E 350 V8-5.4L (2008)
Vacuum Brake Booster: Description and Operation
Brake Booster
The power brake actuation system consists of the following components:
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Brake booster assembly
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Brake booster vacuum fitting
The brake booster uses engine vacuum from the intake manifold to create a partial vacuum inside the vacuum booster on both sides of the diaphragm.
When the brake pedal is pressed, the booster rod opens a valve, allowing air to enter the booster on one side of the diaphragm while sealing off the
opposite side. This increases pressure on that side of the diaphragm so that it helps push the rod, which in turn pushes the piston in the master cylinder.
As the brake pedal is released, the valve seals off the outside air supply while opening the vacuum valve. This restores vacuum to both sides of the
diaphragm, allowing everything to return to its original position.
