How to Bleed Brakes by Yourself (6 Methods)
Mechanical vs Hydraulic Brakes
During the first quarter of the 20th century very few vehicles on the road used a hydraulic brake system. Most vehicles used a mechanical braking system actuated by rods and linkages not far removed from the stage coaches of the late 19th century. These systems were often troublesome to adjust and apply the brakes evenly and consistently. Adjustments in linkages and at the brakes themselves were frequent and inconvenient. Short of a trailered show car or museum piece these days, it is a scary proposition to head out in modern traffic in a Model T or other such ride with mechanical brakes.
Hydraulic brakes, often referred to as “juice brakes” by hot rod enthusiasts, came to be on GM cars in the early 1930s and Ford followed suit by the end of the decade. These hydraulic brakes systems used brake fluid, under pressure from the master cylinder and it’s connected brake pedal when employed by the driver, to apply the brakes. Between the low maintenance of the system and its overall braking effectiveness, hydraulic brakes took off and saw widespread use. The completely enclosed system uses high pressure tubing and reinforced hoses to transfer the fluid pressure coming from the master cylinder to each wheel’s brake, be it a disc brake caliper or a drum brake wheel cylinder. This fluid, under pressure when the brake pedal is applied, is the “life blood” of any hydraulic braking system and requires periodic maintenance as well as specific filling procedures referred to as brake bleeding.
What is Brake Bleeding?
Brake bleeding is the process of removing all air and contaminants or old brake fluid from the hydraulic system of your vehicle’s brakes. This process is essential for maintaining the optimal performance and safety of a vehicle's braking system. As the hydraulic braking system ages, the fluid becomes contaminated with debris and moisture and the only way to return the hydraulic system to its original state is to flush the system of contaminants using new fluid and proper brake bleeding procedures. Additionally, any time air is introduced into the system, either via a leak or the intentional opening of the system for repair or replacement of a hydraulic brake system component, this air must be removed via the brake bleeding process.
The process of bleeding brake systems can be accomplished in several ways (more on that later), but to summarize, the hydraulic brake system must be placed either under pressure or a vacuum to push or pull the old fluid and trapped air, respectively, from the system. This manual brake bleeding process uses one person to pump the brake pedal to build hydraulic brake system pressure and a second person to open and close the bleeder valves/screws at the drum brake wheel cylinder or disc brake caliper to allow old fluid and/or air to escape.
Bleeding brake systems in this manner is very common and requires the minimum of hand tools (usually just a wrench or socket for the bleeder screws and a fluid catch bottle) but it does require the help of a second party, something that may be tough to find at 10pm on a Wednesday night if that’s when you’re ready to bleed your new brake system. However, there are alternatives to this two-person process that are often quicker and more efficient that will allow you to bleed brakes on your own.
Is Bleeding Brakes Necessary?
Whether you’re performing maintenance or replacing a physical part of the hydraulic system on your vehicle’s brakes, any time the system is accessed the system should be bled of air and contaminates. The most common need will be when replacing a brake caliper or wheel cylinder during a brake rebuild, or replacing a leaking component, such as a brake hose or a section of rusted or damaged brake line. Whatever the reason, if the system is opened and brake fluid is allowed to escape there’s a good chance air has entered the system. The only way to remove this air (or flush a system of old fluid that has contaminates or moisture in it) is to bleed the brake system.
How much brake bleeding will be determined by the service action performed. If only replacing the left front brake hose, and don’t normally need to bleed the complete brake system unless you allow the complete system to drain. In this case, simply bleeding the left front brake circuit will often be all that is required. As for when one person should bleed brakes from an in service time standpoint, most agree that a full system flush of old brake fluid should be performed every two years. Brake fluid absorbs moisture, and this moisture can wreak havoc on your brake system. Flushing the system of old, dirty and moisture laden fluid is the best way to keep your brake system in top working order.
Will Brakes Bleed Themselves?
