Chevrolet 70 1969 Series, Shop Manual

Page: 639 / 913

POWER BRAKE 5-30
AIR COMPRESSORS AND GOVERNORS
AIR COMPRESSOR AND GOVERNOR
(MIDLAND-ROSS TY P E )
INDEX
Subj ect
D e sc rip tio n and O peration of
C o m p re s s o r and G o v e r n o r . . .
T ro u blesho otin g C h a rt .................
D is a s s e m b ly of C o m p re s s o r
and G o v ern o r ...................................
C leaning, Inspection and R ep air
P ag e No.
5-30
5-30
5-32
5-35
Subj ect P ag e No.
A ssem b ly of C o m p re s s o r and
G o v ern o r ............................................................. 5-38
T estin g R ebuilt C o m p r e s s o r ...................... 5-41
G o v ern o r A d j u s t m e n t ....................................... 5-42
S p e c i f i c a t i o n s ........................................................ 5-42
DESCRIPTION AND OPERATION OF COMPRESSOR AND GOVERNOR
C om pressor illustrated in Figure 1 is a 7 -1/4 - cubic-
foot water-cooled unit. T he air-cooled unit is sim ilar to
the water-cooled unit shown, except the air-cooled unit
has external cooling fins. The bore size in the 12-
cubic-foot unit is larger than in the 7 - 1 / 4 cubic-foot
unit. Inform ation in text applies to both 7 - 1 / 4 and 12-
cubic-foot com pressors unless otherwise noted in this pub­
lication.
Air com pressor is a two cylinder, reciprocating type
unit. C om pressor is lubricated by the engine lubrication
system, and the water-cooled unit is cooled by the engine
cooling system.
C om pressor governor, attached to top of com pressor
cylinder head, controls com pression of air. C rankshaft is
m ounted in a ball bearing in front and insert type bearing
at the rear. C onnecting rod bearings are replaceable insert
TROUBLESHOOTING CHART
This Troubleshooting C h art is to serve as a guide to fa­
cilitate an accurate diagnosis of a
pressor and governor.
m alfunctioning air com-
COMPRESSOR FAILS TO MAINTAIN
SUFFICIENT PRESSURE
COMPRESSOR PASSES EXCESSIVE OIL
Excessive wear.
Dirty intake strainer. Dirty air strainer, (Im proper air strainer
Restriction in com pressor cylinder head intake maintenance.)
or discharge cavities or in discharge line. High inlet vacuum .
Leaking or broken discharge valves. Small oil return line.
Excessive wear. Excessive oil pressure.
Drive belt slipping.
Oil supply or return lines to com pressor
Inlet valves stuck open. flooded.
W orn inlet valves.
Defective or worn oil seal rings in end cover.
Excessive system leakage or usage. Piston rings not properly installed.
Back pressure from engine crankcase.
NOISY OPERATION COMPRESSOR NOT UNLOADING
Loose drive pulley.
Defective inlet valve plunger or spring.
Restrictions in cylinder head or discharge line. Intake cavity restrictions.
W orn or burned out bearings.
Defective governor.
C om pressor not getting proper lubrication.
U nloader line or cavity to governor restricted.
Excessive wear.
U nloader m echanism binding or stuck.
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SH O P M A N U A L