is very important to make sure you are the only one left with no other option before using a soap and water solution as a brake fluid alternative.

It is therefore advisable to get real brake fluid if at all possible. You are off-grid & very far away from civilization then you need to use a soap and water solution.

Old Brake Fluid Oil Removal

It is common to find brake fluid in the system. You can remove all of it before you make and introduce your brake fluid substitute. If you can, flush it out.

Cleaning up the old fluid is essential to avoid any possible interaction between the oil and the water or soap solution you will be introducing. Such interaction will most likely negatively affect your brake system.

Add Mixture of Soap & Water

The soap water mixture is all about 40 percent detergent and should be mixed with 60 percent water. When you have mixed the two, shake them thoroughly to ensure the solution has been thoroughly mixed. Add the soap and water solution to the brake fluid reservoir just as if you were adding normal brake fluid. 

Do not over use brake too much

You should only use your brakes sparingly if you use a soap and water solution. It is important not to overheat the system or the solution. The solution should be flushed out when you get back to civilization at a reputable repair shop to make sure that your brake system is not damaged.

Tips for Brake Fluid

Checking Brake Fluid Reservoir

It’s almost as easy to check the brake fluid level of your car as the windshield washer fluid. You don’t need any special skills if you can open the hood of your vehicle and remove the cap. Before you begin, please be aware that brake fluid can be highly toxic. After checking the brake fluid level, wash your hands thoroughly and avoid getting it in your eyes. Also, it can cause corrosion on the finish of your vehicle or engine components. 

Are the brake fluid Hygroscopic?

When driving your vehicle, your restraint can reach very high temperatures and this heat is then passed onto the brake fluid which might raise the fluid temperature to over 200°C. once the fluid gets too hot, little air bubbles begin to make because it begins to boil, and since air is a lot of compressible than fluid, the danger of a spongy pedal increases.

If the fluid is repeatedly heated past its boiling point, eventually the brake pedal can travel all the thanks to the ground while not providing a lot of force on the brake pads, which means you will struggle to tug up at intersections. this can be referred to as brake fade.

What are the warning Signs of Brake Fluid

Your vehicle should not lose brake fluid during normal operation. The level may drop slightly over time as the brakes wear. But if the level has dropped significantly since your last fluid level check or full service, it’s time to see a mechanic. Easier and cheaper to repair than in the future with total brake failure.

Can you check brake fluid on your own? 

A trained Mechanic is better equipped to change your brake fluid than a do-it-yourselfer.  Old fluids need to be completely drained from the system, and it’s a delicate material that needs to be handled with care.  A glycol-based fluid must not be mixed with silicon-based fluid. Mixing the two will result in the deterioration of the latter.

Frequently Asked Questions on Brake Fluid

What is the meaning of DOT?

DOT is a short form for the Department of Transportation, which defines safety regulations regarding different brake fluids. The Department of Transport (DOT) gives all forms of brake fluid a rating. Wet and dry boiling points are used to assign DOT ratings to the brake fluids.

What is the color of Brake Fluid?

The brake fluid in a healthy car should be nearly clear and have a yellowish tint, which is pretty close to the color it was in the bottle before it was poured into the reservoir.

Does the Brake Fluid Smell?

There can be a leak in the middle or rear wheels when the brake fluid is clear to light yellow and darker as it ages. Brake fluid smells like fish oil. Brake fluid is slicker than engine oil.

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