Hose and Check Valve

WARNING: This page is about a different car, the 2005 Ford RV Cutaway, 2005 Ford Econoline, 2005 Ford E450 Super Duty, and 2005 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

The power brake booster check valve:

is located on the front of the power brake booster.
check valve and grommet can be installed new separately.
is positioned between the power brake booster and the power brake booster hose.
closes when the engine is turned off.
in the closed position, traps engine vacuum in the power brake booster.
retains vacuum to provide several power-assisted brake applications with the engine off.