Pontiac FIREBIRD 1972 Service Manual page 632

6A- 12
1972 PONTIAC SERVICE MANUAL
NOTE: To remove cap completely, turn coun-
terclockwise to first detent, push down and
continue rotation until removed.
To assure most effective heater performance, all models.
are equipped with a 195°F. thermostat.
Non-glycol base coolant should not be used.
TESTING COOLANT
Two recommended methods of testing coolant are availa-
ble, the hydrometer test and the refractometer test (J-
23688):
HYDROMETER TEST
In using a hydrometer to determine the freezing point of
radiator solution, make sure correct hydrometer markings
are read. Unless hydrometer is provided with means for
temperature correction, test should be made at tempera-
ture at which hydrometer is calibrated, for if the solution
is warmer or colder, large errors may result (in some cases
as much as 30°F). Most good hydrometers are equipped
with a thermometer and temperature correction scale
which allows an accurate test of freezing point over a
range of temperatures.
The manufacturer's instructions on use of their hydrome-
ter should be closely followed as large differences in read-
ings can occur due to temperature calibration.
Fig. 6 A - 1 5 Procedure for Collecting Coolant Sample
REFRACTOMETER TEST
CLEANING
Before each use, swing back the plastic cover at the
slanted end of the Tester, exposing both the measuring
window and the bottom of the plastic cover. WIPE BOTH
CLEAN AND DRY with tissue or clean soft cloth. Close
the plastic cover (Fig. 6A-14).
Fig. 6A-14 Cleaning Refractometer
Fig. 6A-16 Reading Refractometer