Servicing the Bendix Hydrovac
Hydrovac is the trade name for a B-K “one-unit” vacuum power braking
system for use on trucks, tractors or buses equipped with hydraulically actuated
brakes. It combines into one compact assembly a hydraulically actuated control
valve, a tandem-piston power cylinder and a hydraulic cylinder. The assembly
is a complete self contained vacuum power brake “system” which eliminates
the need for external levers or link age. Connections to the vehicle braking
system are entirely hydraulic, consisting of a line from the vehicle brake system
master cylinder to the Hydrovac, and a hydraulic line from the Hydrovac connecting
to the wheel cylinders of the vehicle brake system. Contrasted with conventional
vacuum power brake systems, the Hydrovac is connected hydrauLically instead
of mechanically, both to the vehicle master cylinder and to the wheel cylinders.
Among the advantages which make Hydrovac an important development in vacuum
power braking are:
• Simplified installations.
• External levers and links eliminated.
• Unlimited latitude for location of the Hydrovac.
• Combined physical actuation with power braking as in other B-K systems.
• Unimpaired physical actuation in event the power system fails due to
accidental damage or other cause.
*One waggieltly remarked that. with a long enough hose, the
hydrovac could be “held Ga the drive lap” and sti1l work!