Does Brake Fluid Really Go Bad?

Does brake fluid really go bad? Unfortunately, the answer is yes, and when you use bad brake fluid in your car, you won't be able to get the optimal braking results, which can compromise your safety.

The thing is, you can't tell if brake fluid has gone bad by simply looking at it. Your car probably has a transparent brake fluid reservoir so you can see if it's at the proper level. That, however, doesn't tell you if your brake fluid is still usable.

How does brake fluid go bad?

On its own, brake fluid can survive for years, but the conditions it's subjected to while inside the reservoir, such as temperature changes and condensation, can cause moisture to get into the hoses and other parts of the brake system in a variety of ways.

Brake fluid is a hygroscopic type of fluid, meaning it absorbs water. And when this happens, the fluid's boiling point is lowered, so stopping ability is affected as heat in the system increases.

In times of heavy stress, such as stop-and-go traffic, off-road driving, or towing, your brake fluid can reach extreme temperature levels that impair your brake system’s stopping ability. At times, braking power can completely disappear.

So how long does brake fluid actually last?

Inside a sealed system, brake fluid's optimal usability can last up to two years. But as mentioned, its lifespan can be drastically shortened depending on your operating conditions. If you live in a high humidity area, such as near the beach, or if you are a racer by profession (or by passion), you will need to replace your fluid more frequently than every two years, or you will need to buy one that has a very high boiling point, such as DOT 4 brake fluids used by race car drivers.

How can you tell if your brake fluid has gone bad?

The most obvious sign that your brake fluid has already absorbed too much moisture is when your brake pedal has more travel than normal. That said, this is also a symptom of low brake fluid, worn brake pads, or air in your brake lines. Due to multiple possible causes, your best recourse is to have a trained mechanic diagnose your brake issue. A seasoned mechanic will usually be able to tell if your brake fluid needs replacing.