Refilling Brake Fluid Reservoirs: Process, Needed Tools & More
Brake fluid is a hydraulic fluid used in vehicle brake systems to transmit force into pressure. It serves several crucial functions:
- Transfers pressure from the brake pedal to the braking mechanism at each wheel
- Lubricates moving brake system components
- Protects against corrosion of brake lines and parts
Having the proper amount of high-quality brake fluid is essential for safe braking and preventing brake failure. Over time, brake fluid can become contaminated with moisture and lose effectiveness. Checking fluid levels and replacing old fluid is part of routine vehicle maintenance.
When to Refill Brake Fluid
Brake fluid serves a crucial purpose in your vehicle’s brake system and needs to be maintained at the proper level for safe braking. Most manufacturers recommend flushing and replacing your brake fluid every 2-3 years or 24,000-36,000 miles as brake fluid absorbs moisture over time. This absorbed moisture leads to a lower boiling point and degraded braking performance (Source).
Pay attention to symptoms of low brake fluid, as this indicates a leak or problem in the brake system. Signs include a brake pedal that feels soft or spongy, the brake pedal needing to be pressed farther to stop, longer stopping distances, and the brake warning light illuminating on the dashboard. Any of these symptoms mean you should check the brake fluid reservoir immediately. The fluid level may be low and need topping off if there is a minor leak. However, significantly low fluid levels or the need for frequent refills likely indicate a brake system problem needing professional diagnosis and repair.
Dangers of Low Brake Fluid
Having insufficient brake fluid can be extremely dangerous, as it impairs your vehicle’s ability to stop and can cause damage to brake components. When the brake fluid level is low, air bubbles can get trapped in the hydraulic system, causing a “spongy” brake pedal feel. This means you will have to press the pedal much farther to get the same stopping power, lengthening braking distance. In extreme cases with very low fluid, the brakes may fail completely.
Low brake fluid also allows water absorption and corrosion of internal brake parts like calipers, wheel cylinders, and metal lines. Over time, this can lead to complete brake failure due to leaked fluid or damaged components. Moisture-contaminated fluid causes pitting and erosion in steel parts as well as swelling and cracking in rubber components. All of this gradual damage from low fluid will make your brakes perform worse and worse.1
In summary, insufficient brake fluid compromises your ability to stop safely and damages the brake system through corrosion. Allowing the brake fluid reservoir to run dry is extremely hazardous and should be addressed immediately.
Checking the Brake Fluid
The brake fluid reservoir is typically located under the hood, mounted to the firewall at the rear of the engine compartment. It will be positioned in front of where the brake master cylinder is located [1]. On most vehicles, the reservoir is translucent so you can visually inspect the brake fluid level. If not, it should be marked with “Max” and “Min” lines.
To check the level, start by parking your vehicle on a level surface and turning off the engine. Pop the hood and locate the brake fluid reservoir. The level should be somewhere between the “Max” and “Min” lines – if it’s below the “Min” mark, it’s time to add more brake fluid. The level drops over time as the brake pads wear down and fluid flows into the calipers. You should check the fluid regularly as part of routine maintenance.
Tools Needed
Refilling your brake fluid reservoirs requires just a few basic tools:
- Funnel – You’ll need a funnel specifically designed for refilling brake fluid. This allows you to carefully pour fluid into the reservoir without spilling.[1][2]
- Brake fluid – Use fresh, new brake fluid that meets manufacturer specifications for your vehicle. Avoid fluid that has been sitting open or previously used.[3]
- Rags – Have rags on hand to wipe up any spills.
- Gloves – Wear gloves to protect your hands from brake fluid, which can be caustic.
Having the right tools makes refilling your brake fluid reservoirs a quick and easy process. Invest in a quality bleeder funnel kit specifically designed for the task.
Selecting the Right Fluid
When refilling your brake fluid, it’s important to select the right type specified by your vehicle manufacturer. The two main options are DOT 3 and DOT 4 brake fluid. DOT 3 fluid has a lower boiling point while DOT 4 has a higher boiling point and can withstand greater heat before boiling.
