Why Does Brake Fluid Turn Black?

Brake fluid is an essential component of a vehicle’s brake system, helping to transfer the pressure applied to the brake pedal to the brake pads and rotors. However, over time, brake fluid can become discolored and turn black.

In this article, we will explore the various reasons brake fluid can turn black, including contamination by oil or other substances, absorption of moisture, and heat and friction during standard braking.

Understanding the causes of discolored brake fluid can help you keep your vehicle’s brake system in good working order and ensure that you can stop safely. Brake fluid can turn black for a few different reasons.

1. One possible reason is that it has absorbed moisture from the air. When brake fluid absorbs moisture, it can become contaminated, leading to several problems, including reduced braking performance and corrosion in the brake system.
2. Another possible reason that brake fluid can turn black is that it has been contaminated by oil or other substances. If brake fluid comes into contact with oil or other contaminants, it can become discolored and may not function properly.
3. Finally, brake fluid can turn black due to the heat and friction that occurs during normal braking. When the brakes are applied, the brake fluid can become hot, which can cause it to break down and become discolored over time.

In general, it is essential to keep an eye on the color of your brake fluid and replace it when necessary to ensure that your brakes are functioning properly. If your brake fluid is dirty or discolored, it is a good idea to have it checked by a mechanic to determine the cause and take the appropriate action.

What Does Brake Fluid Do?

You probably haven’t changed the brake fluid on your car in a while if you’re wondering if it’s too old. It is perfectly normal to experience this. It is designed to last for a long time, after all. 

If your brake fluid appears brown or black, you should consider changing it if it is black or dark. Fluid pressure is necessary for hydraulic brakes to function effectively in modern cars. 

In disk brakes and drum brakes, the master cylinder and brake booster work together to produce pressure for the moving parts of the brake to function. The fluid pressure must be just right for the brakes to squeal or push into the brake drums to stop and slow down.

Understanding Why Brake Fluid Turns Black

The brake fluid in your car might not be something you think about often, but it can be an issue if the pedal feels soft. It helps your brakes function at the right pressure when using the right brake fluid.

The brake fluid’s quality changes when it’s contaminated or old. You should be able to tell after a quick inspection what your local mechanic should do.

You should be aware that very dark colors indicate that your fluid has been contaminated significantly and absorbed moisture. As a result, the brake system cannot build pressure, compromising your braking ability.

It might feel like your brake pedal is spongy or softer than usual. You may have to pump the pedal several times to work properly in serious situations.

It is recommended that fresh brake fluid be relatively clear, if not slightly golden, in color. In general, this applies to all types of brake fluid.

With time, brake fluid becomes contaminated. It shows aging brake fluid when it darkens and turns black or brown. Contamination of brake fluid can occur in many ways.

Deteriorating Fluid Hoses:

A rubber fluid hose may deteriorate into fluid if it is not maintained. There will come a time when the rubber brake lines on your car will need to be replaced because of deterioration.

In addition to being corrosive, brake fluid also dissolves the lines, so while they are designed to withstand corrosion, eventually, they will fall apart.

Additionally, it can darken due to microscopic rubber pieces and chemicals that leak into the fluid from the lines.

Normal Heating:

A natural result of brake fluid heating up is that it will darken. By contacting the calipers, brake fluid is heated, causing a chemical change in the fluid, joining moisture and other contamination to create darkening.

Normal Aging:

When the brake fluid is not maintained properly, it darkens naturally over time as it becomes contaminated. If your brake fluid hasn’t been changed in too long, it will most likely look brown or black because of normal aging. Darkening and reducing its efficiency are caused by contaminants collecting in the fluid.

Moisture Contamination:

Brake lines can be heated to the point where moisture boils, causing the fluid to darken and air to enter the hoses. There is a possibility that brake fluid will absorb moisture from the surrounding air. It usually occurs as a result of leaks in rubber brake lines.

As brake fluid accumulates moisture, a couple of problems can result. In calipers and drums, water can reach incredibly high temperatures because it has a much lower boiling point than brake fluid.

During the boiling process, the water is converted into steam, which darkens the brake fluid and introduces air into the lines. As a result, the brake pedal can feel soft, or you may need to pump it to get it to work properly.

When Should I Get An Inspection If My Brake Fluid Is Black Or Brown?

When you notice discoloration in your brake fluid, you should have an inspection performed as soon as possible. You may not immediately perceive it as a huge problem.

If your brake fluid goes bad, your braking system may be severely affected. You can discover discolored brake fluid by looking out for these signs:

• There is a long reaction time when you apply the brakes
• Slowing down is difficult
• When braking, your car skids
• Changing gears is hard

Is It Bad If Brake Fluid Is Black?

If the brake fluid is black or brown, it’s usually a bad sign. You probably haven’t used your brakes for too long since the master cylinder reservoir is filled with contaminants. It should be fine with a quick fluid replacement, though.

You should replace your brake fluid regularly before it turns brown or black. Whenever your fluid is exceptionally dark, it has collected a significant amount of contamination and absorbed moisture.

What Inspection Do I Need If My Brake Fluid Is Black Or Brown?

If your brake fluid is black or brown, you should check it immediately. You may notice that your car’s brake fluid becomes discolored and contaminated over time, especially if it has not been serviced regularly.

It is usually enough for a mechanic to replace the fluid, and your car will be good to go! Occasionally, the brake system can be damaged, which requires a more thorough inspection. You shouldn’t worry about spending too much since a brake fluid change is only $100.

When To Replace Brake Fluid?

Regularly changing the brake fluid on your vehicle is recommended. If it turns brown or black, it should be removed immediately.

There is a high likelihood of brake fluid becoming black or brown if it has been heavily contaminated. The brake system’s ability to build pressure is diminished when this occurs, and the brakes may perform less well.

If your brake fluid is contaminated, you could have spongy brakes. It may even be necessary to press brakes more than once for them to function properly in particularly dire situations. It is a serious sign that the brake fluid needs to be replaced.

How Important Is It That Your Brake Fluid Is Functioning?

When you drive, you need working brakes, and brake fluid is integral to them working. A slight change in braking effectiveness can put you at risk-especially on a busy highway. As a result, you should try to avoid accidents before they occur and call your local mechanic as soon as you notice discoloration.

Tips For Maintaining Brake Safety

Even though brakes are an essential component of your car, they should be treated with care. Brakes wear out over time, which is something to keep in mind.

Ensure that your brake fluid is at the correct level, and service your car regularly to prevent this. Additionally, if you are driving a manual vehicle, make sure you shift gears carefully and avoid braking too quickly.

How To Avoid Brake Fluid Contamination?

Avoid contaminating your brake fluid by buying only a small bottle if you plan to top up your own brake fluid. When you fill up your brake fluid cylinder, throw away the remaining fluid since air can contaminate the fluid. This will happen even if the cap is put back on very quickly.

Final Words

High temperatures combined with moisture invasion cause rubber (EPDM) to dissolve due to fluid breakdown. The suspended carbon from both sources causes the black color.

When the fluid is black, serious damage to the system has already occurred. Make sure to change your brake fluid before it darkens. In addition to changing your car’s oil, the brake fluid should also be changed.