Is the low brake fluid light on again? If it’s one thing that your vehicle strongly depends on its proper functioning brakes because without them it won’t be driveable. Most car owners know that changing the motor oil is one of the most important maintenance services that shouldn’t be overlooked. But what about the brake fluid?
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Brake fluid is another crucial part of your vehicle’s operation. After all, most vehicles are equipped with hydraulic braking systems which rely on a reservoir of brake fluid to bring the car to a stop when the brakes are activated. Just like motor oil, eventually, brake fluid begins to break down and become less effective. What should you do?
What Is Brake Fluid and What Does It Do?
Brake fluid actuates critical components of your vehicle’s braking system to make sure you can bring it to a halt. It is a specialized type of hydraulic fluid that’s composed of glycol or silicone and it's available in a few different varieties.
This chemical solution is designed to amplify the force you put on your brakes when you tap the pedal with your foot. When you put your foot on the brake pedal the brake fluid turns into pressure. Depending on the vehicle this pressurized system electronically or mechanically pushes the pistons all the way through the master cylinder.
The brake fluid then applies pressure to the calipers, which activates the brake pads, which in turn clamps down on the rotors that are attached to the wheel hubs. This intense friction is what slows down the vehicle and brings it to a stop. Put simply, the brake fluid creates the high-pressure build-up required to reduce the speed of a car and bring it to a complete stop.
What Are The Different Types of Brake Fluid?
You might be surprised to learn that brake fluid isn’t a “one size fits all” type of product. There are three main types of brake fluid:
- DOT3
DOT3 brake fluid is the most common type of brake fluid. It’s categorized as a high-performance hydraulic brake fluid that’s generally used in a disc, drum, and anti-skid braking systems. This brake fluid can absorb water through the air and it has a boiling point of 401 degrees Fahrenheit. Brake fluid is subject to high temperatures which is why it must have high boiling point temperatures which measure how fast it vaporizes.
- DOT 4
This brake fluid has a boiling point of 446 degrees Fahrenheit. Its chemical composition greatly reduces its water absorption rate. This type of brake fluid is commonly used in European cars.
- DOT 5
Unlike DOT 3 and DOT4 this brake fluid is silicone-based and has a boiling point of 500 degrees Fahrenheit. DOT 5 only absorbs water when the air becomes trapped in and it’s not recommended for vehicles that are equipped with ABS.
What Does Low Brake Fluid Mean?
Now that you know a bit about how brake fluid works and what type of brake fluids are on the market it’s time to explore what it means when your car is low on brake fluid. The low brake fluid warning light on your car dashboard is the first sign of trouble.
Each car is different. On older cars, you might notice that the parking brake light is illuminated; this is also a low brake fluid warning. In some vehicles, a combination of lights might flash on such as the ABS and the parking brake light. When your car is low on brake fluid this indicates that the fluid reservoir is low and in some cases, it might be completely empty.
When the brake fluid levels are low, pressure in the braking system is significantly reduced which greatly reduces braking force.
Top Signs of Low Brake Fluid
Besides the dashboard warning light, you will be able to tell when your car’s brake fluid levels are low. The top symptoms of low brake fluid are:
Soft or Spongy Brake Pedals
Low brake fluid can cause that soft and spongy feeling in your brake pedals. While brake fluid is incompressible it begins to boil which occurs when you haven’t changed the brake fluid in ages or when it needs to be changed such as when moisture makes its way into the master cylinder. When the fluid starts to boil it creates bubbles that are made of air. Air is compressible.
Air in the brake lines makes the brake pedals incredibly soft and you’ll find yourself pushing down further on the pedal to bring your car to a stop. To fix this problem, you’ll need to have the brake fluid bleed from your braking system and replaced with fresh fluid.
Worn Brake Pads
Is it time to replace the brake pads on your car? If you hear a squealing or squeaking noise coming from your brakes chances are your brake pads have reached the end of their useful life. Worn out brake pads will cause the brake fluid to drop incredibly low. This is because when the brake pads are thin, the caliper piston has to travel further away from its housing to meet the pads.
This causes the brake fluid to work harder, increasing the boiling point because temperatures increase when the brakes have to exert more pressure. When you have the brake pads replaced you should make sure that the remaining brake fluid is fully flushed from the braking system. Whenever the hydraulic system is opened up and exposed to air the risk of contamination is high.
Discolored or Dirty Brake Fluid
If you notice that the brake fluid in the reservoir is any shade of brown or black, the fluid is old, dirty, and likely contaminated with other particles. When the brake fluid needs to be changed the low brake fluid light will be triggered on the dashboard.
Does Brake Fluid Just Run Out?
