The power brake booster uses engine manifold vacuum against a diaphragm to assist in the application of the brakes. The vacuum is regulated to be proportional to the pressure placed on the pedal.
CAUTION
Properly disarm the air bag on vehicles equipped with the SRS system. Failure
to do so can cause serious injury. The procedure can be found in Section 6 of
this manual under the heading "Supplemental Restraint System''.