When you consider the fact that modern disc and drum brakes automatically adjust themselves for wear to maintain optimum braking function, it is easy to believe that brakes may indeed be self-bleeding in some shape or form. Unfortunately, that is not the case. Being a sealed hydraulic system, if any “self-bleeding” is going on you have what we call in layman’s terms, a leak! As such, to perform any brake bleeding operations there will need to be human/tool intervention on the hydraulic system. This may be as simple as a brake bleeder screw wrench or possibly more advanced with a pressure or reverse brake bleeder tool. We’ll explain these options in further detail below.
So, what happens when you don’t bleed your brakes? As mentioned above, brake fluid absorbs moisture, and this will cause brake systems to rust internally. The rust particle traveling through the braking system will often cause damage to seals (leaks internally and externally and plug up small fluid ports in proportioning valves and master cylinders. It is easy to prevent this by simply flushing your brake system on a regular basis, just as you would your cooling system.
Is Bleeding Brakes Easy?
Generally speaking, yes, brake bleeding is not a difficult task. In most cases for those with general mechanical knowledge and a few basic hand tools, bleeding brake lines can be accomplished in a home garage or shop with little effort. However, the more advanced the braking system, the more knowledge or research on the system will be required to bleed the hydraulic braking system safely and effectively. We are, after all, talking about a major safety system of your vehicle.
A basic disc/drum setup may easily be bled with a helper, and a few select hand tools, but more intricate systems with anti-lock braking modules, electric parking brakes, and more should be thoroughly researched to be able to correctly bleed the system without fear of causing damage to the hydraulic brake system hardware or prevent a complete elimination of air in the system. One word of caution when it comes to vehicles with GM-style proportioning valves. We highly recommend our proportioning valve bleeder tool to maintain the valve’s centered position when bleeding your brake system. Simply unscrew the brake pressure warning light switch, screw this tool into place, and then go on about bleeding your brake system.
Who Can Bleed My Brakes?
Thanks to varied right to repair laws, everyone has the right to repair their own vehicle. While most of these laws are aimed at modern technology laden vehicles that require scanners and special software to repair (making these items available to the public for purchase), it still means you have the right to perform repairs, maintenance, and more on your personally owned vehicles. You could of course have a professional mechanic, be it a shop you would have to tow/trailer your vehicle to, or a mobile mechanic scheduled to perform any repairs directly at your own personal garage or shop, there is cost incurred. This is especially true if you must have a vehicle towed. In the case of bleeding the brakes after any brake system service, we believe the cost of any brake bleeder tools and your own personal time is going to be far less than a shop’s labor charge and a tow bill. Obviously, at the end of the day you need to know your own mechanical repair abilities, but for most of us and the vehicles we are talking about, bleeding your own brakes is usually going to be the best answer.
Methods of Bleeding Brakes by Yourself
There are several ways one person can bleed brakes by yourself on a vehicle. While the basic two-person method commonly used is popular, we want to focus on how you can bleed brake fluid by yourself. We’ll review each process of having only one person to bleed brakes here and what you’ll need to get the job done correctly. These methods are all proven and used daily by commercial shops and mechanics, and you can use the very same methods at home in your garage to bleed brakes by yourself with just a small investment in tools and your time.
Option 1: Manual Brake Bleeding
Often, we’ve employed our better half to aid in the two person brake bleeding process. While this can, and has, worked in the past, you can indeed bleed brakes by yourself using several different methods. The most basic of these one person to bleed brakes options is to use a special one man brake bleeder hose that incorporates a spring loaded check valve that closes every time you release the brake pedal. Simply connect this hose to the appropriate bleeder screw, use a fluid catch bottle, and ensure you keep your master cylinder topped off with fresh brake fluid, and you’re good to go, just you and your project car. No arguments or waking your significant other at 2am just to help bleed the brakes!
Option 2: Vacuum Brake Bleeding
A great option for those looking to perform general brake bleeding operations on their own is by using a vacuum bleeding system. With vacuum bleeding the old fluid and air bubbles in the system are pulled through the lines via vacuum (either a hand pump or via air pressure) at each bleeder screw. Much like the one-man brake bleeder option above, the vacuum method works well provided you keep an eye on your master cylinder and do not let it run dry, which allows more air into the brake system.
