Brake Power Booster Replacement

How to Replace a Power Brake Booster

A power brake booster is designed to assist the driver in the effort to make braking the car easier. By using vacuum from the engine’s intake system and a diaphragm inside the brake booster, the braking force can be more than doubled with minimal effort from the driver. Over the years, a leak can develop in the system. As a result, braking assist is decreased which usually indicates a faulty power brake booster. If this condition exists the first step is to test the booster and replace if needed. If the booster is unable to maintain the vacuum, it has failed. To check this, start the engine, allow to run for fifteen seconds. Shut the engine off and remove the check valve from the booster. 

You should hear vacuum escaping, if not the diaphragm inside the booster has ruptured causing he malfunction. Another sign that the booster is bad is a hard brake pedal, in other words the pedal is hard to push to make the brakes operate. Check to make sure the vacuum hose between the brake booster and the intake manifold is not leaking before replacing the booster. A leaking vacuum hose can cause the same symptoms. Also, don’t panic if this happens. The brakes will still work, but the additional force needed to stop will increase and stopping distance usually increases too.

Park your car on level ground with the engine off and the emergency brake on. Always raise a car according to the manufacturers recommended instructions and secure with jack stands. Also be sure to wear protective clothing, eyewear and gloves.

Tool Needed to Complete this Job:

1. Wrench set

2. Pliers

3. Ratchet and socket set

4. Different length socket extensions


Step 1. Pull the hood release to open the hood, release the secondary safety latch and finish opening the hood, secure with prop rod if needed.

Step 2. The power brake booster is located on the driver’s side of the vehicle under the hood in most cases. It will be mounted between the firewall and the master cylinder.

Step 3. To begin, first remove the large vacuum hose that is attached to the booster.

Step 4. Using your wrenches, unbolt the master cylinder from the brake booster (two bolts).

Step 5. Move the master cylinder just far enough forward so you will have room to remove the booster from its mounting location. (note in some cases the master cylinder will need to be removed).

Step 6. Now to remove the booster. Under the dash board you will see where the brake pedal is attached to a push rod. There will be a retaining clip or cotter pin holding the top of the brake pedal to the push rod. Using pliers, remove the cotter pin or retaining clip.

Step 7. Next, there are four nuts that you will see around where the push rod goes through the firewall. They secure the brake booster to the firewall. Using your sockets and extensions, remove the nuts. This can be sometimes tight and a little frustrating due to the location of the nuts.

Step 8. Once the nuts are removed, return back to the engine area. Again, move the already loosened master cylinder just enough to remove the booster.

Step 9. Slide the booster studs through the firewall and remove it from the vehicle. Install replacement power brake booster and reassemble.

The power brake booster is an important component. As mentioned, there are different ways to check it to be certain it is bad. Always remember, if it does go bad, the brake pedal will be more difficult to press, but the brakes will work. Always drive carefully and leave a safe distance between you and the car in front of you. Any mechanical device can fail without warning. Allowing sufficient distance between you and the vehicle in front of you can provide adequate time to make a safe and logical decision in the event of any type of brake failure.

CAUTION: Brake fluid is very corrosive to your vehicle’s finish. Avoid getting brake fluid on the painted surface of the vehicle. If you do, immediately wipe if off and clean the area with soap and water. It has the ability to remove the paint, so don’t wait. Check the brake pedal operation, it should be normal. Do not move the vehicle until normal brake operation has resumed.   By: Joe Feliciani / AKA jacobandnickolas

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Article first published (Updated 2015-01-06)