Vacuum Brake Booster

This booster is a tandem vacuum unit with a diaphragm effective diameter 8.072" (205 mm) + 9.056" (230 mm). In normal operating mode, with the service brakes in the released position, the tandem vacuum booster operates with vacuum on both sides of it's diaphragms. When the brakes are applied, air at atmospheric pressure is admitted to both sides of the diaphragm to provide the power assist. When the service brake is released, the atmospheric air is shut off from both sides of the diaphragm. The air is then drawn from the booster through the vacuum check valve to the vacuum source.