Most newer vehicles use DOT 4, while some older models use DOT 3. Check your owner’s manual to verify which DOT grade your vehicle needs. Using the wrong fluid can reduce braking performance.
The other key difference is between glycol-based and silicone-based fluids. Glycol fluids like DOT 3 and DOT 4 are more common. Silicone fluid is less common but handles heat better. However, you shouldn’t mix glycol and silicone fluid types. Stick with what your vehicle manufacturer recommends.
When selecting brake fluid, avoid cheap low-quality fluids that may boil faster. Trusted brands like Prestone and Castrol offer solid options. Your best choice is the brake fluid grade and type explicitly recommended in your owner’s manual.
Refilling Process
The refilling process involves cleaning the reservoir, adding fluid incrementally, and bleeding the brakes.
According to WikiHow, you should start by wiping the reservoir and cap clean with a dry rag to remove any dirt or debris. Make sure the reservoir is completely dry before adding new fluid.
Fluid should be added slowly and incrementally, according to Scotts Auto. Add a small amount, then check the fluid level. Continue adding fluid in small amounts, rechecking the level frequently, until full. Adding too much fluid too quickly can cause overflow.
The final step is bleeding the brakes to remove any air bubbles introduced during the refill process. Bleeding the brakes will ensure proper brake system operation. This involves opening the bleeder valves at each wheel cylinder one at a time while having someone press the brake pedal repeatedly.
Precautions
When refilling brake fluid, it’s important to take precautions to avoid issues down the line. Here are some key precautions to keep in mind:
Avoid spills and contact with painted surfaces. Brake fluid can be highly corrosive to paint, so any spills should be cleaned up immediately with water. Be careful when removing the reservoir cap and pouring in fluid.Source
Don’t mix brake fluid types. Each type of brake fluid has different properties. Mixing DOT 3 and DOT 4 fluid can cause damage to brake system components. Use the same type of fluid that is currently in your brake system.Source
Wear protective gloves and eyewear. Brake fluid can irritate skin and eyes. Proper gloves and eyewear should be worn to prevent exposure.Source
Dispose of used brake fluid properly. Don’t pour it down the drain. Check local regulations for proper disposal methods.
Working with brake fluid requires care, but taking basic precautions will allow you to refill your brake fluid safely.
Signs of Leaks
Two common signs that indicate your brake fluid may be leaking include:
Wet spots under the car – One of the most obvious signs of a brake fluid leak is spotting puddles or wet areas underneath your vehicle, typically near the wheels or brake components. Brake fluid leaks tend to leave behind light yellow to brownish colored wet spots on the ground. The fluid itself is slippery when touched.
Low brake fluid warning light – Most modern vehicles have a brake fluid level sensor that will trigger a warning light on the dash if levels get too low. This sensor light indicates it’s time to inspect the brake fluid reservoirs under the hood to confirm fluid is low. Topping off the reservoirs may temporarily remedy the light, but a warning light often means an underlying leak requires repair.
When to Seek Professional Help
In most cases, DIY brake fluid refills are perfectly safe. However, there are some situations where it’s best to have a professional mechanic handle the job:
If you have a large brake fluid leak that quickly depletes the reservoir, take your vehicle to a repair shop immediately. Large leaks indicate a possible problem with the brake lines, master cylinder, calipers, or wheel cylinders that needs professional diagnosis and repair according to Wagner Brakes. Driving with a major brake fluid leak can be extremely dangerous.
If you have refilled the brake fluid reservoir to the proper level, but are still experiencing brake problems like a “mushy” brake pedal, bring your car to a certified mechanic. Persistent issues after refilling the fluid may be caused by air trapped in the brake lines or a problem with the brake components that needs professional service according to Firestone Complete Auto Care. Don’t try to just keep refilling the reservoir without addressing the underlying cause.