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7 - 18
COOLING SYSTEM
DIAGNOSIS AND TESTING (Continued)
For wiring diagrams of the fan motor systems refer
to Group, 8W Wiring Diagrams.
COOLANT CONCENTRATION TESTING
Coolant concentration should be checked when any
additional coolant was added to system or after a
coolant drain, flush and refill. The coolant mixture
offers optimum engine cooling and protection against
corrosion when mixed to a freeze point of -37°C
(-34°F) to -59°C (-50°F). The use of a hydrometer or a
refractometer can be used to test coolant concentra-
tion.
Hydrometers test the amount of glycol in a mixture
by measuring the specific gravity of the mixture. The
higher the concentration of ethylene glycol, the larger
the number of balls that will float, and higher the
freeze protection (up to a maximum of 70% by vol-
ume glycol).
Refractometers test the amount of glycol in a cool-
ant mixture by measuring the amount a beam of
light bends as it passes through the fluid.
Some coolant manufactures use other types of gly-
cols into their coolant formulations. Propylene glycol
is the most common new coolant. However, propylene
glycol based coolants do not provide the same freez-
ing protection and corrosion protection and is only
recommended for limited usage. Refer to appropriate
Technical Service Bulletin(s) regarding use of propy-
lene glycol based coolants.
CAUTION: Do not mix types of coolant—corrosion
protection will be severely reduced.
Because ethylene glycol and propylene glycol do
not have the same specific gravities, the use of a
hydrometer will be inaccurate. Therefore, Special
Tool 8286 refractometer, must be used when testing
coolant.
NOTE: A refractometer should be used if the glycol
type is unknown, and to achieve an accurate read-
ing of freeze protection.
TESTING SYSTEM FOR LEAKS
With engine not running, wipe the coolant filler
neck sealing seat clean. The radiator should be full.
Attach a radiator pressure tester to the coolant
filler neck, as shown in (Fig. 23) and apply 104 kPa
(15 psi) pressure. If the pressure drops more than 2
psi in 2 minutes inspect all points for external leaks.
All hoses, radiator and heater, should be moved
while at 104 kPa (15 psi) since some leaks occur
while driving due to engine rock, etc.
If there are no external leaks after the gauge dial
shows a drop in pressure, detach the tester. Start
engine and run the engine to normal operating tem-
Fig. 23 Pressure Testing Cooling System—Typical
perature in order to open the thermostat and allow
the coolant to expand. Reattach the tester. If the nee-
dle on the dial fluctuates, it indicates a combustion
leak and is usually a head gasket leak.
WARNING: WITH
TOOL
BUILDS UP FAST. ANY EXCESSIVE AMOUNT OF
PRESSURE BUILT UP BY CONTINUOUS ENGINE
OPERATION MUST BE RELEASED TO A SAFE
PRESSURE POINT. NEVER PERMIT PRESSURE TO
EXCEED 138 kPa (20 psi).
If the needle on the dial does not fluctuate, race
the engine a few times. If an abnormal amount of
coolant or steam is emitted from the tailpipe, it may
indicate a faulty head gasket, cracked engine block or
cylinder head.
There may be internal leaks which can be deter-
mined by removing the oil dipstick. If water globules
appear intermixed with the oil, it will indicate a
internal leak in the engine. If there is an internal
leak, the engine must be disassembled for repair.
PRESSURE CAP TO FILLER NECK SEAL
PRESSURE RELIEF CHECK
The pressure cap upper gasket (seal) pressure relief can
be checked by removing the overflow hose at the radiator
filler neck nipple (Fig. 24). Attach the radiator pressure
tester to the filler neck nipple, and pump air into the
system. The pressure cap upper gasket should relieve
pressure at 69-124 kPa (10-18 psi), and hold pressure
at 55 kPa (8 psi) minimum.
WARNING: THE WARNING WORDS DO NOT OPEN
HOT ON THE PRESSURE CAP IS A SAFETY PRE-
CAUTION. WHEN HOT, THE COOLING SYSTEM
BUILDS UP PRESSURE. TO PREVENT SCALDING
OR OTHER INJURY, THE PRESSURE CAP SHOULD
NOT BE REMOVED WHILE THE SYSTEM IS HOT
AND/OR UNDER PRESSURE.
JA
IN
PLACE
PRESSURE
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