Hose and Check Valve

WARNING: This page is about a different car, the 2007 Lincoln Mark LT and 2007 Ford Pickup. 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.
is installed separately (install a new grommet when installing a new check valve).
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 a power assisted brake application with the engine off.