Sentra Wagon FWD L4-1597cc 1.6L SOHC (GA16i) (1989)
Power Brake Assist: Description and Operation
The vacuum assist diaphragm assembly multiplies the force exerted on the master cylinder piston in order to increase the hydraulic pressure delivered
to the wheel calipers or cylinders, while decreasing the effort necessary to obtain acceptable stopping performance.
Vacuum assist units get their energy by opposing engine vacuum to atmospheric pressure. A piston, cylinder and flexible diaphragm utilize this energy
to provide brake assistance. The diaphragm is balanced with engine vacuum until brake pedal is depressed, allowing atmospheric pressure to unbalance
the unit and apply force to the brake system.