Ask The NAPA Experts: How to Replace a Brake Booster

Today, there are hardly any vehicles left on the road that don’t have some sort of power brake system. There’s nothing wrong with manual brakes, but power brakes sure make stopping a whole lot easier. But, if there’s a problem with the power brake booster, it can take a lot more effort to stop than you are accustomed to using. 

You should take all brake system problems seriously and repair them immediately. Let’s ask the NAPA experts how to replace brake booster parts so you can stop with confidence again.

What Is a Power Brake Booster?

A power brake booster takes the effort you put into pushing the brake pedal and multiplies it. This makes it easier for the driver to push the brake pedal, while putting a much greater amount of pressure into the hydraulic brake system.

Most power brake boosters are located between the firewall and the brake master cylinder. It is usually a wide but short round cylinder with a vacuum hose attached to it. The vacuum hose supplies the engine vacuum, which operates the power brake booster. Some vehicles use a hydraulic power brake booster powered by the power steering pump. Vehicles such as late model GM trucks, full-size vans and SUVs use a Hydro-Boost brake system. 

Can You Fix a Power Brake Booster?

Depending on the type of power brake booster, it is possible to rebuild it. You can rebuild a hydraulic power brake booster with new seals and a vacuum power brake booster with a new diaphragm and seals. 

Power brake booster repair requires complete disassembly of the unit, cleaning, replacing worn parts and careful reassembly for leak-free operation. While the process is possible for a DIYer, it is far more simple to just buy a remanufactured unit or to seek professional help from your nearest NAPA Auto Care center.

Steps for Brake Booster Replacement 

Below is a general overview of what it takes to replace brake booster units in most vehicles. For the exact procedure to follow for your own brake booster repair, make sure to get a repair manual.

Most brake boosters are vacuum powered. The procedure for a hydraulic brake booster is similar to a vacuum booster. The main difference is the addition of hydraulic feed and return lines plus the need to bleed the system of air bubbles afterward.

1. With the engine off, pump the brake pedal several times until the pedal is firm. This relieves the pressure from the power brake booster.
2. Open the hood to locate the brake master cylinder on the vehicle firewall. Usually, you can spot the brake fluid reservoir on top of the master cylinder. The power brake booster is located between the master cylinder and the firewall.
3. If there is an electrical connection to the brake master cylinder (usually for the brake fluid warning sensor), disconnect it now.
4. Disconnect the lines to the brake booster.
   1. If the power brake booster is vacuum operated, disconnect the vacuum hose.
   2. If the power brake booster is hydraulically operated, place a catch pan under the brake booster area, then disconnect the pressure feed and return lines.

You will likely need a line wrench to prevent damaging the fittings. Gently move the vacuum hose or hydraulic lines away from the power brake booster.

1. Unbolt the master cylinder from the power brake booster. Typically, there are two studs with nuts holding the master cylinder to the power brake booster.
2. Move the master cylinder gently out of the way if possible. Ideally, you can leave the brake lines attached to the master cylinder as you work, but if space is too cramped, you may have to remove the master cylinder to access the power brake booster. If that is the case, budget your time and resources to add a brake fluid bleed procedure after the power brake booster task is complete.
3. Move inside the vehicle underneath the steering wheel. This is where an under dash creeper comes in handy. 
4. Depending on the brake pedal design, the brake pedal linkage will need disconnected from the brake booster. The brake pedal pushrod is possibly connected via either a threaded end or a round eyelet. Refer to a vehicle specific repair manual for the exact procedure for disconnecting your brake pedal pushrod.
5. Commonly, there are two or four studs with nuts holding the brake booster to the brake pedal linkage. Remove the nuts to free the power brake booster from the brake pedal and firewall.
6. You should now have the ability to remove the power brake booster from the engine compartment.
7. Inspect the old power brake booster for any signs of brake fluid at the area where the brake master cylinder attaches. You should never have any brake fluid on or inside the power brake booster. Signs of brake fluid means the master cylinder has a leak, which will likely damage the new power brake booster. 
8. Install the new power brake booster, taking care to align the mounting studs to the openings in the firewall.
9. Move back inside the vehicle underneath the steering wheel and reinstall the brake booster mounting nuts.
10. Reinstall the brake pedal linkage to the brake booster.
11. Move to the engine compartment and reattach the master cylinder to the power brake booster. Take care to not bend any brake lines. Reinstall the master cylinder retaining hardware.
12. Reconnect the lines to the brake booster.
    1. For vacuum powered brakes, reconnect the vacuum hose.
    2. For hydraulic powered brakes, reconnect the pressure and return lines. Remember that you will need to top off the power steering fluid and bleed any air from the hydraulic system.
13. Reconnect any electrical connections to the brake master cylinder.
14. Check the brake fluid level as you are right there anyway. It is also a great time to consider removing some of the old brake fluid and topping it off with fresh fluid.

Once the new power brake booster is installed and everything is put back together, get behind the wheel to start the engine. Pump the brakes a few times to verify that the booster is working correctly and the brake pedal is getting assisted. Put the vehicle in gear and drive slowly. Then, apply the brakes to verify everything is working as it should. If the vehicle does not stop promptly, you may have other brake system issues that need further diagnosis. 

How Much Does It Cost to Replace a Brake Booster?

So, how much to replace the brake booster on your vehicle? On average, brake booster replacement costs between $700 and $1,200. The type of brake booster (vacuum power brake booster or hydraulic power brake booster) makes a difference in overall cost. 

Also, how the brake booster is packaged in the vehicle will make a difference in labor costs. A minivan with the power brake booster buried under the windshield is more labor intensive than a full-size truck with the power brake booster sitting out in the open on the firewall. For a more accurate estimate, check out the NAPA Auto Care Repair Estimator.

If power brake booster repair is beyond your skill set or if you just don’t have the time, you can always visit your local NAPA Auto Care center. Our team of ASE-certified technicians have the expertise and the training to diagnose your brake system issues. As a bonus, your repair is covered by our free 24-Month/24,000-Mile Peace of Mind Warranty (parts and labor on qualifying repairs and services), which spans across the entire nationwide NAPA Network, including 17,000+ NAPA Auto Care center locations.

Featured image courtesy of pxhere.