What color is the fluid that runs through your braking system? What does that fluid do? What makes it change color? If you have ever asked yourself these questions about the braking fluid in your car, you’ve come to the right place. Read to find out all you need to know about brake fluid.
Brake fluid (view on Amazon) is a type of hydraulic fluid designed for use in the brake system that is stored in the brake lines and the master cylinder reservoir. The brake fluid facilitates the brake pedal movement which actuates the brakes at the wheel to stop the car. It also serves as an anti-corrosion lubricant. Brake calipers (view on Amazon) hold the brake pads (view on Amazon) in place. The calipers and the fluid are major components of the hydraulic system along with the brake fluid. Brake fluid presses the pistons and the brake pads together, which stops the wheels and rotors.
The brake shoes are a part of the brake drum and they push kinetic energy to thermal energy. The brake drums and shoes generate friction to support the stopping or slowing down. When the gas pedal is depressed, the brake boosters increase the applied pressure. A plunger inside the master cylinder pumps the brake fluid through break lines to the brakes. The brake fluid provides the pressure for the brake pads, which is increased by the booster.
What Color is Brake Fluid?
New brake fluid looks very similar to new motor oil and it is most commonly transparent with a light yellow or gold hue. However, DOT 3, 4, 5 and 5.1 brake fluids all have different colors when unused. This also includes the brake fluid in the reservoir. DOT 3 brake fluid is poly glycol based with a dry minimum boiling point of 205 degrees Celsius and a wet boiling point of 140 degrees Celsius.
When unused, the DOT 3 brake fluid has a light bluish hue. DOT 4 brake fluid typically has the transparent color with a light yellow or gold hue. DOT 4 is poly glycol based with a minimum dry boiling point of 230 degrees Celsius and a wet boiling point of 155 degrees Celsius.DOT 5 brake fluid is silicone-based with a dry boiling point of 260 degrees Celsius and a wet boiling point of 180 degrees Celsius. DOT 5.1 brake fluid is also poly glycol-based and has a light amber hue. The DOT 5.1 has a wet boiling point of 190 degrees Celsius and a dry boiling point of 270 degrees Celsius
As the brake fluid is used, the yellow or gold hue turns toward brown, the light blue turns to a dark blue, and so on. Old brake fluid which hasn’t been changed for years can turn a thick dark brown, resembling old motor oil. The old fluid will continue to become darker until it turns black. The cause of the color change is a continuous collection of debris, water, and grime. Brake fluid in this condition can harm the brake calipers and master cylinder seals to deteriorate.
How Long Does Brake Fluid Last?
Brake fluid is not designed to last for the lifetime of your car. However, for the first year or two, the fluid should come out clear with a small tint of color. When the copper content reaches or exceeds 200 PPM, the brake fluid requires servicing. The additive package is renewed during the servicing. When the fluid is not healthy, it causes big problems in the braking system.
Over time, the brake fluid loses its moisture resistance which means it has begun to absorb water. Air even sometimes becomes trapped inside the brake fluid. To remedy these problems, your brakes should be serviced based upon the manufacturer recommendation to flush the brake fluid.
What Causes the Color of Brake Fluid to Change?
The color of brake fluid changes with time and the condition of the fluid. Temperatures, pressure, time, and contaminating particles all affect the color of the brake fluid. The small hint of yellow will become a more solid gold. The fluid loses its transparency. Here are the most common causes of brake fluid color change:
Wear and tear – Brake fluid works hard, traveling through the brake system as you continuously pound on the brakes. When the brake pedal is depressed, the plunger in the brake master cylinder pumps the brake fluid through break lines to the brakes. The brake pads squeeze on the brake discs or the brake fluid pressure pushes the brake shoes to the drums. The brake fluid travels and also serves as pressure for the brake pads. As a vehicle is continuously driven and accumulating miles parts eventually wear out. This includes the fluids, which the continuously used brake fluid changes color and loses some of its features. Is also includes the brake pads that peer out from behind the wheels. Lastly, the materials used to make the parts affects the life cycle.
Algae – When algae gets into your brake fluid, it turns the brake fluid green. The transparent fluid reflects the color of the algae. When the fluid turns green, it is a sign that the brake fluid needs to be flushed.
