Chevrolet 30 Series 1967 Service Manual page 263

check the discharge line for carbon. If excessive carbon
is found in either check, the cylinder head or discharge
line should be cleaned or replaced.
100,000 Miles:
Depending upon operating conditions and experience,
disassemble compressor, clean and inspect all parts
thoroughly. Repair or replace all worn or damaged parts.
IMPORTANT: Should it be necessary to drain
the engine cooling system to prevent damage
from freezing, water cooled compressors must
be drained as both cylinder block and cylinder
head are water cooled. Use drain cock or re­
move head and/or block pipe plugs.
INSPECTION
It is of the utmost importance that the compressor is
taking in clean air. The air strainer must be properly
installed and kept clean. If the compressor intake is con­
nected to the engine air cleaner, etc., these connections
must be properly installed and maintained.
Check compressor mountings to be sure they are
secure. Check drive for proper alignment, belt tension,
etc. Inspect oil supply and return lines. Be sure these
lines are properly installed and that the compressor is
getting the proper supply of oil, and just as important,
that the oil is returning to the engine properly.
Check water lines to and from compressor if a water-
cooled type.
If the compressor is air-cooled, check to be sure the
engine fan b l a s t is
unrestricted.
Check unloader mechanism for operation.
TESTS (AIR LEAKAGE)
Leakage past the discharge valves can be detected by
removing the discharge line, applying shop air back
through the discharge port and listening for escaping
air. Also the discharge valves and the unloader pistons
can be checked for leakage by building up the air system
until the governor cuts out, then stopping the engine. With
the engine stopped, carefully listen for escaping air at the
intake. To pin-point leakage if noted, squirt soapy water
around the loader pistons. If there is no noticeable leak­
age at the unloader pistons, the discharge valves may be
leaking.
If the compressor does not function as described above,
or leakage is excessive, the compressor should be re­
paired with genuine service parts, in which case the fol­
lowing information should prove helpful.
GOVERNOR
Every Six Months or 15,000 Miles:
Remove both governor air filters and wash thoroughly
in cleaning solvent that is known to have no detrimental
effect on metal, nylon, or rubber material.
BRAKE VALVE
Every Year or 50,000 Miles:
Disassemble brake valve and clean all parts. Install
new inlet valves and piston seal.
flowing by th e compressor
RELAY VALVE
Once each year the relay valve should be disassembled
and cleaned. Rubber parts and parts subject to wear
should be replaced if worn or damaged. Strainers at
relay diaphragm bleeder passage and exhaust port should
be cleaned or replaced.
function as described under Service Checks—Relay Valve,
disassemble the valve and clean all parts.
QUICK RELEASE VALVE
Every Year or 50,000 Miles
Disassemble valve, clean all parts and replace the
diaphragm.
BRAKE CHAMBERS
Every Month or 2,000 Miles:
Check travel of brake chamber push rods and adjust
brakes if necessary. Push rod travel should be kept at
the minimum without brakes dragging.
Excessive travel shortens the service life of brake
chamber diaphragms and also results in slow braking
response.
Every Year or 50,000 Miles:
Disassemble brake chambers and clean all parts.
Install new diaphragms. When replacing release springs
be sure to use the correct spring, otherwise uneven
braking will result.
SLACK ADJUSTERS
The slack adjusters for 1967 are fully packed with
grease when assembled and need no periodic lubrication.
If the slack adjuster is disassembled for any reason
it must be repacked with grease in the following way:
1. Remove one plug from the slack adjuster side plate.
2. Using a pressure grease gun, inject grease into the
hole in side cover while turning the worm shaft
approximately 50 revolutions in one direction.
3. Install side plate plug securely.
4. Rotate wormshaft about 3 revolutions in the opposite
direction.
5. Refer to Section 0 -
information.
RESERVOIRS
Drain air reservoirs regularly, as required. Local
conditions govern frequency; in dry climates, for ex­
ample, once a month may be sufficient, while in humid
areas it may be necessary to drain reservoirs daily.
Satisfactory draining is only accomplished by leaving
the drain cock open after the air has escaped and until
all drainage stops.
Many an efficient reservoir arrangement has failed in
its normal function through haphazard maintenance.
DRAIN COCKS
All drain cocks should be periodically checked for
leakage, both for leakage past the key and leakage through
the body around the key. Leakage of more than a one inch
soap bubble in one second is not permissible.
BRAKES 5-49
If the relay valve does not
Lubrication for additional
CHEVROLET TRUCK SERVICE M ANUAL