How to Fix a GM Brake Booster


The power brake booster in your GM vehicle is responsible for providing vacuum pressure to the brake system. This vacuum pressure greatly enhanced the brake force you are able to apply to the brakes when you press on the brake pedal. If you ever experience problems with your brake system, do some troubleshooting to see if the brake booster is the problem. Since the brake booster is a sealed unit, replace the unit if it fails.

Things You'll Need

  • Socket wrench and socket set
  • Tube nut wrench
  • Pliers
  • New brake booster


  • Press on the brake pedal. If the pedal depresses all the way to the floor with little or no resistance, you may have a vacuum leak.

  • Open the hood and check all of the hoses running to the brake booster. Check for any obvious signs of wear or deterioration.

  • Take your vehicle to a lightly traveled road or to an empty parking lot to test the brakes. Traveling no faster than 15 mph, apply the brakes. If excessive brake pedal effort is required to stop, you may have a faulty brake booster. This can be confirmed if your brake pedal travel is to the floor and the hoses connected to the brake booster are not damaged or deteriorated.


  • Slide the tube nut wrench over the brake line where it connects to the brake master cylinder. Orient the wrench so that it fits over the tube nut on the end of the brake line connected to the master cylinder.

  • Turn the tube nut counterclockwise to remove. Note the position and location of each brake line. There are four lines total, one for each wheel. They need to be put back in the exact same location on the brake master cylinder when the brake assembly is reassembled.

  • Unplug the electrical connector running to the brake master cylinder reservoir cap.

  • Remove the bolts holding the brake master cylinder to the brake booster.

  • Pull the master cylinder off the brake booster.

  • Remove the four bolts holding the brake booster to the firewall.

  • Remove the cotter pin holding the brake pedal to brake booster connecting pin in place with a pair of pliers. To remove, simply pull the cotter pin straight out.

  • Pull the brake pedal to brake booster connecting pin out. This will disconnect the brake pedal from the brake system.

  • Pull the brake booster out from inside the engine bay.

  • Install the new brake booster. Installation is the reverse of removal.

Tips & Warnings

  • For specific information on fixing the brake booster on your GM vehicle, consult the particular vehicle's manual (see Resources).
  • After the brake system is reassembled, take your vehicle to a brake shop to have the brake system bled. The brake system will not be fully functional until the system has been bled.
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