Option 3: Pressure Brake Bleeding
The opposite of vacuum bleeding, pressure bleeding uses a pressurization source (usually compressed air) to force new brake fluid into the system via the master cylinder. This, in turn, pushes the old, contaminated fluid and trapped air out of the system via the bleeder screws at the wheels. Pressure bleeders are often master cylinder specific (due to variances in cap designs) so you may need to own more than one pressure bleeder depending upon the master cylinders used in your vehicles. Or at least purchase the optional master cylinder adapters required to maintain your specific rides.
Option 4: Reverse Brake Bleeding
A rather unique option, reverse brake bleeding requires a specific tool akin to a hand-held vacuum pump, but it works in reverse, pushing the fluid back through the system versus pulling it with vacuum. The main proponent of this method is Phoenix Systems and their line of reverse brake bleeders. The idea here is that vacuum bleeding, much like manual two-person bleeding, forces air downward in the system from the high-mounted master cylinder to the wheels and bleeder screws. If you ever watched a bottle of soda being poured you noticed that the trapped air bubbles easily rise to the top of your glass. Phoenix Systems’ thought here is that it is easier to push the air up, its natural state of direction, than push it down. The tool is very effective for tricky hydraulics like clutch lines and remote master cylinders as well and works great when you want to bleed brakes by yourself.
Option 5: One-Way Brake Bleeder Brake Bleeding This option does not involve any special tools (other than a bottle to catch the old fluid) but does require the installation of special replacement bleeder screws. These bleeders, often referred to by the trade name “speed bleeders” in conversation about them, feature a spring loaded check valve within the body of the bleeder screw itself. To bleed brakes alone simply requires the loosening of the bleeder screw a quarter turn and then you can proceed with pumping the brake pedal. The internal check valve allows the old brake fluid and air to escape, but does not allow any air back in. Once the bleeding process is complete simply tighten the bleeder screw. We offer these check valve style bleeder screws from both Goodridge and from Earl’s.
Option 6: Gravity Brake Bleeding
If you’re not in a hurry and you have a simple brake system, such as a single reservoir master cylinder and four-wheel drum brakes, gravity bleeding your brake system is certainly an option. Gravity bleeding uses the force of gravity to pull the brake fluid through an open system (master cylinder full of fluid with no lid on it and one or more bleeder screws open), removing any air as the fluid escapes the bleeder screws. Gravity bleeding is often employed on freshly installed brake systems that have never had fluid in them. Gravity bleeding brake lines allows the system to “fill” while you can multitask other work in the garage and once there is evidence of fluid at the wheels you can perform your favorite style of brake bleeding. All you need for gravity bleeding is the appropriate bleeder wrench size and a bottle to catch the fluid as it leaves the bleeder screws.
Bleeding Brake System with ABS
If you need to bleed brakes by yourself on an anti-lock brake system (ABS) due to the replacement of a brake caliper or brake hose, you can indeed bleed brakes with ABS system just like any other brake system and with any manner of bleeding (manual, pressure, vacuum, etc.). Now, if you’re going to be bleeding the entire brake system on a vehicle with ABS, such as to flush old fluid from the system, it will depend upon the type of ABS setup and the age of the vehicle. Bleeding brakes on ABS system that is older can usually still be bled completely in a normal manner, but newer ABS systems need to be placed in a service mode that cycles the ABS valves and pump to get that old fluid out of these “hidden passages.” When in doubt, speak with your local service department or consult a shop manual, as you may require a dealer-level diagnostic tool to do this full system bleeding.
When Bleeding Brakes Should the Car Be On?
There is generally no need for the engine to be running when you bleed brakes by yourself. Not only is there danger from moving engine parts close to the front wheels, but overall engine noise and heat as well may make brake bleeding difficult. If you are working on a more modern car where the brake system uses pedal position sensors or fluid level sensors you may wish to bleed brakes by yourself with the ignition key in the “On” position, but again, the engine does not need to be running.
Do You Have to Bleed Brakes After Changing Pads?
