Brake Booster

WARNING: This page is about a different car, the 2009 Mercury Sable, 2009 Ford Taurus X, and 2009 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.

Inspect the brake booster:

for excessive corrosion or damage.
vacuum connections for leakage.
vacuum hoses for kinks or leakage.
check valve for correct operation.