Does Brake Fluid Evaporate? Essential Information

People often wonder if brake fluid can disappear over time. And the answer is yes, brake fluid can evaporate over time. First, let’s discuss the basics before exploring details.

Key Takeaways:

  • Brake fluid can evaporate over time due to moisture absorption, high temperatures, age, leaks, and improper storage.
  • Evaporated brake fluid should be replaced promptly to avoid a loss of braking performance.
  • Regular maintenance of the braking system is crucial to ensure optimal performance and prevent accidents.
  • Signs that brake fluid needs to be replaced include a soft brake pedal, reduced braking performance, brake fade, burning smell, and low brake fluid warning light.
  • Brake fluid should be stored properly in a sealed container designed for brake fluid and away from direct sunlight and heat sources.
  • Brake fluid should be checked for expiration before use.

What is Brake Fluid?

Brake fluid is a crucial liquid that assists the brake pedal in pressing brake pads onto rotors, ensuring the brake pedal functions properly. Brake fluid has different types, like DOT 3, DOT 4, DOT 5, and DOT 5.1. Each type of fluid is made for different purposes and has its own special traits.

For example, DOT 3 and DOT 4 are glycol-based and are commonly used in most passenger vehicles. DOT 5, on the other hand, is made from silicone and is usually used in military and fast cars.

Can Brake Fluid Evaporate?

Yes, brake fluid can evaporate over time. Brake fluid absorbs water from the air because it’s hygroscopic. As brake fluid absorbs moisture, it becomes contaminated and less effective at transferring force from the brake pedal to the brake calipers.

When brake fluid absorbs moisture, it also lowers the boiling point of the fluid. As the brake fluid becomes contaminated and its boiling point lowers, it becomes more prone to evaporating.

What Causes Brake Fluid to Evaporate?

Numerous factors contribute to brake fluid evaporation, such as:

  1. High temperatures: Elevated temperatures can cause brake fluid to evaporate more rapidly. The heat causes the water content in the brake fluid to transform into gas, leading to a decrease in fluid levels and diminished brake performance.
  2. Age: Brake fluid’s shelf life is limited, causing it to degrade and lose effectiveness over time. Aged fluid is more prone to evaporation, especially when it absorbs moisture, lowering its boiling point and heat resistance.
  3. Leaks in the braking system: Rapid brake fluid loss occurs when fluid escapes and evaporates due to leaks in the system. Regular inspections can help detect and address any potential leaks before they become significant issues.
  4. Improper storage: The rate of brake fluid evaporation can be accelerated if it is not stored correctly. Factors such as improperly sealed containers, exposure to extreme temperatures, or damp environments can lead to faster evaporation. To extend brake fluid’s shelf life, store it in a cool, dry place and securely seal the container.

Can Evaporated Brake Fluid be Replaced?

Yes, when brake fluid levels become low due to evaporation or other reasons, it is crucial to refill or replace the fluid promptly. To replace evaporated brake fluid, you should first remove the old fluid from the reservoir before adding new fluid. Using the right brake fluid specified for your vehicle is crucial, as the wrong fluid can cause brake malfunction or damage.

In addition to replacing the evaporated brake fluid, it is crucial to inspect the braking system for any potential leaks. If leaks are detected, they must be repaired before refilling the system with new fluid. This will ensure the longevity of your braking system and help maintain its optimal performance.

The Importance of Regular Brake Fluid Maintenance

Consistently maintaining your vehicle’s brakes is crucial because brake fluid can degrade, get contaminated, or decrease over time.

This necessitates frequently monitoring both the fluid’s level and quality, as well as adhering to the recommended replacement intervals specified in your vehicle’s owner’s manual.

Consistent brake fluid maintenance ensures that your brakes continue to perform at their peak efficiency, which in turn can help avert expensive repairs and reduce the risk of accidents.

When the brake fluid is in optimal condition, it guarantees that the braking system functions smoothly and effectively, making it a vital aspect of vehicle safety.

Signs That Your Brake Fluid Needs to be Replaced

Key Warning Signs That Your Brake Fluid Requires Replacement:

  1. A spongy or soft brake pedal: If your brake pedal feels spongy or soft when pressed, it could be a sign that air or moisture has entered the braking system, compromising the fluid’s effectiveness.
  2. Reduced braking performance: If your vehicle needs more distance to stop completely or requires increased brake pedal pressure to slow down, it could indicate a need for brake fluid replacement.
  3. Brake fade: Brake fade occurs when your brakes become less effective or completely unresponsive during continuous use, such as when driving down a long, steep hill. This could signal an issue with the brake fluid.
  4. A burning smell when braking: A burning or acrid odor while braking could indicate overheating in your braking system, which may be a result of degraded or contaminated brake fluid (also read: What Does Brake Fluid Smell Like?).
  5. A dashboard warning light for low brake fluid: Your vehicle’s dashboard warning light for low brake fluid can alert you to a potential issue with your brake fluid levels. It’s important to address this promptly to prevent further damage to your braking system.

If you notice any of these warning signs, promptly consult a qualified mechanic for a vehicle inspection.

How to Properly Store Brake Fluid

To make brake fluid last long and not evaporate too fast, store it correctly. Put brake fluid in a cool, dry place, far from the sun and heat. You also need a closed container made for brake fluid.

Never put brake fluid in an open container because water can get in and mix with the fluid. Also, check the expiration date because brake fluid can’t be used after a certain time.

Brake fluid has a limited shelf life, and it can lose its effectiveness after a certain period. If the fluid is expired, take it to a proper disposal place and replace it with fresh fluid.


To conclude, brake fluid can evaporate, particularly when it absorbs moisture and has a lower boiling point. High temperatures, age, leaks, and improper storage can all contribute to brake fluid evaporation, which can lead to reduced braking performance and safety hazards.

Therefore, it is essential for car owners to perform regular maintenance on their vehicle’s braking system and promptly replace evaporated brake fluid with the appropriate type. Proper storage of brake fluid is also crucial to prevent premature evaporation.

By following these guidelines, car owners can help ensure their brakes are working effectively and prevent costly repairs and accidents.

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