On two occasions during my tenure as a seasoned auto mechanic, I found myself behind the wheel of a client's vehicle when the braking system gave out. Such incidents remain etched in your memory forever. Fortunately, these vehicles had been brought into the workshop due to the owners experiencing a spongy brake pedal or sensing an unusual behavior while coming to a stop.
Next, I encountered a terrifying scenario while operating my vehicle. Suddenly, as I was reversing out of my driveway, the brake pedal sank all the way to the floor.
Fortunately, I wasn’t going very fast. I promptly pulled up the parking brake and managed to bring my SUV safely to a halt. The brake line, hidden within the frame, had corroded over time.
On all three occasions, I was remarkably lucky. Fortunately, there wasn’t any harm done, nor were anyone hurt. But then, why did these incidents occur? The reason is straightforward— brake fluid goes bad. Here’s what you need to know, with help from an expert — Ron Schornstein, president and CEO of Acustrip, which markets fluid testing products.
What Is Brake Fluid and What Does It Do?
Brake fluid is a solvent-based, hydraulic fluid. It contains synthetic additives formulated to withstand high pressures and temperatures when transferring force from the brake pedal to the brake pads or shoes.
A network of lines and hoses deliver the pressured brake fluid to the disc pads, forcing them to clamp down onto the disc rotor or drum brake shoes outward against the brake drums. This force creates tremendous friction that brings your car to a halt.
What Makes Brake Fluid Go Bad?
Unfortunately, the additives that protect brake fluid — lubricants, corrosion inhibitors, acid neutralizers and viscosity stabilizers — break down and wear out. Once they lose their effectiveness, brake fluid’s performance becomes significantly lower. This causes:
- Difficulty bringing your car safely to a stop;
- Brake fluid leaks;
- Brakes locking up;
- Grinding or squeaking noises when braking;
- An illuminated anti-lock braking system light.
Moisture absorption
Brake fluid is extremely hygroscopic, meaning it can absorb and hold moisture. Moisture in brake fluid also causes metal brake parts to rust and corrode from the inside out, and rubber parts to swell, deteriorate and weaken.
The heat friction that slows rotor and wheel rotation transfers to the brake fluid. This causes the moisture to boil, producing gas bubbles. Gas bubbles in brake fluid can compress, causing brake fade (the pedal feeling mushy) and greatly increasing stopping distances.
Incompatibility
Different types of brake fluids are not always compatible with each other.
- DOT 2 brake fluid is mineral based and should not be mixed with any other DOT rated fluid.
- DOT 3 and DOT 4 both use glycol ethers as their base. Mixing DOT 4 with DOT 3 brake fluid is acceptable; however, you should never introduce DOT 3 into DOT 4.
- DOT 5 brake fluid is silicone-based and should not be mixed with any other type of DOT brake fluid.
- DOT 5.1 is equivalent to DOT 4, yet boasts a significantly higher boiling point.
Refer to your owner’s manual or consult with an expert at an auto parts store to determine the appropriate type of brake fluid for your car.
The "DOT" abbreviation represents the U.S. Department of Transportation, which establishes the criteria for brake fluids, encompassing areas such as:
- Boiling points;
- Interactions between chemicals and other components utilized in brake systems;
- Chemical and temperature stability;
- The containers are properly labeled.
- Viscosity levels.
Chemical breakdown (additive depletion)
As a result of prolonged exposure to severe temperature changes and immense pressure, brake fluid additives tend to degrade over time. This degradation may render the brake fluid corrosive, leading to corrosion of metallic elements within the braking system as well as deterioration of plastic and rubber components in the brakes.
Contamination
Even though it’s a closed system, contaminants like debris may still find their way into the brake fluid hydraulic setup. A tiny vent in the master cylinder stops the issue of brake system vapor lock, an occurrence that could severely affect the efficiency of your brakes.
The vent enables airflow into the reservoir when the brake fluid level decreases due to pressing the brake pedal. When you release the pedal, this air exits. Moisture-laden air entering the master cylinder can cause issues. dust And dirt, all of which pollute the liquid.
Electrolysis
Here’s another lesser-known cause of brake fluid failure: when dissimilar metals come into contact or due to inadequate grounding, electrolysis can occur. This process leads to component degradation as an electrical current meant to go to ground travels instead through liquids such as rainwater, salty air, or road salts.
C clamps and other metal fittings used to secure brake lines to the vehicle’s frame or underside can deteriorate due to corrosion when exposed to environmental factors. This degradation of the clamps and hardware leads to damage of the brake lines over time.
Faulty grounding of components or bodies can lead to numerous issues such as damaged metal control cables, deteriorated heater cores, erratic behavior of lights and other electrical equipment, along with problems related to engine performance. Should all the brake lines and hoses on your automobile be out of sight, request your mechanic to check them each time you have your vehicle serviced.
Ways to Identify If Your Brake Fluid Has Gone Bad
Inspect the brake fluid for quality and condition. using test strips or a brake fluid pen tester Depending on the tester used, it can ascertain whether the fluid has contaminants present. pH (acidity) levels which can harm the braking mechanism.
Schornstein states that hidden contaminants in any vehicular fluids can rapidly lead to the early malfunction of not just that component but also others.
At What Point Should You Replace the Brake Fluid?
Every second year or 48,280 kilometers.
The brake fluid ought to appear as clear yellowish to light brown with a smooth, oily texture. Should the fluid be dark brown, contain black grit-like debris, or if the fill cap gasket seal feels soft and squishy, then it is definitely time for replacement. bleed and replace brake fluid and install a new master cylinder gasket/seal.
Check brake fluid Check the brake fluid level each month and inspect its condition every six months or after driving 6,000 miles. Monitoring these aspects yourself can help avoid expensive brake work and potential collisions, since this upkeep is simple enough for most people to handle at home.
About the Expert
Ron Schornstein serves as both the president and CEO of Acustrip In Denville, New Jersey, Acustrip manufactures various fluid testing products and devices for both the transportation sector and household use.
