Chevrolet 30 Series 1967 Service Manual page 264

BRAKES 5-50
SAFETY VALVE
Every Year or 50,000 Miles:
The safety valve should be removed, disassembled and
thoroughly cleaned. Adjust to 150 psi blow-off pressure
after reassembly.
SINGLE CHECK VALVE
Every Year or 50,000 Miles:
The check valve should be dismantled and thoroughly
cleaned.
LOW PRESSURE INDICATOR
Every Month or 10,000 Miles:
Check the electrical connections and the air pressure
at which the contacts close. This should be 58 to 65 psi.
If above or below this range, replace switch.
AIR COMPRESSOR
Removal
These instructions are general and in some cases ad­
ditional precautions must be taken.
1. Drain air brake system.
2. If water cooled type compressor, drain engine cool­
ing system, compressor cylinder head and block.
3. Disconnect all air lines, water and oil lines to and
from compressor.
4. Remove compressor mounting bolts and compressor
from engine.
5. Use a gear-puller to remove the gear or pulley
from compressor crankshaft.
Installation (Cleaning and Inspection)
1. Clean oil supply line. Before connecting this line to
the compressor run the engine briefly to be sure oil
is flowing freely through the supply line.
2. Clean the oil return line or return passages through
the brackets; these passages must be unrestricted so
oil can return to the engine.
3. Prelubricate compressor cylinder walls and bearings
with clean engine oil before assembling compressor.
4. Always use a new mounting gasket and be sure oil
hole in gasket and compressor is properly aligned
with oil supply line.
5. Inspect pulley or gear and associated parts for wear
or damage. They must be a neat fit on compressor
crankshaft. Replace pulley or gear if worn or
damaged.
. Install pulley or gear on compressor crankshaft
6
making sure it properly contacts the shaft and does
not ride the key. Tighten crankshaft nut securely
and install cotter pin.
7. Be sure the air cleaner is clean and properly in­
stalled. If the compressor intake is connected to
either the engine air cleaner or supercharger, these
connections must be tight with no leakage.
. Clean or replace any damage or dirty air or water
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lines which may be corroded, before connecting them
AIR GAUGE
Check the accuracy of the air gauge semi-annually.
The simplest way to do this is to compare it with another
gauge known to be accurate.
Dash gauges may lose their accuracy after long periods
of service and may require replacing. Continued use of
dash gauges showing error of more than 5 psi high or
low is not recommended. Many state motor vehicle codes
require gauge accuracy within
PRESSURE PROTECTION VALVE
Pressure protection valve service procedures are
outlined under Service Operations in this section.
AIR BRAKE ADJUSTMENTS
Air brake adjustments are described under Service
Operations in this section.
SERVICE OPERATIONS
to the compressor.
gasket.
9. Align
tension.
10. Tighten mounting bolts securely and evenly.
11. After installation run compressor and check for air,
oil, or water leaks at compressor connections. Also
check for noisy operation.
RELAY VALVE
The relay valve is normally mounted to operate the
brakes on the rear axle or axles of six wheel air braked
tractors or trucks and long wheel base trucks. It is con­
trolled by the brake valve and delivers the same air
pressure to the brake actuators it controls as is being
delivered to the relay valve by the brake valve. The relay
valve has a direct compressed air supply as can be noted
in Figure 79. It operates as a remotely controlled high
capacity brake valve.
Type R - l Relay Valves are mounted on a reservoir.
Type R l-C Relay Valves are mounted away from, but
connected to, a reservoir by tubing. Both types operate
in a sim ilar manner.
Leakage Tests
1. Fully charge air brake system.
2. Make several service brake applications and check
for prompt application and release at all wheels.
3. With service brakes released, coat the exhaust port
of the relay valve with soap suds. A maximum leak­
age as indicated by a one inch soap bubble in not less
than three seconds is permissible.
4. Make and hold a service brake application and coat
the exhaust port of the relay valve with soap suds.
A maximum leakage as indicated by a one inch soap
bubble in not less than two seconds is permissible.
5. Release the brakes.
leakage is excessive, replace relay valve, or repair
1 0
Use a new discharge fitting
compressor drive and adjust proper belt
If valve does not function as described above, or if
or replace worn or damaged parts, in which case the
following information should prove to be helpful.
percent.
CHEVROLET TRUCK SERVICE M ANUAL