Generally, changing brake pads alone does not require bleeding the brakes. However, if other brake components like calipers, hoses, or brake lines are disconnected during the pad replacement, bleeding may be necessary to ensure proper brake function. Additionally, when retracting brake caliper pistons to allow for the full thickness of new pads, many people opt to open the bleeder screws on the caliper versus pushing the old fluid back into the master cylinder. This option is perfectly acceptable, just be sure to close the bleeder screw before fully compressing the piston to prevent air entering the hydraulic system.
Do You Need to Bleed Brakes When Changing Rotors?
Changing rotors typically doesn't require bleeding the brakes unless other brake hydraulic components are disturbed during the rotor replacement, such as the brake caliper or brake hose (never let a caliper hang by the brake hose, use a wire coat hanger or bungee cord to support the caliper’s weight). If there are no signs of brake fluid leaks during rotor replacement and there are no signs of air in the brake lines or master cylinder, bleeding is usually not necessary when changing rotors.
How to Bleed Brakes When Bleeders Are Rusted
A rusted brake bleeder screw is more common than you think. The wheel area sees a lot of moisture and other elements, heat cycling, and more that can quickly cause corrosion around the bleeder screw threads, seizing it in place. It is all too often that we see rounded or chewed up brake bleeder screws from people fighting to get them loose. While you may be wondering how to bleed brakes alone when bleeders won’t open, and some will tell you to crack a brake line to bleed brakes by yourself to bleed brakes without bleeder valves, we feel it is best to address the problem so you can “one man bleed brakes” properly directly at the caliper or wheel cylinder.
There are a few methods you can try to free a seized brake bleeder screw, but first off, be sure to use a proper brake bleeder wrench, which supports the bleeder screw body better than a standard boxed end wrench. If you don’t have access to one, at least use a quality, tight fitting six-point boxed end wrench on the bleeder screw in question. Spray penetrating oil into the threads of the bleeder screw and let it sit, preferably overnight. Repeat the application of the penetrant to keep the threads wet. You want the penetrant to “wick” into the threads and break down the “hold” the corrosion has. Next, using a hammer, give the caliper or wheel cylinder a few hits NEXT to the bleeder screw. Do NOT hit the bleeder screw directly. These hammer blows “shock” the threads and help break apart the corrosion. Attempt to loosen the bleeder screw.
If this process is unsuccessful, you can use a small propane torch to heat the metal around the bleeder screw. This will expand the metal, allowing the bleeder screw to come free. If you must use heat, we highly suggest inspecting all rubber seals in the caliper or wheel cylinder. Either way, once the bleeder screw is free, replace the bleeder screw with a new bleeder screw and apply anti-seize to the threads. We also recommend removing the caliper or wheel cylinder from the vehicle for these steps, which will provide more room to work on the bleeder screw.
Can You Bleed Brakes Without Removing Wheels?
You can bleed brakes by yourself with the wheels on, especially if the brake bleeding is being done during a track session to simply remove boiled fluid and extract air from the system. Provided you have sufficient access to the bleeder screws, bleeding the brakes with the wheels on is perfectly acceptable, just remember that brake fluid can damage painted surfaces, so use a shop towel to cover the wheel surface and use a long hose on your bleeder screw. Obviously, if you’re performing any form of brake work, such as pad replacement, you’re going to have to remove your wheels regardless, but if the circumstances warrant it, you certainly can bleed brakes with wheels on.
Why Are My Brakes Still Soft After Bleeding?
Often you may find that you bleed brakes but still spongy brake pedal when you are done. At the root of this it simply means you still have air trapped in your brake system somewhere or possibly a leak (check all connections on newly installed parts). Depending on the work performed, the air could be trapped in the master cylinder, or closer to the wheels (brake caliper, wheel cylinder, proportioning valve, etc.). Verify your brake calipers are installed properly (not switched side for side or upside down) and the bleeder screw is at the top most portion of the brake system at the wheel. If the master cylinder was replaced, be certain that it was bench bled to remove all air within the master cylinder’s piston before it is installed on the car. Lastly, some systems can be tricky and will not fully bleed via gravity or the manual pedal pumping method. For these applications we strongly suggest a pressure bleeder or a reverse bleeding tool to bleed brakes by yourself.
