You’re slowly driving on the road, and there’s a stop sign ahead. But when you try to stop, your brake pedal sinks into the floor.
What’s going on?
A soft brake may be caused by trapped air in the brake lines, and one of the ways to remove them is by pressure bleeding.
But what is pressure brake bleeding?
Well, pressure brake bleeding pushes air out of the brake valve by applying pressure to the brake reservoir.
In this article, we’ll explain how it works, provide safety tips on brake bleeding and answer some FAQs.
This Article Contains
- How to Pressure Bleed Brakes
- 8 Safety Tips to Follow When Brake Bleeding
- 3 FAQs on Pressure Brake Bleeding
Let’s get started!
How to Pressure Bleed Brakes
The pressure bleeding method applies pressure to the brake master cylinder, which pushes clean fluid into the system and out through the bleeder valve (also known as the bleeder screw or bleed nipple).
Although pressure brake bleeding is simple enough to do it yourself, it’s best to contact a professional if you’re unfamiliar with automotive repairs.
Let’s check out the tools you’ll need to pressure bleed:
A. Tools and Equipment Needed
Here’s a list of tools you’ll need:
- Floor jack and jack stands
- Bleeder wrench
- Several lengths of clear rubber hose
- A pressure brake bleeder kit
- A vacuum pump or turkey baster
- Brake fluid catch bottle
- Clean rags
- New bottles of brake fluid
Note: Always refer to your owner’s manual if you are unsure which brake fluid to use. Using the wrong fluid can reduce braking power and damage your braking system.
B. How It’s Done (Step-by-step)
Here’s how a mechanic would carry out the pressure bleeding process:
Step 1: Jack the vehicle and remove all wheels
First, park the vehicle on a flat surface, jack it up, and remove all the wheels to expose the brake caliper. Then inspect the brake lines for leaks.
Step 2: Identify the correct bleeding sequence and find the bleeder valve
Next, look for the bleed nipple or screw — usually located at the top of the brake caliper.
Then, identify the correct bleeding sequence for your car’s brake system. Typically brake bleeding starts with the brake farthest from the master cylinder, which is the rear brake on the passenger side.
Step 3: Locate the brake master cylinder
Once done, inspect the condition and brake fluid level in the master cylinder reservoir. If the fluid level is low, refill the reservoir until it reaches the maximum threshold.
If the fluid is too old and dirty, conduct a quick brake flush before continuing. This prevents dirt and sludge from clogging the brake lines and the brake reservoir.
Step 4: Prepare the pressure bleeder kit
Next, prepare the brake bleeder kit after inspecting the tubes and connectors for leaks.
To do so, run some clean fluid through the system and test the pressure bleeder to see if it functions properly.
If all is well, assemble the brake bleeder kit and fill the tank with fresh brake fluid.
Step 5: Connect the brake bleeder kit to the master cylinder
Afterward, connect the bleeder kit to the master cylinder with an adapter. The connection must be tight to prevent air from entering the reservoir.
After securing the connector hose, start pumping the pressure tank system to about 15 psi.
Note: Different vehicles may have different pressure requirements, and exceeding them may cause internal damage to the brake system (caliper piston, brake pads, etc.). Always consult your owner’s manual before bleeding brakes.
Step 6: Connect the bleeder tube to the bleeder screw
Next, head to the rear brake and attach the bleeder hose to the bleed screw.
Don’t forget to connect the bleeder hose to a clear catch container to prevent the fluid from spilling onto other components (like brake pads, brake caliper, and drum brakes).
Step 7: Start Bleeding the brakes
Once done, start bleeding the brakes by releasing the screw.
Keep an eye on the old fluid pouring out of the bleeder hose and the pressure reading on the bleeder pump. Once clear brake fluid starts flowing, you can stop the bleeding process. To do so, tighten the bleeder screw and remove the hose.
Step 8: Check the fluid level and pressure of the bleeder pump tank
Before bleeding the remaining brakes, check the brake fluid level and pressure of the pressure bleeder again.
If the fluid level is low, refill the tank with fresh fluid and pump the pressure bleeder again. If the pressure drops during the bleeding process, pump it back again to 15 psi.
Step 9: Repeat steps 6-8 with the other remaining wheels
After checking the brake fluid level and pressure, continue bleeding the rest of your brakes by repeating steps 6 to 8.
Note: These steps will require less brake fluid to flush out the old fluid from the brake system, so you won’t need to refill the tank often. That’s because the brake line gets shorter as the distance between the brakes and the master cylinder reservoir reduces.
Step 10: Observe the brake pedal
Finally, check the brake pedal. If the brake pedal is firm and doesn’t hit the floor at a gentle push, the pressure brake bleeding is successful!
Now, brake bleeding may look simple, but there are some safety notes you should follow.
Let’s find out what they are.
8 Safety Tips to Follow When Brake Bleeding
You shouldn’t take brake bleeding lightly, as it involves hazardous substances (brake fluid).
Here are some safety tips to keep in mind when brake bleeding:
- Wear protective clothing, like safety glasses and gloves
- Park your car in a safe, well-lit, and flat surface
- Shut the engine off and remove the key from the ignition switch
- Ensure all remote starter devices are properly disabled
- Keep the parking brakes engaged until the vehicle is safely lifted and supported
- Use factory-specified lift points when using an automotive jack — lifting a vehicle incorrectly can damage the suspension
- Support the lifted vehicle with jack stands
- Read and follow all safety information and warnings for the equipment you’re using
You should always prioritize your safety whenever working with automotive equipment. Better yet, let a professional handle your repairs.
Now, let’s answer some pressure bleeding related FAQs.
3 FAQs on Pressure Brake Bleeding
Here are some commonly asked questions and answers to help you understand pressure bleeding better.
1. What’s the Difference Between Vacuum and Pressure Bleeding?
The main difference between vacuum and pressure bleeding is where the pressure is applied.
A vacuum pump creates a low pressure region near the bleeder screws. This region acts like a vacuum that sucks out the trapped air and dirty fluid from the brake line.
Meanwhile, pressure bleeding uses a pressurized tank filled with fresh brake fluid that forces new fluid into the braking system and pushes old fluid out of the bleeder screws.
2. How Does Clean Brake Fluid Compare to Old Brake Fluid?
Differentiating between clean brake fluid and old brake fluid is easy.
Old fluid is typically muddy brown or black — sometimes resembling motor oil. You’ll also see debris and grime floating in it. Meanwhile, clean new fluid is clear yellow or amber, with no debris.
Also, old fluid will show a positive result in copper testing, while new fluid won’t. This is because old fluid can dissolve the copper alloy in the inner lining of the brake system.
3. Is There Another Way to Pressure Bleed Brakes?
Yes, there is.
Instead of applying pressure into the brake fluid reservoir, another option is to apply pressure through the bleed screw. This brake bleeding method is called reverse bleeding.
Reverse bleeding forces fresh fluid into the screw, and brake lines, while pushing trapped air and fluid out of the master cylinder. This way, debris from the old fluid goes up and out of the reservoir.
Final Thoughts
Pressure bleeding brakes is more efficient and easier than conventional brake bleeding. However, it involves several specific tools and plenty of brake fluid.
You can follow our guide and safety tips when bleeding your car brakes, but it’s better to let the professionals handle it — like AutoNation Mobile Service!
AutoNation Mobile Service is a mobile automotive repair and maintenance service that you can get with an online booking. Our expert technicians are equipped with all the necessary tools to fix your car in no time!
Contact AutoNation Mobile Service today for a brake bleeding service, and we’ll send our best mechanics to your driveway!