Signs of Bad Brake Fluid

Brake fluid is a specially formulated fluid that transmits the pressure generated by the master cylinder to the calipers and/or wheel cylinders when the brake pedal is pressed.

Your vehicle’s braking system is responsible for slowing it down and stopping it. Your braking system is a hydraulic system. It transmits the pressure of your foot on the brake pedal to the brake discs or drums on each of your vehicle’s wheels. Friction material in each brake pushes against the spinning wheel, reducing its speed. The harder you press on the brake pedal, the faster you slow down or stop.

Brake fluid is a specially formulated, usually glycol-ether-based fluid. It is designed to maintain a constant viscosity, a low level of compressibility, a high boiling point, and a resistance to corrosion.

Your brake fluid fills the lines that connect the brake pedal with the brakes in your wheels. The brake fluid sends your brake foot’s commands to each brake. Your brake fluid also lubricates the moving parts of your braking system it touches and protects against corrosion. Any problems with your brake fluid can reduce the effectiveness of your braking system, creating a potential safety concern.

Your brake fluid reservoir is located under the hood. Instructions for checking your brake fluid, and topping it up when necessary, can be found in your owner’s manual. Use only the brake fluid type specified in the manual.

What are the signs of bad brake fluid?

There are several ways to tell that you may have bad brake fluid. Let’s see what they are:

• Dirty or discolored brake fluid: When you open your hood and check the brake fluid in the reservoir, you may notice that it is not clear, but is a tan, brown, or even black color. You might also notice dark particles suspended in a lighter-colored fluid. Either of these scenarios indicates that you have bad brake fluid, because it has become old and/or contaminated, making it less effective. Call a professional mechanic.

• Low brake fluid level: You may notice that your brake fluid level is low, either from a dashboard warning light or by checking the level in the reservoir. This could mean that there could be a brake fluid leak somewhere in your braking system, especially if you have recently topped it up. If you do not get this problem fixed, and enough of your brake fluid leaks out, you will have little or no braking power, and your car will not stop. The consequences could be disastrous – get your car to your mechanic’s repair shop immediately!

• Brake pedal feels soft or mushy and car is hard to stop: If your brake pedal has been feeling softer and softer over time when you apply it, this is a definite sign of bad brake fluid. Moisture that has built up in your brake fluid can boil under the heat and pressure of hard braking, creating air in the brake lines. Because air is compressible, unlike brake fluid, the pedal goes down farther, loses its firm feel, and reduces your car’s stopping ability. Time to get your brakes fixed.

• Your check engine or ABS warning light comes on: Many current cars have brake system sensors connected to the engine computer. A low brake fluid level can trigger a trouble code and illuminate the check engine light. Your anti-lock braking system’s computer may also let you know of drop in brake fluid level by turning on its warning light. Top up your fluid and have your car checked by your mechanic if any other symptoms of bad brake fluid are present.

Should you drive with bad brake fluid?

It is not safe to operate any vehicle with any braking problem. If there is any sign that the brakes are not performing as originally intended, the vehicle should immediately be placed out of service, and repaired. If you are simply having your brake fluid replaced as part of routine maintenance, with no symptoms noticed, the vehicle can safely be driven to a repair shop.

How do you fix bad brake fluid?

If your car’s brake fluid is old, discolored, or contaminated, it cannot be fixed; it must be replaced. And before it is replaced, the rest of your braking system should be checked, to make sure that there are no other brake problems that need to be fixed at the same time.

Bleeding vs. flushing your brakes

There are two different types of service procedures for bad brake fluid: bleeding and flushing. Many auto service shops, both dealers and independents, recommend a brake fluid flushing process as the best way to service your brake fluid. Let’s consider both and see which makes more sense for you and your braking system.

Bleeding your brakes: This involves manually pumping enough new brake fluid through your brake lines to eliminate any air that may be in your brake lines. The vehicle’s four brakes are bled individually, using a bleed screw found on each brake’s caliper or shoe. Bleeding should return proper pedal feel and performance to your braking system.

Flushing your brakes: This process goes a step beyond the bleeding procedure, replacing all of your old brake fluid with clean, fresh new fluid. This is often done with a powered flushing machine. After the old fluid is removed from the reservoir, the machine forces new brake fluid through your brake lines, and the remaining old fluid is drained out at the bleed screws located on each wheel’s brake. Flushing gives you 100% new brake fluid throughout your braking system.

Here are a few guidelines on whether bleeding your brakes is an adequate way to service them, or if you should have your braking system flushed:

• What does your vehicle manufacturer recommend? Check your owner’s manual or service booklet for the manufacturer’s suggestions on when and how to service your brakes. If there is no recommendation for flushing your brakes, it is usually not necessary, especially if you have followed the recommended service intervals and the fluid looks translucent or clear, not dark and murky.
• Are there any indications of a brake fluid problem? Have you noticed any of the symptoms of bad brake fluid listed above? If so, have your braking problem diagnosed by your mechanic and repaired right away, before you are unable to stop. If you have bad brake fluid, then a flush may be an appropriate step toward restoring the effectiveness of your brakes.

Can you replace brake fluid by yourself?

If you have good mechanic skills, along with a complete knowledge of hydraulically actuated braking systems, you can probably maintain and repair your car’s braking system. This is not a suitable project for the casual DIYer. Your car’s brakes are too important to your safety to have an amateur working on them. Leave this one to the professionals!

What you can do to keep yourself and others safe is to regularly check your brake fluid, keep it topped up with fresh fluid of the right type, and notify your mechanic immediately if you notice any of the signs of bad brake fluid that we have provided for you in this article. Drive safely!