Under normal circumstances, brake fluid isn't consumed and doesn't just evaporate. However, brake fluids are hygroscopic which means that they absorb water from the humidity. No matter how tightly the brake reservoir is closed over time moisture will contaminate the brake fluid.
Water has a lower boiling point than brake fluid. The heat produced from the braking system will eventually bring the fluid and water to a boil causing the brake fluid to deplete at a faster rate.
Over time, you should expect to lose some brake fluid. If it drops low in a short timespan this can indicate a serious problem within your braking system such as a leak.
Low Brake Fluid Caused By A Leak
Unlike motor oil or transmission fluid, brake fluid doesn't have a distinct color or smell. If the leak is small enough you might not even see evidence of a leak underneath your car. Therefore, determining whether you have a brake fluid leak can be difficult. Damaged hoses, overworked critical braking components can all cause fluid leaks.
When brake fluid begins escaping the system it will seem as if the brake fluid reservoir is being drained. The most common reasons why your car is leaking brake fluid can be attributed to:
Damaged Brake Lines – If there is a hole or crack in the brake lines the fluid won't be able to reach its destination without seeping out.
Worn Seals – After a while, the intense heat generated during braking will wear out the seals in the calipers and other components within the braking system. When these essential parts begin to show signs of extensive wear it leads to brake leaks.
Master Cylinder Leak
Leaks in the master cylinder are common. The master cylinder is assembled with several valves and seals that will eventually wear out.
A minor leak will have you topping off the brake fluid reservoir from time to time to time. Small leaks could end up causing major problems in the long run. Worst case scenario the leak can flow to the brake pads creating a very dangerous situation. Long-term leaks will result in the brake pads wearing out faster than they normally would.
Loose Bleeder Valve
Both the brake caliper and drum are designed with a bleeder valve. A loose or damaged bleeder valve can lead to a big brake fluid leak and air to be expelled from the brake lines.
Damaged ABS Module
The ABS braking system also contains a high amount of pressure from the brake fluid. The seals around the brake fluid reservoir become corroded, worn, or damaged
The cost of repairing a brake fluid leak mainly depends on what part of your braking system has been damaged. If there is a problem with the intake lines it can cost between $100-$300. If the problem is within the master cylinder you could be paying up to $400 in repair costs.
Can You Drive WithThe Low Brake Fluid Light On?
Low brake fluid will have a direct impact on the brake pads and in some instances can cause vibrations when you step down on the brake pedal. While low brake fluid won't damage your brakes it will affect your stopping power. Driving a car with decreased brake fluid levels is dangerous. At any moment you could lose the ability to stop your car which can lead to a serious accident and you can harm other motorists. Driving with the low brake fluid light on is highly discouraged.
Low Brake Fluid Common Questions
Q: If the brake fluid level is low can I just add more?
When was the last time you had your brakes serviced? If it's been a long time since you added brake fluid to the reservoir simply refilling it may be enough to get the low brake fluid warning light to turn off. You should closely monitor the reservoir to make sure the fluid levels don't drop over the next couple of weeks because this can indicate a leak.
If the brake fluid is dirty or discolored it needs to be flushed from your braking system and then fresh brake fluid should be added.
Q: How do I check my brake fluid levels?
You can check your brake fluid levels by measuring how much fluid is left in the reservoir. The brake fluid reservoir is located under the hood on the master cylinder. Locate the maximum and minimum line on the exterior of the reservoir. If the fluid is at the minimum line then it's time to top up on the brake fluid. It won't hurt to have your brakes inspected by a professional.
Q: How long should brake fluid last?
How long brake fluid lasts in your car depends on the environment and the type of brake fluid. In high humidity areas moisture is absorbed through the seals and hoses. Nascar drivers change the braking fluid in their vehicles frequently due to significantly higher brake temperatures the vehicle is subject to.
For the average driver, brake fluid can last for about two years or a bit longer depending on your driving habits. You can make sure your brake fluid lasts long by being careful about how often it's exposed to the natural environment. Also, using brake fluid that is packaged with nitrogen will prevent moisture contamination.
Q: Can low brake oil cause the car to stall?
Whenever your vehicle is low on any fluid you automatically wonder if it can cause your vehicle to stall. In some cases, excessive air in the brake lines can cause a vehicle to stall out while braking.
Never Ignore Low Brake Fluid Issues
Are you having brake issues? If your low brake fluid light is flashing on regularly this can indicate a problem with your vehicle’s braking system. Over time, low brake fluid puts extra stress on the calipers and brake pads leading to serious leaks. Operating a vehicle without properly functioning brakes is a major safety hazard. It's a good idea to have your brakes regularly serviced by an experienced technician. Routine brake inspections can help you spot minor problems before they become bigger.