How Power Brakes Work

Thevacuum boosteris a metal canister that contains a clever valve and a diaphragm. A rod going through the center of the canister connects to themaster cylinder's piston一边和踏板连杆on the other.

Another key part of the power brakes is thecheck valve.

The photo above shows the check valve, which is aone-way valvethat only allows air to be suckedoutof the vacuum booster. If theengineis turned off, or if a leak forms in a vacuum hose, the check valve makes sure that air does not enter the vacuum booster. This is important because the vacuum booster has to be able to provide enough boost for a driver to make several stops in the event that the engine stops running -- you certainly don't want to lose brake function if you run out of gas on the highway. In the next section, we'll see how the booster works (and check out a cool animation!).