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ENGINE COOLING
6B-11
checked, swollen or otherwise deteriorated. Every two years
or 30,000 miles, whichever first occurs, the cooling system
should be flushed and refilled using the following
recommended procedure:
1. Remove radiator cap when engine is cool by:
Slowly rotating cap counterclockwise to detent. (Do
not press down while rotating).
Wait until any residual pressure (indicated by a hissing
sound) is relieved.
After all hissing ceases, press down on cap while
continuing to rotate counterclockwise.
C A U T I 0 N
:
To a void the danger o f being burned,
do not remove radiator cap while engine and
radiator are still hot because scalding fluid and
steam will be blown out under pressure.
2. Open radiator drain valve and block drain plugs to
drain coolant.
3. Close valve, install block drain plugs, and add
sufficient water to fill system.
4. Run engine, drain and refill the system, as described
in steps 1, 2, 3 and 4, a sufficient number of times until the
drained liquid is nearly colorless.
5. Allow system to drain completely and then close
radiator drain valve tightly, and install block drain plugs.
6. Remove recovery cap leaving hoses in place. Remove
coolant recovery tank and empty of fluid. Flush tank with
clean water, drain and reinstall.
7. Add sufficient ethylene glycol coolant, meeting GM
specification, 1799-M, to provide the required freezing and
corrosion protection
-
at least 44 percent solution (20°F. [-
29"C.l). Fill radiator to the base of the radiator fill neck and
add sufficient coolant to the recovery tank to raise level to
the "FULLVmark. Reinstall recovery tank cap.
8. Run engine, with radiator cap removed, until normal
operating temperature is reached. (Radiator upper hose
becomes hot).
9. With engine idling, add coolant until level reaches
bottom of filler neck and install radiator cap making certain
arrows line up with overflow tube.
It is the owner's responsibility to keep the freeze
protection at a level commensurate with the temperatures
which may occur in the area of vehicle operation. Maintain
cooling system freeze protection at -20°F. (-29°C.) or below
to ensure protection against corrosion and loss of coolant
from boiling even though freezing temperatures are not
expected. Add ethylene glycol base coolant that meets GM
Specification 1899-M when coolant additions are required
because of coolant loss or to provide additional protection
against freezing at temperatures lower than -20°F. (-29°C.)
(-35°F. [-38"C.l in Canada).
NOTE: Alcohol or methanol base coolants or plain
water are not recommended at any time.
TESTING COOLANT
Two recommended methods of testing coolant are
available, the hydrometer test and the refractometer test (J-
23688): 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
'emperature correction, test should be made at temperature
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. [17"C.]). 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
hydrometer should be closely followed as large differences in
readings can occur due to temperature calibration.
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. 6B- 12).
Fig.
68-1
2 Cleaning Refractometer
TEST1 NG
Fig.
68-1
3 Procedure for Collecting Coolant Sample
Do not remove clear plastic pump from Tester. Release
tip of pump from Tester housing and insert into radiator filler
neck. Be sure to insert well below level of fluid. Press and
release bulb to draw up a sample of coolant (Fig. 6B- 13).
Bend plastic tube around Tester so that tip can be inserted
in cover plate opening. Eject a few drops of coolant into
measuring surface by pressing bulb (Fig. 6B-13).
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