Your brake pedal feels off — spongy even, and your brakes aren’t as responsive.
Why does this happen?
If you have hydraulic brakes (as most passenger vehicles do,) then there may be air trapped inside the brake lines — and an efficient way to remove it is to vacuum bleed the brake system.
This Article Contains
- How to Bleed Brakes With a Vacuum Pump
- 5 Tips to Successfully Bleed Brakes
- 5 FAQs About Vacuum Pump Brake Bleeding
Let’s get vacuuming!
How to Bleed Brakes With a Vacuum Pump
Vacuum brake bleeding is when you remove air from your brake system using a vacuum pump (or vacuum brake bleeder). While you can vacuum bleed by yourself, it’s best to seek professional help if you’re unfamiliar with automotive tools and parts.
That said, let’s find out what you need and how you can vacuum bleed your brake lines:
A. Tools and Equipment Needed
Here’s a list of tools you’ll need to vacuum bleed brakes:
- Floor jack and stands
- Lug wrench
- A vacuum brake bleeder or a hand-held vacuum pump tool
- Several lengths of clear plastic tubing
- A line wrench set
- A plastic catch container
- New bottles of brake liquid
- Bleeder valve adapters, if necessary
- Vehicle repair manual, for references
Note: Always refer to the owner’s manual or the top of your fluid reservoir cap to determine which brake fluid to use. Using the wrong fluid can reduce braking performance and damage the brake system.
B. How It’s Done (Step-by-step)
Here’s how a mechanic would bleed your brakes:
Step 1: Jack the vehicle and remove all wheels
Park your vehicle on a level surface and release the parking brake once the engine cools down. Jack up the vehicle, remove the wheels, go underneath your vehicle, and inspect the brake lines for any leakage.
Step 2: Identify the correct bleeding sequence
Identify the proper bleeding sequence for your vehicle. Typically, it starts from the brake farthest away from the master cylinder, which is the rear brake on the passenger side.
Step 3: Locate the master cylinder, and observe the brake fluid level
Next, check the condition and brake fluid level in the reservoir. If the fluid level is less than the minimum threshold, refill the master cylinder reservoir with fresh brake fluid.
Prepare the brake bleeding kit by connecting the vacuum pump to a container (to catch the pumped-out brake fluid) with a clear plastic tube.
Optional: Do a quick brake flush if you have dirty fluid or if it’s too old. This prevents blockages that may slow down the brake fluid flow.
Step 4: Connect the vacuum hose to the bleeder port
Once done, connect the brake bleeding kit to the bleeder port using another clear plastic tube. Depending on your vehicle’s bleeder port size, adapters can be used to connect the vacuum bleeder to the bleed screw.
Note: The hose should be tightly connected to the bleeder valve to prevent leaking.
Step 5: Loosen the bleed screw and flush out the fluid
Next, use a line screw to loosen the bleeder valve by half an inch.
Using the vacuum pump, generate a constant pressure of about 90 PSI. This creates a vacuum inside the hose, which sucks out the old fluid and air.
After a few minutes, clear hydraulic fluid with no air bubbles should start flowing. This means there’s no air left in the brake line. Release the vacuum bleeder from the bleed valve and close the bleeder screw.
Step 6: Repeat steps 3-5 on the remaining wheels
Repeat these steps on the remaining wheels. Also, constantly check the fluid level in the master cylinder to ensure the brake fluid reservoir doesn’t dry up.
Step 7: Observe the brake pedal
Finally, check the brake pedal after all the brakes are vacuum bled. If the brake pedal is firm and doesn’t touch the floor when you press it gently, the brake bleeding is a success.
But, if the pedal is still soft and spongy, the brake bleeding process may need a redo.
So what can you do to prevent this from happening?
5 Tips to Successfully Bleed Brakes
Brake bleeding can become tedious if you get it wrong, as you’ll have to repeat the steps until all air in your hydraulic system is gone.
To avoid that, here are some tips to ensure successful vacuum bleeding:
1. Check Your Manufacturer’s Recommendations
Different vehicles may have different bleeding sequences, so it’s best to check with the owner’s manual to find the correct order.
