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Low On Brake Fluid Light On? Should You Be Worried

Brake Fluid Change Cost

Is your low brake fluid light on? Yes, your brakes are very important especially in automobiles since they are considered to be the primary safety features. If you are low on brake fluid you should be worried because a lack of fluid can affect your vehicle’s stopping power.

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Modern-day vehicles are equipped with advanced rear and front sensors for automatic braking and equal electronic brake force distribution. However, it’s important to understand the basic operation of the braking system so you can understand how important brake fluid is. 


Ok So What Is Brake Fluid? 

Brake fluid is a type of hydraulic brake fluid used in hydraulic braking systems. Brake fluid transfers force into pressure to aid in the movement of the brake pedal to actuate the pads and then the wheels. It helps provide the force needed to bring the vehicle to a complete stop. Brake fluid also serves as a lubricant. Since braking components are mostly made from metal components the fluid ensures that the parts are well-lubricated and don’t get corroded.


Vehicle owners may keep up with changing the rotors, pads, and drums especially when they notice decreased stopping power. Drivers tend to forget about replacing the brake fluid. An auto maintenance survey revealed that brake fluid is one of the most neglected components in a vehicle. 


What Happens When The Low Brake Fluid Light Comes On?

If the Brake Warning Light or the Low Brake Fluid light flashes on the dashboard this is a major sign that your brake fluid levels have dropped or it’s time you changed the fluid. 


How do your brakes feel? Are they a bit spongy? Do they go all the way down when you put your foot on the pedal? When the low brake fluid light comes on it’s accompanied by a wide range of symptoms such as:


The brakes are soft or have a mushy feeling

Every driver knows that the brake pedal offers a certain level of resistance when you press your foot down on it. As the fluid level decreases you’ll notice that the pedal becomes softer and softer. This is the most obvious sign of low brake fluid. 


Decreased Stopping Power

A soft pedal means decreased stopping power. When the brake fluid is low you'll have to press all the way down on the pedal to stop the vehicle. 


Brakes are making noises

If you don’t have enough brake fluid in your vehicle your brakes will start to make noises. You may hear a squeaking or grinding noise. 


How Long Does Brake Fluid Last?

The brake fluid in your vehicle lives in a sealed system which means it can last for several years. The intervals for changing the brake fluid can significantly vary depending on the auto manufacturer. Chevrolet suggests that owners replace the brake fluid in Chevy vehicles every 45,000 miles while Honda says to swap out brake fluid every three years regardless of the number of miles in the vehicle. Volkswagen also suggests owners replace the fluid every three years. 


On the other hand, luxury automakers like Mercedes Benz recommend that owners change the brake fluid every 20,000 miles or two years. Toyota, Ford, and Hyundai don’t provide any measures for replacing the brake fluid in their vehicles. 


The best way to determine whether it’s time to change the brake fluid in your vehicle is by checking the reservoir located on top of the master cylinder underneath the hood. 


Low Brake Fluid Can Stem From Contamination

Brake fluid isn’t really any different from any other fluids in your vehicle. Over time it can become contaminated which leads to low brake fluid. Brake fluid can be contaminated by deteriorating hoses and lines. The most common types of brake fluid contamination are:



Air contamination can occur in a variety of ways. Worn seals and components are one of the top ways air starts filtrating the braking system. As the pistons move back and forth it wears down the seals and they become less effective at sealing off the braking system. Replacing the worn seals and components air can also move into the system. Poorly bled brakes can also lead to a buildup of air in the braking system. 



Brake fluid is specially formulated to absorb moisture. Otherwise, water molecules would rot the brake’s internal components and completely damage the entire system. As brake fluid continues to absorb moisture it decreases the effectiveness of the brake fluid or minimizes its performance. The high temperatures during braking eventually make the fluid compressible giving that spongy feeling.


In addition, not all brake fluids are capable of absorbing moisture. Silicon brake fluid will only absorb so much moisture before it begins settling in the crevices and the low spots of the braking system. A build-up of moisture will eventually result in corrosion and damage to

braking components. In more modern vehicles moisture in brake fluid isn’t a major issue because these brake hoses and pads are made from flexible materials. 


Whether it’s moisture, air, or another foreign material once the brake fluid becomes contaminated it will need to be changed as soon as possible. 


Understanding Brake Corrosion

Corrosion is a phenomenon that ultimately affects all materials, especially on metal surfaces. When braking components start to rust or corrode it transforms the surface of the material and eventually works its way under the surface. The materials start flaking off which can lead to the line bursting and the pedal sinking right to the floor. It’s important to note that brake fluid itself doesn’t corrode but when the additives in the brake fluid are depleted or fully broken down the fluid doesn’t have any anticorrosive inhibitors.


What Are Brake Fluid Additives?

Brake fluid on the market contains additive packages which are formulated with a combination of anti-corrosion inhibitors, viscosity stabilizers, anti-foaming additives, and pH-balanced additives. These additives don’t last forever and when they break down over time the brake fluid will need to be replaced. 


