Pontiac FIREBIRD 1972 Service Manual page 631

ENGINE COOLING AND LUBRICATION 6A-11
water will always recirculate as outlined above. A major
portion of the water, however, will circulate into a pass-
ange in the intake manifold as above but will then pass
directly into the radiator, via the outlet passage and hose
above the thermostat, and then back to the pump inlet.
The water pump and water transfer holes between the
block and cylinder heads have been designed to provide an
equitable flow of coolant and provide temperature balance
in both banks of the engine and within each bank and its
cylinder head.
ber one cylinder (Fig. 6A-4). Coolant then flows through
the block toward the rear, passing through two large cast
openings into the cylinder head to cool the valve seats and
forward to the front of the head. Coolant then flows
through the coolant outlet and the pellet-type thermostat
to the radiator. Some coolant is directed through a small
hole in the cylinder head gasket to an area around each
spark plug.
During engine warm-up when the thermostat is closed,
water is redirected to the engine.
6 CYLINDER
The water pump discharges coolant into the water jacket
chamber between the front face of the block and the num-
SERVICE OPERATIONS
COOLING SYSTEM
CHECKING AND FILLING
hoses removed) as any reverse flushing of the block
with the water pump in place may cause the water
pump seal to leak if flushing pressure is excessive.
The cooling system requires little care except for main-
taining an adequate coolant level. If GM glycol-type in-
hibited engine coolant is used, it is not necessary to drain PREPARING COOLING SYSTEM FOR COOLANT
the coolant for summer driving because this coolant has
been especially formulated to last 24 months in the cooling
The cooling system should be properly prepared for the
system. After service for 24 months, drain the system,
addition of coolant every two years.
flush it with water and refill with an inhibited year-round
coolant, meeting the GM 1899M specification.
To properly prepare cooling system:
1. Bring engine up to operating temperature.
FLUSHING
1. Drain radiator and block by opening drain plug on
radiator left tank and removing plug on left side of 6
cylinder engine block and on both sides of 8 cylinder
engine block.
2. After system is empty, with drains open, run water
into radiator. Engine should be running and occa-
sionally accelerated to aid in circulating water and to
dislodge rust and scale.
CAUTION: Do not introduce cold water into a
hot engine or the block may be cracked. A flu w
engine to coo/, then add water with engine run-
ning.
3. Where there is difficulty in getting water to run clear
or there is an excessive amount of rust and scale, the
cooling system should be cleaned with a cleanser
(reputable source) supplied for that purpose. If force-
flushing equipment is used, it should be used on the
radiator only (engine to radiator inlet and outlet
2. Flush out cooling system, as indicated previously.
3. Tighten all hose connections on radiator, engine,
heater and defroster. Replace any deteriorated hose.
Check to see that radiator hold-down bolts are tight-
ened properly.
4. Fill system with water and operate engine, checking
for water leaks at radiator core, hose connections,
water pump seal and gaskets, heater and defroster
connections and head to block joint.
5. Drain sufficient water to allow addition of proper
quantity of coolant.
Do not overfill. Coolant should be 1" below filler neck
opening with hot engine, 3" below filler neck with
cold engine for all models.
CAUTION:
A
pressure radiator cap is used to
provide the best cooling. When removing, ro-
tate cap to left very slowly. If hissing noise is
heard, stop and allow pressure to decrease
before removing cap completely.