Corvette V8-350 5.7L DOHC VIN J MFI (1990)
Fig. 4 Delco-Moraine Single Diaphragm Booster
This power brake unit is a suspended type vacuum brake booster which utilizes engine intake manifold vacuum and atmospheric pressure to assist in
braking, Fig. 4.
The unit consists of a vacuum power section and a hydraulic master cylinder section. The vacuum power section contains a power piston with rolling
diaphragm mechanism and power piston return spring.
The control valve consists of an air valve and floating vacuum control valve assembly. The reaction mechanism consists of a hydraulic piston, reaction
plate and a series of levers. The valve operating rod, (which operates the air valve), projects from the power section and is connected to the brake pedal
linkage.
A vacuum check valve, attached to the front vacuum chamber and connected to the intake manifold, traps vacuum in the power unit at the highest level
of vacuum. In addition, some models are equipped with a vacuum switch mounted on the front housing. The switch serves to illuminate the brake failure
warning lamp when vacuum applied to the booster falls below a predetermined level.