Chevrolet 70 1969 Series, Shop Manual

Page: 226 / 913

BRAKES 5B-33
MOISTURE EJECTOR VALVE
D E SC R IPT IO N A N D O P E R A T IO N
The moisture ejector valve is mounted on a
bracket attached to the cab step support close to
the wet air tank. Moisture is ejected each time the
brakes are released. Air pressure lifts actuator
which lifts plunger, moving inlet valve off seat.
This permits flow of air from wet tank into column
section of valve. When brakes are released, air
pressure snaps actuator back in place, allowing
air and moisture in column to escape past plunger
seat through exhaust port of lower body to atmos­
phere. Spring then returns inlet seat and plunger
seat to "Off" position. This action takes place each
time brakes are applied and released, thereby
operating a continuous process of moisture ejec­
tion from brake air system.
The moisture ejector valve is N O T standard
equipment. It is offered as optional equipment
only on conventional cab models series 70 and 80.
R E P L A C E M E N T (Refer to Fig. 10)
Removal
1. Exhaust air from system.
2. Disconnect air lines at valve.
3. Remove bolts which fasten valve to bracket
on cab step support and remove valve.
Installation
1. Position valve on bracket on cab step sup­
port and secure with attaching bolts.
2. Connect air lines at valve.
3. Build up air pressure in system. Check
operation of valve while applying and releasing
brakes. Check for leaks.
BRAKE APPLICATION VALVES
GENERAL
The brake application valves used on models
covered by this manual all operate on the same
basic principle. The physical shape of the valves
and the methods of mounting differ according to
model. There are two mounting types; tilt cab
models and conventional cab models.
C O N V E N T IO N A L CAB M O D E L S
The application valve on these models is fas­
tened to the cowl (see fig. 2). The valve has two
studs as part of the assembly and one threaded
bolt hole. The valve is mounted inside the cab and
studs extend through holes in cowl. Nuts and lock
washers are installed on studs on engine compart­
ment side along with one bolt to fasten valve se­
curely to cowl. A pedal bracket and pedal assembly
is fastened to the bottom of the application valve
by three bolts. Pedal assembly contacts valve
piston with an upward movement. The exhaust port
is on the back side of the valve and exhaust air es­
capes into engine compartment.
T IL T CAB M O D E L S
The application valve is mounted on a support
bracket in an inverted position inside the cab. The
actuating push rod from the brake pedal extends
up through the bracket into the valve piston cup
as shown in figure 3. A breather tube is installed
in the exhaust opening in place of filter screens
and a hose connected to the tube carries the ex­
haust air down below the cab floor.
APPLICATION VALVE REPLACEMENT
On all conventional cab models both Midland-
Ross and Bendix-Westinghouse application valves
are interchangeable as complete assemblies (in­
cluding pedal). The component parts are not inter­
changeable. All valve ports, mounting holes and
brackets are located in the same relative places
to permit replacement of assemblies regardless
of manufacturer. The following procedures cover­
ing removal and installation, apply to both Bendix-
Westinghouse and Midland-Ross valves.
C O N V E N T I O N A L CAB M O D E L S
Removal
1. To remove pedal only, remove cotter pin
and drive out pedal to bracket pin.
2. To remove pedal and valve as an assembly
block vehicle wheels or hold by some means other
than air brakes.
3. Drain air pressure from brake system.
4. Disconnect air lines from valve both in
cab and in engine compartment.
5. From engine side of cowl, remove one bolt
and two stud nuts which fasten valve to cowl.
6 . Remove pedal and valve assembly from
inside cab.
Installation
1. Place pedal and valve assembly in position
on cowl inside cab.
2. From engine compartment side of cowl,
install one bolt and two stud nuts to fasten valve
to cowl.
3. Connect air lines to valve, both in cab and
in engine compartment.
4. Start engine and build up air pressure to
operating level.
5. Check for leaks.
6 . Test operation of brakes.
N O T E : Various items of special or optional
equipment are often assembled in outlet ports of
the valve, such as low air pressure switch, double
check valve, stop light switch, etc. These items
CHEVROLET SERIES 70 -80 H EAVY DUTY TRUCK S H O P M A N U A L