Lack of maintenance – Routine maintenance is a good way to prolong the life of the braking system. The brake fluid can be inspected when the car goes in for an oil change. When a vehicle is not serviced regularly, things build up. The bore inside the master cylinder can become corroded, which results leaks in the seals. It can be observed that the color of the brake fluid in the reservoir is no longer a vibrant color. When the rubber seals on the brake master cylinder become worn, the brake fluid can also become worn. The brake pressure is also affected by the worn seals. When either of problems arise, the brake fluid goes bad and turns to a darker color.
The braking system should be serviced routinely according to the manufacturer specification. The fluid should be flushed periodically to get rid of air, water, and contaminants. If the vehicle is not being serviced as recommended, the brake fluid will eventually leak out of certain components. Namely, the brake master cylinder rubber seals wear out and need replacing. The worn seals affect the brake pressure.
Heavier vehicles require more action to stop them as compared to small vehicles. Since the heavier, industrial vehicles require more to slow down or stop, the brake pads and brake fluid are constantly overworked and will have to be serviced more often.
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Low brake fluid – Maintaining the correct amount of fluids is one of the most important aspects of automobile maintenance. Brake fluid is one of those that must be clean and abundant. High temperatures with low boiling points cause brake fluid issues due to the extreme heat. Worse of all, brake fluid leaks also affect the level of fluid running through the system. Not only will leaks cause the amount of brake fluid to drop, so will worn brake pads. The more the brake pads wear, the brake fluid in the reservoir becomes displaced. More fluid is required to push the pads to the brake disc. When the braking system does not have enough fluid for whatever reason, problems arise.
Brake fluid leaks – The amount of brake fluid running through the system is influenced by many things. The vale and piston seals which lie inside the brake master cylinder start to leak after a vehicle has been driven for so many years. The brake fluid also absorbs water through air over time. The flat sealing washer becomes hardened and no longer seals. The bore inside the brake master cylinder becomes corroded which causes leaks in the seals. The color of the fluid in the reservoir is no longer a healthy color. In these cases, the leaks can be identified and the seals can be replaced.
Contaminated brake fluid – When the brake fluid gets dirty, it turns to a darker color.
Brake fluid becomes dirty and contaminated from a few sources. When the brake pedal is depressed, the created force transfers to the brakes by using brake fluid. When the rubber seals on the brake master cylinder wear out, the brake fluid can become contaminated.
Bad driving habits – The amount of abuse placed on the brakes affects the life cycle of the braking system parts. In the case of a very aggressive driver, the rough handling is placing more strain on the brakes than necessary. High speeds, sudden turns and stops over a long period of time will wear the brake pads out prematurely. The brake shoes stick against the wheel drum. By going easy on your brakes, your car is less likely to develop leaks and part failures. That way, you can prevent future problems with your braking system and get much more life out of your car.
Symptoms of Brake Fluid Problems
Many car owners don’t make a habit out of checking the brake fluid. Yet, when your brake fluid is dirty or contaminated, there will be signs in your vehicle’s performance. Here are the most common symptoms of brake fluid that has gone bad:
Brake warning light – Modern cars are equipped with a brake warning light on the dash. The brake warning light activates when the brake fluid is low in the reservoir or there is a leak, the brake pads are worn, or the brakes need to be replaced. The warning light will also activate when the brake globe is burnt out or failed, a sensor has failed, or when brake master cylinder has issues.
Puddles of brake fluid – If you see a puddle of brake fluid on the ground under your car after you drive, that is confirmation that there is a brake fluid leak. The car is not safe to drive in this case. However, new brake fluid looks a lot like oil and transmission fluid. If you are not sure whether the fluid is brake fluid, let a certified mechanic have a look.
Spongy brake pedal – When you press the brake pedal to slow down or stop, the pedal can feel spongy. Your brakes still work; however, using them requires more work. The spongey feel when you press the brake means there is a brake fluid leak, the brake pads need to be replaced, or the brake master cylinder is having a problem.
Driving a vehicle where the brakes could possibly fail is very dangerous. If the brake fluid is low, or dirty, have the system flushed right away. You may be able to flush the system yourself. If you can’t, a professional will charge you around $100 to flush the old brake fluid and replace it. Get that brake fluid replaced and get back on the road safely.