If you bleed brakes in the wrong order, there’s a chance that some air might be left in the brake line. This can affect your car’s braking performance.
2. Use Fresh Brake Fluid
Always use freshly opened hydraulic brake fluid when refilling or bleeding brakes.
Using brake fluid from an old bottle (even if it’s only a week old) causes damage to your brake system. This is because once you open a bottle of brake fluid, it immediately accumulates humidity and starts losing its quality.
3. Apply Teflon Tape and Grease to the Bleeder Screws (Optional)
In some cases, hydraulic brake fluid can leak through the bleeder screws. To prevent that, you can apply a few rounds of Teflon tape onto the brake caliper threads and then replace the bleed screw.
4. Check the Brake Fluid Level in the Master Cylinder
When brake bleeding, always ensure the master cylinder is full. Never let the fluid level drop too low. If the brake fluid reservoir runs dry, it may cause complete brake failure.
5. Wear Protective Clothing and Other Gear
Brake fluid is hygroscopic, meaning that it absorbs atmospheric water. Once this happens, the liquid becomes dangerous to the human body and can ruin your car’s paint.
It’s best to wear protective gear like safety glasses and gloves. You should also keep a bucket of water and some shop towels close by to wipe off any fluid that gets onto your vehicle.
Now, time to answer some related FAQs.
5 FAQs About Vacuum Pump Brake Bleeding
Here are answers to some commonly asked questions to help you understand brake bleeding better:
1. Is Brake Bleeding Necessary?
Yes, it is.
Brake bleeding helps remove trapped air from the brake line to get your brakes functioning in top condition. It’s usually done after every hydraulic system repair, even if you just get a brake caliper or brake pad replacement.
2. How Often Should I Replace the Brake Fluid?
Ideally, you should replace your hydraulic brake fluid every two to three years.
Like any other fluid in your car, hydraulic fluid degrades, especially when exposed to air and dirt.
Unchanged old brake fluid can severely reduce braking power. Plus, foreign pollutants in the dirty fluid can ruin the rubber seals in your brake line and slows down brake fluid flow.
3. How Does the Vacuum Pump Brake Bleeder Work?
Vacuum bleeding uses a vacuum pump to siphon the old brake fluid and air.
When pumping the device, it creates a vacuum region in the connecting tubes. This forces old brake fluid and air out of the bleeder valve and into the catch container.
4. Can I Vacuum Bleed the Master Cylinder?
Yes, you can.
To do so, you’ll have to connect the vacuum pump brake bleeder to the cylinder ports of the brake fluid reservoir and then bleed the master cylinder like how you’d bleed your brakes.
This procedure is done after a master cylinder replacement. Brake bleeding helps removes air from the cylinder ports and ensures your brake system works properly.
5. Are There Other Ways to Bleed Brakes?
There are generally four other methods that you can use to bleed your brakes:
- Manual Bleeding: A two-person job where one controls the brakes while the other works on releasing and tightening the bleeder valve.
- Gravity Bleeding: Uses gravity to drain the brake fluid through open valves slowly.
- Pressure Bleeding: A special pressure bleeder kit is required to pump old fluid and trapped air through the master cylinder reservoir and out of the bleeder valves.
- Reverse Bleeding: Needs a special pressure injector tool that forces air bubbles through the brake lines and out of the master cylinder. Brakes should be flushed before reverse bleeding to prevent dirt and gunk in the old fluid from passing through ABS components and the master cylinder on their way to the reservoir.
Vacuum bleeding brakes is more efficient compared to traditional brake bleeding. It does require specific tools and knowledge, but it gets the job done in a short amount of time.
You can follow our guide and tips to bleed your car brakes, but it’s best to leave any automotive repairs to a professional — like RepairSmith!
RepairSmith is a mobile automotive repair service readily available at the tip of your fingers. Our technicians are equipped with all the automotive tools needed to perform a majority of repairs.
Contact RepairSmith today, and we’ll send our best mechanics to get your brakes bled right in your driveway!