Chevrolet 70 1969 Series, Shop Manual

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ENGINE C O O L IN G SYSTEM 6K-5
COLD WEATHER OPERATION
Water, with an inhibitor, can be safely used as
a cooling medium in climates where temperatures
do not reach below 32°F. In lower temperatures,
anti-freeze solutions must be used. Before install­
ing anti-freeze solution, cooling system should be
inspected and serviced for cold weather operation,
as previously described under "Cleaning System''
in this section.
Cylinder head bolts should be checked for
tightness and gasket replaced if necessary, to
avoid possibility of anti-freeze solution leaking
into engine, and exhaust gases entering cooling
system. If Ethylene Glycol anti-freeze is to be used
on vehicles having a water filter, the water filter
must be serviced at regular intervals as directed
later in this section under "Water Filter." After
anti-freeze solution has been installed, entire sys­
tem should be inspected regularly for leaks.
T H A W IN G C O O L IN G S Y S T E M
If cooling medium in system becomes frozen
solid, place vehicle in warm place until ice is
completely thawed out.
U N D E R N O C IR C U M ­
ST A N C E S S H O U L D E N G IN E BE R U N W H E N C O O L ­
ING S Y S T E M IS F R O Z E N S O LID.
The inhibited year-around (permanent-type)
engine coolant, used to fill the cooling system at
the factory is a high quality solution that meets
General Motors Specification 1899-M. This fac-
tory-fill coolant solution is formulated to with-
Water Manifold
A*____m..................................... .r .__
Figure
3
— Engine Units for Overheat Switch and
Temperature
Gauge
IV-6 Gasoline EngineI
stand two full calendar years of normal operation
without draining or adding inhibitors, and provides
freezing protection to -20° F.
It is the owner's responsibility to keep the
freeze protection at a level commensurate with
the area in which the vehicle will be operated.
Regardless of climate, system protection should
be maintained at least to 0 °F ., to provide adequate
corrosion protection. When adding solution due to
loss of coolant for any reason or in areas where
temperatures lower than -20° F., may occur, a suf­
ficient amount of an ethylene glycol base coolant
that meets G M Specification 1899-M should be used.
Every two years the cooling system should be
serviced by flushing with plain water, then com­
pletely refilling with a fresh solution of water and
a high-quality, inhibited (permanent type) glycol
base coolant meeting G M Specification 1899-M,
and providing freezing protection at least to read
0 °F . At this time, also add G M Cooling System
Inhibitor and Sealer or equivalent. In addition,
Cooling System Inhibitor and Sealer .should be add­
ed every fall thereafter. G M Cooling System In­
hibitor retards the formation of rust or scale and
is compatible with aluminum components.
N O T E : Alcohol or methanol base coolants or
plain water are not recommended for your truck
at any time.
WATER TEMPERATURE INDICATOR
Electric type temperature gauge system con­
sists of an engine thermal plug electrically con­
nected with registering gauge mounted on instru­
ment panel. Refer to applicable wiring diagram in
Section 12. System is activated when ignition is
turned on.
Engine unit is installed in engine water mani­
fold on V-6 gasoline engines (fig. 3) and in ther­
mostat housing on 6V-53 Diesel engines (fig. 2).
1. Disconnect wire at engine unit.
2. Connect a test light consisting of a 12-volt,
2-candlepower bulb and a pair of test leads in cir­
cuit by clipping one lead to battery positive term­
inal and other lead to body of engine gauge unit. If
bulb lights, unit is properly grounded. If bulb does
not light, check for presence of sealing compound
around threads of unit. Remove compound and re­
peat test. Make sure unit is properly grounded
before proceeding with next test.
3. Remove test lead from body of unit and
connect lead to terminal of unit. If bulb lights, en­
gine unit is internally short-circuited and should
be replaced.
4. Remove test light and reinstall wire on
unit.
CHEVROLET SERIES 70-80 H EAVY DUTY TRUCK SH O P M A N U A L