Brake Bleeding FAQs
Q: Which tool should I buy for bleeding brakes?
The choice of a brake bleeding tool depends on your preferences and needs. Common options include brake bleeder kits, vacuum pumps, pressure bleeding kits, and gravity bleeding. Consider factors like your comfort level, the type of bleeding you'll be doing, and your budget when choosing a tool.
Q: Which bleeding method is the best?
The "best" bleeding method can vary depending on factors like your experience, the tools available, and the vehicle's brake system. No single method is universally superior. Professionals often prefer pressure or vacuum bleeding for efficiency, while DIYers may find manual bleeding methods like two-person or one-person with a bleeder kit more accessible.
Q: How Do Hydraulic Brakes Function?
Actuating your brake lever applies pressure to hydraulic fluid. This non-compressible fluid transmits force through the brake lines to the calipers or wheel cylinders which apply this force to the disc brake rotor or brake drum through the brake lining friction material.
Q: Why is Brake Bleeding Necessary?
Exceeding your brake fluid’s boiling point during track use, a brake system leak, or excessive contamination/moisture in the brake fluid are all possible causes that require the brake’s hydraulic system to be bled, flushing the old fluid and air from the system, and adding clean, fresh fluid in place of it.
Q: How Does Air Infiltrate the Brake System?
Air can enter the brake system when brake pads wear down, lowering the fluid level and allowing air ingress. Any time you open the brake system, like shortening a hydraulic hose or installing new components, air can enter. Damaged calipers or hoses can also cause fluid leakage and air entry.
Q: Is Full Brake System Flushing Necessary?
Brake fluid deteriorates with time and can become contaminated. In some cases, a complete system flush may be needed to maintain optimal brake performance. Contaminated fluid affects viscosity and heat dissipation, potentially damaging the brakes. Most agree for street driven cars have a fluid flush every two years to ensure peak performance.
Q: How Often Should I Bleed My Brakes?
Consider bleeding your brakes if you notice reduced braking performance. Some autocross racers bleed their brakes between runs to remove trapped air and flush overheated brake fluid from their system. Generally, regular brake bleeding is only required when the system has been opened for repairs, such as bleeding brakes after replacing lines.
Q: How Challenging is Brake Bleeding?
Brake bleeding is a relatively straightforward procedure. Once you've accomplished bleeding your own brakes for the first time, you’ll see that there really isn’t much to it and the tool investment is minimal.
Q: What Tools Are Required for Brake Bleeding?
Typically, you'll need brake fluid compatible with your vehicle’s braking system, bleeder screw wrenches/sockets, your choice of brake bleeder (vacuum, pressure, etc.), a brake fluid catch can, and some clear rubber tubing (often included in your brake bleeder kit but we like to have extra in our toolbox). If bench bleeding a master cylinder a bleeder kit with threaded adapter fittings is required to perform this specific task. We also recommend the proportioning valve bleeder tool mentioned earlier if you have a GM PV2 or PV4 style valve.
Q: How Much Brake Fluid to Bleed Brakes?
The amount and type of brake fluid you will need is directly proportional to the size of the brake system’s hydraulic components (calipers, lines, master cylinder) and the work being performed. If you are simply replacing one leaking brake hose, you may need only a pint of fluid. However, if you’re flushing the entire braking system, you may need upwards of two quarts of brake fluid. You’ll find when you bleed brake fluid that you end up using more than the system holds to get all trapped air out.
Q: Can you top up brake fluid without bleeding??
As your brake disc brake pads wear the caliper’s piston extends further outward. This requires additional fluid displacement from the master cylinder and will show as low fluid level in your master cylinder. You can easily top off your brake system without the need for bleeding the brakes. Modern plastic brake fluid reservoirs have a “MIN” and “MAX” marking on the reservoir for fluid level, while older cast iron master cylinders should be filled to within 1/2- to 1/4-inch of the reservoir’s edge.
