Maintaining a brake system in your car requires monitoring brake fluid color on a regular basis. Brake fluid is not something you should have to be replacing regularly, especially if you are using your brake system properly. But even with standard brake use, brake fluid goes bad every couple of years.
So, what do you need to look for when checking your brake fluid? Here’s a guide to brake fluid and what its color is telling you.
What Color is Brake Fluid?
Brake fluid looks like motor oil. So, if there is fluid leaking out of your car, distinguishing between the two can be very tough. The key to determining you are leaking brake fluid is the slippery texture, the see-thru nature of the fluid (well, at least it should be), and the color.
And for anywhere from 2 ½ to 5 years, your fluid color should stay clear. And if it maintains a clear, yellowish tint, your brake fluid should be in good shape.
The Standard Life of Brake Fluid
The reservoir of your master brake system holds brake fluid. Fluid also runs through the brake lines between your master cylinder and your wheels. If you press down hard on the brakes frequently, your fluid will contaminate quicker than it should.
But even with regular brake use, your brake fluid will pick up contaminates over time. The brake fluid will absorb moisture. Microscopic pieces from the rubber breaks lines will get in there as well. Standard heating and aging also cause the brake fluid to turn as well.
When your brake fluid first starts aging, the color of the fluid will shift from yellow to gold. The fluid usually stays clear at this point, so it should still perform at a strong level. But the next phase, the warning phase for your brake fluid, is inevitable.
Beware of the Green Fluid
Green brake fluid is the first sign you need to consider changing your brake fluid. Now, sometimes the green color is simply because some algae made it into your brake fluid. If the fluid is green but clear, it might still work. But green brake fluid is the first sign your fluid needs to be replaced.
From green, as your brake fluid becomes more contaminated, the color will shift to brown and then black. If your brake fluid is black, then you are well past the point of needing to change your brake fluid.
How to Know if You Have Dirty Brake Fluid
Anyone whose seen dirty brake fluid knows when it’s dirty. Black brake fluid sticks out like a sore thumb when you see it. But not everyone has the time or the know how to check the color of their brake fluid.
So, pay attention to feel of your brake pedal when you brake. A brake system working on dirty fluid won’t work properly. The pedal will start to feel soft or spongy, and you’ll have to hit the brakes multiple times when you need a sudden stop.
What Do You Do If You See Dark Brake Fluid?
Regular brake inspections by yourself or by a mechanic can go a long way in preventing you from ever having to deal with dark brake fluid. Standard brake service by a mechanic (where your brake pads are replaced, and rotors are adjusted) includes replacing your brake fluid.
But you don’t have to wait for a mechanic to take care of the issue of black brake fluid.
Use a baster (preferably a temporary one that you don’t use with the new brake fluid) to get the old fluid out of your reservoir. Then, pour in some of the new brake fluid. Drive around for week, then pour some more of the new brake fluid in. This is called a fluid swap.
Repeat this process until you have the clear yellow color that effective brake fluid sports. Or you could just schedule an appointment with your mechanic at your earliest convenience. They will be able to perform a full brake fluid flush (replacing the old with the new in one visit).
Having dark brake fluid won’t cause long term damage right away. But take care of the issue as soon as you can.
What Are the Different Types of Brake Fluid?
Once you’ve determined you need new brake fluid, you need to figure out what type of brake fluid you need.
There are three main types of brake fluid:
DOT 3 is standard brake fluid, and most cars are compatible with DOT 3.
Brake fluids receive their classification based on the boiling point for the fluid. The boiling point is when the brake fluid begins to vaporize (which causes all the problems we mentioned earlier with dark brake fluid and “spongey brakes”)
The standard brake fluid has an average boiling point of 401 degrees Fahrenheit in warm conditions and 284 degrees for wet conditions.
DOT 4 is built for heavy-duty performance with a higher boiling point (446 degrees Fahrenheit for dry conditions and 311 degrees for wet conditions).
Functions like driving uphill, hauling heavy materials, and sudden drops in speed increases the temperature in your brake system. The added borate ester inside DOT 4 brake fluids give it a higher boiling point and make it more resistant to heavy pressure.
It is very important to never mix DOT 3 and DOT 4 brake fluids when performing a swap. And while most cars are built to be compatible with both, double check your owner’s manual to make sure your car is compatible with DOT 4 before you use it.
DOT 5 brake fluid is a silicone-based liquid used to maintain antique cars and in military equipment.
Though DOT 5 normally has the highest boiling point (over 500 degrees Fahrenheit in dry conditions), it’s not uncommon to find DOT 4 with a higher boiling point.
DOT 5 is resistant to water, so vehicles built to handle water are often DOT 5 compatible. But DOT 5 is seldom needed for standard use. And many cars built for normal wear and tear of the road are often not compatible with DOT 5 brake fluid. Also, never mix DOT 5 with either DOT 3 or DOT 4 brake fluid.
Most drivers never even consider the impact proper brake fluid has on your car. But you’ll learn if you ever must make a sudden stop while sporting really dark brake fluid.
So, pay attention to your brake pedal, keep a regular eye on the color of your brake fluid, and listen the next time your mechanic shows you that dark brake fluid so you can take action.