Chevrolet Light Duty Truck 1973 Service Manual page 327

RESERVOIR COVER
FLUID RESERVOIRS
FLOATING PISTON STOP BOLT
FLOATING PISTON ASSEMBLY
RELEASED (Figs. 86 and 87)
At the released position the air valve is seated on the
floating control valve. Air at atmospheric pressure, which
enters through the filter element in the tube extension of
the power piston, is shut off at the air valve. The floating
control valve is held away from the valve seat in the
power piston insert. Vacuum is present in the space on
FRONT SHELL
COMPENSATING PORT
PRIMARY PISTON ASSEMBLY
Fig. 86--Typical Power Unit
REAR SHELL
POWER PISTON DIAPHRAGM
REACTION RETAINER
POWER PISTON INSERT
REACTION LEVER
FLOATING CONTROL VALVE
AIR VALVE
REACTION PLATE
POWER PISTON RETURN SPRING
MASTER CYLINDER PUSH ROD
SUPPORT PLATE
AIR FILTER
Released
both sides of the power piston. Any air in the system is
drawn through a small passage in the power piston, over
the valve seat in the power piston insert, and then
through a passage in the power piston insert. From here
it travels through a hole in the power piston support
plate into the space in front of the power piston. It is
then drawn through the check valve and into the engine
intake manifold.
BRAKES 5-61
REACTION SPRING
PUSH ROD
AIR FILTER SILENCER
LIGHT DUTY TRUCK SERVICE MANUAL