GM Service Manual Online
For 1990-2009 cars only

Vacuum Booster

Important: 

   • Replace all of the components that are included in the repair kits in order to service this booster.
   • Lubricate the rubber parts with silicone grease in order to ease assembly. The silicone grease is provided in the service kits.
   • Do not use lubricated compressed air on the brake parts. This action may cause damage to the rubber parts.
   • If you remove or disconnect any hydraulic component, you may have to bleed all or part of the brake system.
   • The specified torque values are for fasteners that are dry and that are not lubricated.
   • Perform the service operations on a clean bench that is free from all mineral oil materials.

This vacuum booster is a tandem vacuum suspended unit. When the service brakes are released during normal operation, the tandem vacuum booster operates with vacuum on both sides of the diaphragms. When the brakes are applied, air at atmospheric pressure is admitted to one side of each diaphragm in order to provide the power assist. When the service brake releases, the atmospheric air shuts off from one side of each diaphragm. The air then draws from the booster through the vacuum check valve to the vacuum source.