Additives in brake fluid break down from:


  • The heat generated during braking activity
  • Cheap brake fluids which typically contain low-quality additive packages that break down faster than their counterparts
  • Thermal cycling is a result of the extreme heat generated while driving
  • Regular stop and go driving activity 


Why Is Your Brake Fluid Low?

When your brake fluid is low this can indicate a problem within your braking system. The common causes of low brake fluid are:


  1. Brake Line Leak

Brake fluid leaks are hazardous and put the life of the driver and other motorists on the road in danger. The brake lines are in charge of moving the braking fluid throughout the system. The lines are subject to high pressure while in operation, this causes damage to the brake lines and leads to the leakage of volumes of fluid. Oftentimes it starts with a small crack that develops and increases in size in time. Brake line cracks can cause large volumes of brake fluid to leak. 


Loose Bleeder Bolts

Bleeder bolts or valves help control the flow of brake fluid as it flows throughout the brake calipers. Like most automotive components, the bleeder bolts endure lots of wear and tear. If the brakes were recently repaired the bolts may have not been reapplied correctly. A situation like this can be easily remedied by tightening the bolts and adding more brake fluid. 


Worn Brake Pads

Brake pads provide the stopping power needed to bring a vehicle to a halt. However, brake pads wear and lose some of their stopping force. When the brake pads are worn this can lead to brake fluid loss. Driving with worn brake pads and low brake fluid can be dangerous.


Faulty ABS

The anti-lock brakes prevent the brakes from locking. Although the ABS units aren't always in operation they wear down over time which can trigger brake leaks.


How To Add Brake Fluid 

      Checking and adding more brake fluid to your vehicle should be a part of our maintenance plan. Brake fluid isn’t as vulnerable as motor oil so it doesn't need to be changed or filled as often. Checking your brake fluid can help you spot any contamination and if it’s continually running low chances are there is a leak somewhere within the braking system. 


To add brake fluid to your car you’ll need to locate the brake fluid reservoir which is under the hood in most vehicles. Typically, the brake fluid canister is located on the rear engine compartment on the driver’s side. Newer cars use translucent plastic with a fill line while some old vehicles are equipped with a metal reservoir with a clamp securing it in place. Make sure you consult the owner’s manual when it comes to opening the brake fluid reservoir because you risk contaminating it. Every auto manufacturer has different rules when it comes to contamination.


Using The Correct Type of Brake Fluid

Every car uses a different type of brake fluid. When you're adding brake fluid to the reservoir you’ll want to make sure you’re using the correct type of brake fluid. You can’t mix and match formulas or overfill the reservoir or you run the risk of causing a problem within the braking system. Brake fluid is very toxic and corrosive so you’ll need to exercise caution when you're replacing or adding more brake fluid. 


Most vehicles use either DOT3 or DOT4 brake fluid. If you’re not sure exactly which brake fluid is right for your vehicle make sure you check the owner’s manual. Once the brake fluid is changed the brakes will need to be properly bled. 


Common Brake Fluid Myths

Myth # 1 Moisture is the main problem with old brake fluid

In older vehicles, moisture is one of the top problems that drivers often face with the brake fluid. Yet, manufacturing techniques have greatly evolved and most braking systems use flexible materials that are resistant to moisture. Today a breakdown of the additives in brake fluid is more common. 


Myth #2 You don’t have to change the brake fluid

 The brake fluid does need to be changed. When the copper content exceeds 200 PPM the brake fluid will need to be replaced. New brake fluid with its additive package will be added so that protection is renewed. 


Myth #3 ABS systems don’t perform well after a brake fluid exchange

In some cars, the ABS might now allow the free flow of the brake fluid through the hydraulic control assembly. In a situation like this, the technician will have to actuate the HCU valves. 


The Bottom Line

It’s dangerous to drive a vehicle with low brake fluid. If your brake warning light, ABS light, or the low brake fluid light is on in the dashboard it’s important to have your vehicle serviced immediately. In most cases, low brake fluid is triggered by a serious problem within the braking system. Keep in mind that the brakes are the most important component of your vehicle. Therefore, having your brakes and the brake fluid regularly serviced is the responsible thing to do. It ensures the safety of your, your passengers, and others on the road. 


Common Questions

Q: Can you just add brake fluid to your car?

If your brake fluid is below the MIN line you should carefully screw off the brake fluid reservoir and add brake fluid until the line is near the MAX line. However, if it’s at or above the MIN line then your brake fluid levels are fine.


Q: Do you pump the brakes after adding brake fluid?

After intervals of pumping the brake, it's a good idea to top off the reservoir. When changing the brake fluid the fluid should look new in the bleeder hose. 


Q: When should you refill the brake fluid?

Maintaining the proper level of brake fluid is essential for your safety and the health of the vehicle. As a general rule of thumb, the brake fluid should be replaced every two to three years. 


Q: Can you mix old and new fluid?

Brake fluid is prone to moisture which is why it needs to be replaced. You cannot mix old and new brake fluid.

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