Pontiac tempest 1968 Service Manual page 298

6A-1
ENGINE COOLING AND LUBRICATION
CONTENTS OF THIS SECTION
SUBJECT PAGE
Cooling System Description . . . . . . . . . 6A-1
Radiator and Cap 6A-1
Water Pump. 6A-2
Fan 6A-2
Service Operations 6A-2
Thermostat 6A-3
SUBJECT PAGE
Water Pump . 6A-3
Radiator. 6 A-3
Oil Filter . 6A-5
Drive Belt Chart 6A-7
Torque Specifications 6A-8
Service Specifications 6A-8
GENERAL DESCRIPTION
ENGINE COOLING SYSTEM
The cooling system consists of the radiator, cap,
radiator hoses, water pump, cooling fan, pellet-type
thermostat and suitable passages for water circula­
tion through the engine.
RADIATOR—ALL MODELS
A cross-flow radiator is used on all 1968 Pontiacs
instead of the conventional down-flow type
0
The
cross-flow radiator differs in the fact that water
flows horizontally and the tanks are on the left and
right side of the core instead of above and below the
core.
The cross-flow radiator offers improved cooling
capabilities while making possible a lower front end
silhouette due to its reduced height. The low, wide
shape of the cross-flow radiator matches the grille
opening more efficiently, providing greater radiator
exposure and more effective cooling surface.
Radiators used with automatic transmission have
oil coolers built into the right tank with inlet and
outlet fittings for circulation of transmission fluid.
The Pontiac radiator used with automatic transmis­
sion is equipped with heavy duty oil cooler when
used on police cars, trailer options, etc., and as
optional equipment where extreme cooling conditions
must be met.
The radiator used with the synchromesh trans­
mission is a cross-flow without oil cooler. Cars
equipped with air conditioning and performance op­
tions use a radiator which has more cooling capacity
for greater cooling demands.
A drain cock is located at inside lower left corner
of radiator.
RADIATOR CAP
A pressure-vent cap is used on the radiator to
allow a build-up of 15 psi of pressure in the cooling
system. This pressure raises the boiling point of
coolant to approximately 258°F. at sea level.
CA UTION: As long as there is pressure in the
cooling system, the temperature can be consider­
ably higher than the boiling temperature of the
solution in 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 solution over engine, fenders,
and person removing cap. If the solution contains
inflammable anti-freeze, such as alcohol, there is
also the possibility of causing a serious fire. When
removing filler cap, rotate cap toward left very
slowly; if hissing of vapor is encountered, tighten
cap immediately and wait for system to cool suf­
ficiently to allow removal of cap. After pressure
in system has been relieved, turn cap more
forcibly to left and remove. Turn cap all the way
to right when installing. It should not be necessary
to check coolant level unless temperature gauge
shows over-heating, and then not until engine is
stopped and allowed to cool to normal.
The pressure type radiator filler cap contains a
blow off or pressure valve and a vacuum or atmos­
pheric valve. The pressure valve is held against its
seat by a spring of pre-determined strength which
protects the radiator by relieving the pressure if an
extreme case of internal pressure should exceed that
for which the cooling system is designed. The vacu­
um valve is held against its seat by a light spring
which permits opening of the valve to relieve vacuum
created in the system when it cools off and which
otherwise might cause the radiator to collapse.