Pontiac FIREBIRD 1972 Service Manual page 625

ENGINE COOLING AND LUBRICATION 6A-5
NOTE: J 6742-01 reads to 180 degrees F, there-
fore, aflo w approximately 3/16" pointer move-
ment for each 10 degrees over 180 degrees.
Position thermometer so that the thermomoeter
sensor is centered in the space between the fan
blades and radiator. This can be achieved by in-
serting the sensor through one of the existing
holes in the fan shroud or fan guard, or by placing
between the radiator and the shroud. On some
models, it may be necessary to drill a 3/16" hole
in the fan shroud to insert J 6742-01.
CAUTION: Check for adequate clearance be-
tween fan blades and thennometer sensor
before starting engine.
d. Cover radiator grille sufficiently to induce a high
engine temperature. Start engine and turn on
A/C if equipped. Maintain a position in front of
the vehicle to observe the thermometer reading
while engine is running at approximately 2000
r.p.m. Use tachometer if available.
e. Observe thermometer reading when clutch en-
gages. It will take approximately 5 to 10 minutes
for the temperature to become high enough to
ENGINE COOLING SYSTEM
allow engagement of the fan clutch. This will be
indicated by an increase or roar in fan air noise
and by a drop in the thermometer reading of
approximattely 5- 15 degrees F. If the clutch did
not engage between 150-190 degrees F, the unit
should be replaced.
NOTE: Be sure fan clutch was disengaged at
beginning of test.
If no sharp increase in fan noise or temperature drop
was observed and the fan noise level was con-
stantly high from start of test to 190 degrees F,
the unit should be replaced.
CAUTION: Do not continue test past a ther-
mometer reading of 190 degrees F to prevent
engine overheating.
I
f. As soon as the clutch engages, remove the radia-
tor grille cover and turn off the A/C to assist in
engine cooling. The engine should be run at ap-
proximately 1500 r.p.m.
g. After several minutes the fan clutch should disen-
gage, as indicated by a reduction in fan speed and
roar.
GENERAL DESCRIPTION
The cooling system consists of the radiator cap, radiator,
hoses, water pump, cooling fan, pellet-type thermostat
and suitable passages for water circulation through the
engine.
RADIATOR
A cross-flow radiator is used on all models. Tanks in this
type radiator are located to the right and left of the core,
instead of above and below (Fig. 6A-5).
Radiators used with automatic transmissions have oil
coolers built into the right hand tank with inlet and outlet
fittings for transmission fluid circulation.
Synchromesh-equipped cars utilized radiators without oil
coolers.
Vehicles equipped with air conditioning use a radiator
with extra cooling capacity for greater cooling demands.
A drain cock is located at the inside lower left hand corner
of the radiator.
RADIATOR CAP
A pressure-vent cap is used on the cross-flow radiator to
allow a build-up of 15 psi in the cooling system. This
pressure raises the boiling point of coolant to approxi-
mately 258°F. at sea level.
CAUTION: As long as there is pressure in the
cooling system, the temperature can be consid-
erably higher than the boiling temperature of
the solution in the radiator without causing the
solution to boil. Removal of the radiator cap
while engine is hot and pressure is high will
cause the solution to boil instantaneously and
possibly with explosive force, spewing the solu-
tion over engine, fenders and person removing
cap. I f the solution contains flammable anti-
freeze such as alcohol (not recommended for
use at any time), there is also the possibi/ity of
causing a serious fie. When removing filler
cap, rotate cap toward left very slowly. I f hiss-
ing o f vapor is encountered, tighten cap im-
mediately and wait for system to cool
sufficiently to allow removal of cap. A fterpres-
sure in system has been relieved, turn cap coun-
terclockwise to fist detent, push down and
continue rotating counterclock wise until cap
can be removed. Turn cap all the way to right