It must be connected to a full-time vacuum source such as the
intake manifold.
View page
from the vacuum source in the intake manifold,to various vacuum
operated components
View page
from the intake manifold.
View page
you need manifold vacuum for the brake booster.. (intake
manifold)
View page
If you mean specifically, what type of vacuum, the answer is
manifold vacuum. Manifold vacuum is constant and doesn't, change
with throttle valve opening, the way ported vacuum does.