Having properly functioning brakes is crucial for safe driving. Your brakes rely on brake fluid to transfer force when you press the brake pedal to slow or stop your vehicle. This vital fluid plays a key role, so it’s important to maintain it properly and know the signs of any potential issues.
What is brake fluid?
Brake fluid is a hydraulic fluid that flows through the brake system when you apply the brakes. It transfers pressure from the master cylinder to the brake calipers, forcing the brake pads against the rotors to slow or stop your vehicle. Brake fluid has a few important functions:
- Transfers pressure through the hydraulic brake system
- Lubricates internal brake components
- Prevents corrosion in the brake system
- Withstands high temperatures
Common types of brake fluid include DOT 3, DOT 4, and DOT 5.1. These fluids have different dry and wet boiling points, meaning they are designed to withstand different levels of heat before vaporizing. DOT 3 and DOT 4 are glycol-based fluids, while DOT 5.1 is silicone-based. Always check your owner’s manual for the specific type of brake fluid recommended for your vehicle.
What causes brown brake fluid?
Over time and through normal use, brake fluid can start to take on a brownish color. There are a few common causes of this discoloration:
- Age: Brake fluid can oxidize and darken with age as the fluid absorbs small amounts of water over time. DOT 3 and DOT 4 fluids have a recommended change interval of every 2 years.
- Overheating: Excessive heat from hard brake usage can boil the fluid and turn it brown. The brown color comes from deposits left behind.
- Leaks: If the brake system develops a leak, it might allow contaminants into the fluid that can discolor it.
- Corrosion: Rust, dirt, or corrosion inside the brake system can also contaminate the fluid and give it a brownish tint.
Is brown brake fluid dangerous?
Brown or discolored brake fluid itself is not necessarily dangerous. However, it often indicates issues that do need to be addressed:
- Brown fluid means the fluid has absorbed water, which lowers its boiling point and increases the chance of brake fade or failure from fluid overheating and vaporizing.
- It can indicate there is a leak somewhere in the system allowing contaminants in.
- Particles from corrosion or deposits in the brake system are likely contaminating the fluid.
- Oxidation from age degrades the fluid and reduces its effectiveness.
So while discolored fluid alone may not make your brakes unsafe, it often goes hand-in-hand with moisture contamination and the presence of particles that can damage brake components. It’s a sign maintenance is required.
When to change brown brake fluid
Here are some general guidelines for when to change brown or discolored brake fluid:
- Change fluid that is darker than a light amber color.
- Drain and replace fluid if it is beyond the recommended change interval (typically every 2 years).
- Change fluid immediately if you have symptoms of a brake system problem like soft pedal, loss of braking power, or grinding noises.
- Replace fluid that has been exposed to air due to leaks or brake work.
- Fluid that has turned sludgy or polluted looking should be changed right away.
You may also want to flush the entire brake system to remove any contaminants that could be present anywhere in the hydraulic lines, master cylinder, ABS unit, or brake calipers. Follow your vehicle repair manual for proper brake system flushing procedures.
Steps for changing brake fluid
Here is a summary of the general process for draining old brake fluid and refilling with fresh fluid:
- Lift the vehicle and support it safely on jack stands.
- Locate the bleeder valve on each brake caliper and use a box end wrench to open the valve.
- Attach a clear plastic hose to the bleeder and submerge the other end in a container to catch old fluid.
- Pump the brake pedal a few times until fresh fluid emerges from the hose.
- Close the bleeder valve and move to the next wheel.
- Repeat steps for each wheel until all calipers have been drained.
- Refill the master cylinder reservoir with fresh, clean brake fluid.
- Bleed the brakes starting with the wheel furthest from the master cylinder.
Bleeding the brakes is crucial to purge any remaining air bubbles and contaminants from the system. Consult your vehicle repair manual for the proper brake bleeding procedure. You may need a brake bleeding tool for one-person bleeding if you don’t have an assistant.
Preventing brake fluid deterioration
Here are some tips to help maintain fresh, clean brake fluid and avoid deterioration:
- Change fluid on schedule every 2 years or as recommended
- Use only new, sealed containers of brake fluid
- Avoid exposing reservoir to moisture from rain or car washes
- Repair any leaks immediately to prevent contamination
- Inspect master cylinder reservoir regularly for fluid level and clarity
- Avoid hard brake usage which can boil fluid
- Drive smoothly to minimize heat buildup in brakes
By staying on top of scheduled brake maintenance, you can keep the system full of fresh fluid and help extend the life of all brake components.
Signs of brake problems
Be alert for any of these warning signs that may indicate issues in the brake system:
- Spongy brake pedal
- Reduced braking power
- Brake pedal goes to floor
- Grinding noises when braking
- Brakes pulling to one side
- Leaking fluid visible on ground
- Brake warning light illuminated
If you experience any problems with braking, get your vehicle checked right away for proper diagnosis and repair. Driving with any brake issue increases risk of accidents and failure.
Conclusion
While brown or discolored brake fluid alone does not necessarily mean the brakes are dangerous, it does indicate moisture absorption and possible contamination are degrading the fluid. Have the brake system inspected anytime the fluid is dark to address any underlying issues. With proper fluid changes and system maintenance, you can keep fresh fluid in the system and ensure safe, reliable braking performance.
Brake Fluid Change Intervals
Here is a table summarizing recommended brake fluid change intervals by manufacturer:
| Manufacturer | Recommended Interval |
|---|---|
| Toyota | Every 3 years |
| Honda | Every 3 years |
| Ford | Every 3 years |
| GM | Every 2 years |
| Chrysler | Every 2 years |
Most vehicle manufacturers recommend flushing the brake fluid at least every 2-3 years as general maintenance. Check your owner’s manual for the specific interval recommended for your make and model.
Brake Fluid Boiling Points
Here is a table showing the typical dry and wet boiling points for common brake fluid types:
| Fluid Type | Dry Boiling Point | Wet Boiling Point |
|---|---|---|
| DOT 3 | 401°F (205°C) | 284°F (140°C) |
| DOT 4 | 446°F (230°C) | 311°F (155°C) |
| DOT 5.1 | 500°F (260°C) | 356°F (180°C) |
Higher dry and wet boiling points indicate the fluid is more resistant to brake fade caused by overheating and vaporizing under hard use. Always use the specific fluid called for by the vehicle manufacturer.
In summary, brown or dirty brake fluid is a tell-tale sign moisture and contaminants are compromising the hydraulic system. While not necessarily an immediate danger, discolored fluid means it’s time to flush the system and replace it with fresh fluid to maintain optimal braking performance and safety.
