Chevrolet 30 Series 1967 Service Manual page 275

valve seat thoroughly. Check the body and spring cage for
cracks. Be sure the exhaust port in the spring cage is
not plugged.
Assembly
1. Place the ball valve in the body of the safety valve.
2. Place spring release pin and spring seat in spring
cage with the adjusting screw assembly. Position
the spring seat over the ball valve and screw the
spring cage to the body.
Installation
Screw safety valve in place in proper reservoir line.
Tests and Adjustments of Rebuilt Unit
Both operating and leakage tests,
Service Check, must be made after rebuilding the safety
v a l v e and the valve m u s t
specifications:
1. Leakage at the exhaust port should not exceed a one-
inch soap bubble in one second.
2. The safety valve should be set to "blow off" at ap­
proximately 150 PSI. The pressure setting may be
adjusted by loosening the lock nut and turning the
adjusting screw. Turning the adjusting screw clock­
wise, raises the pressure setting. Turning the
adjusting screw counter-clockwise, lowers the pres­
sure setting. The setting of the adjusting screw
should be locked by lightening the adjusting screw
lock nut after each adjustment. An accurate test
gauge should be used when adjusting the pressure
setting of the safety valve.
SINGLE CHECK VALVE
Removal
1. Exhaust air from brake system.
2. Remove air lines at single check valve and remove
valve (fig. 96).
Disassembly
Unscrew cap nut from body and remove grommet. Re­
move disc valve, spring, and valve stop bushing from
body.
Cleaning and Inspection of Parts
Clean all parts in cleaning solvent. Inspect disc valve
and seat for corrosion. Inspect body and cap nut for
cracks or damage. If any damage is present, replace
entire valve assembly.
Assembly
1. Position valve stop bushing, spring and disc valve in
body.
Fig . 96-*-Single Check V a lve
indicated under
meet the f o l l o w i n g
<-
2. Install grommet on cap nut and screw cap nut into
body and tighten securely.
Installation
Position valve in place with arrow on side of body in­
dicating direction of air flow. Secure air lines to each
end of the valve.
Testing Rebuilt Unit
Both operation and leakage tests must be made as out­
lined under Service Checks—Single Check Valve.
LOW PRESSURE INDICATOR SWITCH
Removal
1. Make certain ignition is off.
2. Exhaust all air from brake system.
3. Disconnect the electrical connections at the low
pressure indicator switch.
4. Disconnect the air line to the low pressure indicator
switch.
Installation
1. Mount indicator in place .
2. Attach and tighten mounting nut and connect air line.
3. Attach and tighten electrical connection.
Testing Replacement Unit
Both operating and leakage tests must be made as out­
lined under Service Checks—Low Pressure Indicator.
AIR GAUGE
Removal
1. Remove air line and lamp socket.
2. Remove four instrument panel backing plate screws
and remove backing plate from vehicle.
3. Separate gauge from backing plate by removing two
retaining screws.
Testing Replacement Unit
The simplest way to test any dash pressure gage is to
compare it with a special test gauge that is known to be
accurate. By substituting one gauge for another at one
given point in the air brake system, this comparison can
be made.
Installation
1. Attach gauge to instrument panel backing plate using
original screws or equivalent.
UPPERBODY
SPRING
SPRING CAP
DIAPHRAGM
LOWER BODY
Fig . 97—Pressure Protection V a lv e —Cross Section
BRAKES 5-61
CHEVROLET TRUCK SERVICE MANUAL