When maintaining your vehicle’s brake system, you need to regularly monitor the color of your brake fluid. Brake fluid will take some time to go bad when you use the brake system properly. Both vehicle users and drivers must know the color of brake fluid to know exactly when it needs to be replaced.
Brake fluid color varies depending on the type of fluid you are using. Some factors that can cause brake fluid to change color include regular heating, banging on rubber brake lines, moisture, and aging.
Brake Fluid Color Guide
When replacing a master cylinder or brake pad, you need to purchase a bottle of brake fluid. There are three types of brake oil: DOT 3, DOT 4, DOT 5, and DOT 5.1. These brake fluids have different colors. DOT 3, DOT 4, and DOT 5 brake fluids have the same color. The color will change to black or brown over time. The brake fluid color will change due to regular heating, aging rubber brake lines, and moisture. Let us discuss the different brake fluids for automotive in this brake fluid color guide:
DOT 3
The DOT 3 brake fluid is a polyglycol-based product. It was among the first brake fluids developed, but it has lost popularity over the years due to the introduction of more advanced fluids. It has a minimum boiling point of 205 °C. Its wet boiling point is 140°C.
This brake fluid will absorb around one to two percent water, depending on the operating conditions and climate. Brake fluid is best suited for light trucks and domestic cars for normal driving. This brake fluid absorbs moisture from the environment, thus reducing its boiling point. DOT 3 brake fluid is clear and bluish when new. It is well compatible with all other brake fluids, except DOT 5.
DOT 4
This is another brake fluid based on polyglycol. It has a minimum boiling point of 230 degrees Celsius when dry and 155 degrees Celsius when wet. Brake fluid is used in modern, higher- and medium-sized vehicles. It is also ideal for vehicles with ABS, high-speed braking, towing, and high-altitude driving.
The brake fluid also grips moisture, thus reducing its ERPB (boiling point). The fluid can affect the vehicle’s paint, so you need to handle it with care. The color of DOT 4 brake fluid is almost mineral clear, with a slight yellow tint. It is compatible with DOT 3 and DOT 5.1.
DOT 5
This is a silicone-based brake fluid. It has a wet boiling point of 180°C and a dry boiling point of 260°C. It is mostly used on military vehicles and on antique and weekend collector vehicles that sit for a long time. This brake fluid is not compatible with DOT 5.1, DOT 4, and DOT 3.
It does not cause any damage to the paint of your vehicle and does not absorb water. The brake fluid is also compatible with rubber formulations. The fluid absorbs a lot of air, resulting in a poor pedal feel. It is therefore not ideal for racing cars because of its compressibility at high temperatures.
When water gets into the DOT 5 brake fluid, it will cause gassing, freezing, and severe localized corrosion. This is because water is much heavier and does not mix with silicone fluids, making it unsuitable for ABS. This brake fluid is highly compressible under normal braking conditions due to foaming and aeration. This gives you a spongy brake feel.
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DOT 5.1
DOT 5.1 brake fluid is also based on polyglycol. It has a minimum dry boiling point of 270°C and a wet boiling point of 190°C. The fluid is ideal for racecars, towing vehicles, and delivery and fleet trucks. The brake fluid can mix well with DOT 4 and DOT 3. DOT 5 has a higher boiling point than DOT 4 and DOT 3 brake fluids. This fluid also absorbs moisture from the atmosphere, thus reducing its boiling point. Brake fluid can also damage the paint. DOT 5.1 brake fluid is amber in color.
FAQs
What Color Is Brake Fluid When It Leaks?
Brake fluid starts out clear and yellows with age. You might confuse brake fluid with motor oil, but brake fluid has a silkier texture than oil. If you see a silky fluid leaking from the vehicle, then it is most likely the brake fluid. Leaking brake fluid is usually clear or amber. Some causes of a brake fluid leak include problems with the calipers, worn-out brake pads, loose bleeder valves, a leaking master cylinder, and a faulty ABS unit.
How Do You Know When Brake Fluid Is Bad?
There are various signs of bad brake fluid. One is that the brake pedal starts feeling mushy and soft, making it hard for the car to stop. This occurs when moisture builds up in the brake fluid, causing it to boil under the pressure and heat of hard braking and creating air in the brake lines. Another way to tell if the brake fluid has gone bad is by its color. Bad brake fluid is brown or black. The color of brake fluid darkens with age. If you notice that it has become dark, then it is time to replace it.
What Happens If Your Brake Fluid Is Dirty?
Dirty brake fluid can change the operation of your brake system. You will feel this at the brake pedal, and it can help with heat dissipation. On top of that, having moisture in brake fluids can cause internal corrosion of the master cylinder, calipers, and brake lines. This will finally cause damage to the brake system. It is, therefore, crucial to check your brake fluid regularly and replace it whenever it starts to become dark.
Does Brake Fluid Have a Smell?
Brake fluid has a funny, fishy smell, similar to castor or fish oil. Knowing how brake fluid smells can help you detect leaks. Brake fluid leaks near the brake pedal, and thus, you might notice a fishy smell in your vehicle.
What Happens If the Brake Fluid Is Not Changed?
When you fail to change the brake fluid, it absorbs moisture from the environment. Moisture-laden brake fluid can cause corrosion and rust of the metal components. This results in rust particles entering the brake fluid, contaminating it. Failing to change the brake fluid will affect the operation of your brake system.
Check the brake fluid regularly to ensure the braking system is safe. After checking the brake system, ensure the brake fluid reservoir cap is closed tightly. Failing to properly close it can allow grime, debris, and dirt to enter the braking system.
Conclusion
Most brake fluids have a clear, yellowish, or golden color. The fluid’s color darkens as it ages, indicating that it has collected debris and absorbed moisture from the environment. The number of times you change your brake fluid depends on the type of car and how you use the brake system. Check the brake fluid regularly and note its color. Long-term use of bad brake fluid reduces the performance of your car and may eventually damage the braking system and its components. If you cannot do it yourself, get a professional mechanic to check the brake fluid color and change it on your behalf to ensure the car’s safety.
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