Chevrolet 10 Series 1968, Service Manual, Page: 304 / 713

BRAKES 5-61
crankshaft. Replace pulley or gear if worn or dam­
aged.
6. Install pulley or gear on compressor crankshaft
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.
8. Clean or replace any damage or dirty air or water
lines which may be corroded, before connecting them
to the compressor. Use a new discharge fitting
gasket.
9. Align compressor drive and adjust proper belt ten­
sion.
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 re ­
lay valve has a direct compressed air supply as can be
noted in Figure 92. 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 similar 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.
If valve does not function as described above, or if
leakage is excessive, replace relay valve, or repair
or replace worn or damaged parts, in which case the
following information should prove to be helpful.
Rem oval
1. Block or hold vehicle by a means other than air
brakes.
2. Open drain cocks and exhaust air pressure from air
brake system.
3. Disconnect air lines from relay valve.
4. Remove mounting bolts and remove relay valve.
Disassem bly
1. Remove actuator adapter and its gasket.
2. Remove cover, diaphragm, diaphragm ring, bleeder
passage grommet, and bleeder passage filter.
3. Remove diaphragm guide and grommet.
4. Remove supply valve cap nut and grommet.
5. Remove supply valve spring, seat retainer spring,
supply valve, supply valve seat, and supply valve seat
grommet.
6. Remove exhaust strainer.
C leaning and Inspection of Parts
lo Wash all metal parts in a cleaning solvent such as
alcohol or kerosene and dry them thoroughly. Keep
parts submerged in solvent for shortest possible
time to avoid damage to materials.
2. Inspect all moving parts for wear or damage and
bores for out of round condition.
3. Inspect diaphragm and bonded rubber valve for wear
or deterioration.
4. Inspect spring for breaks or deterioration.
5. Inspect valve seats for nicks or burrs.
6. Inspect bleeder passage in body, diaphragm ring and
cover and clear any restrictions noted.
7. Clean or replace strainer and filter elements.
8. Replace any parts which are no longer serviceable
by these inspections.
Assem bly
Prior to assembly, lubricate lightly the following sur­
faces with Lubriplate or equivalent.
a. All grommets.
b. Diaphragm guide bore of relay valve.
c. Outside diameter and supply valve stem bore of
diaphragm guide.
d. Supply valve seat bore of relay valve body.
1. Install exhaust port strainer. Be sure retaining ring
is firm ly seated in its groove.
2. Install supply valve seat grommet and supply valve
seat. Note that seat is firm ly seated on shoulder in
body.
3. Install supply valve, supply valve spring and seat
retainer spring.
4. Install grommet on supply valve cap nut.
5. Install and tighten the supply valve cap nut.
6. Turn body over.
7. Place grommet on diaphragm guide and install guide
in relay valve body. Note that guide is neat sliding
fit in body bore and on supply valve stem.
8. Install bleeder passage grommet in body.
9* Install diaphragm ring.
10. Install relay diaphragm.
11. Install bleeder passage filter in cover and position
cover on body.
NOTE:
Bleeder passage openings in body, dia­
phragm ring, diaphragm, and cover must line up.
12. Install lock washers and cap screws and tighten them
evenly and securely.
13. Install gasket and actuator adapter.
14. Tighten cap screws evenly and securely.
Installation
1. Clean or replace lines to relay valve.
2. Mount relay valve securely.
3. Connect air lines.
4. Test relay valve for serviceability as outlined in
"Operating and Leakage Test Section."
CHEVROLET TRUCK SERVICE MANUAL