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1C-14 COOLING SYSTEMS
Fig. 1C-12 Disconnecting Tempatrol Spring Coll
Gap between end of coil and clip on housing should be
approximately 1/2 inch (13 mm). Replace unit if shaft
does not rotate with coil. After test, connect end of coil
in slot.
Dynamic Test
CAUTION: Ensure there is adequate fan blade clear
ance before drilling.
(1) Drill 1/8-inch (3.18-mm) diameter hole in top
center of shroud.
CAUTION: Ensure there is adequate clearance from
fan blades.
(2) Insert dial thermometer (0° to 220°F [-18° to
105°C]) with 8-inch stem, or equivalent, through hole in
shroud.
(3) Connect tachometer and engine ignition timing
light (to be used as strobe light). Refer to Chapter 1A for
procedures.
(4) Block airflow through radiator by securing
sheet of plastic in front of radiator (or air conditioning
condenser). Tape shut at top to secure plastic and ensure
airflow is blocked.
NOTE: Ensure air conditioner, if equipped, is turned
off
WARNING: Use extreme caution when engine is oper
ating. Do not stand in direct line with fan. Do not put
hands near pulleys, belts or fan. Do not wear loose
clothing.
(5) Start engine and operate at 2400 rpm with tim
ing light aimed at fan blades (strobe light).
(6) Within ten minutes air temperature (indicated
on dial thermometer) should be 190°F (88°C). Satisfac
tory operation of fan drive requires that it engage before
or at 190°F (88°C). Engagement is distinguishable by
definite increase in audible fan airflow noise. Timing
light will also indicate increase in speed of fan.
(7) When air temperature reaches 190°F (88°C), re
move plastic sheet. Satisfactory operation of Tempatrol
fan requires air temperature to drop 20°F (11°C) or
more. Definite decrease of audible fan airflow noise
should be noticed. Replace defective fan assemblies.
NOTE: The cooling system must be in good condition
prior to performing the test outlined above to ensure
against excessively high coolant temperature.
FAN SHROUD
In some extreme situations, the engine fan blades may
contact the shroud. An examination for proper engine
mounting should isolate the problem. If not, examine
the shroud position. To compensate for normal engine
movement, loosen the shroud attaching screws and repo
sition shroud to prevent fan-to-shroud contact. Inspect
the fan for bent blades and replace fan if necessary.
COOLANT RECOVERY SYSTEM
The coolant recovery system consists of a special
pressure radiator cap, an overflow tube and a plastic
coolant recovery bottle (fig. 1C-13). Refer to the Cooling
System Components chart for specific applications.
The radiator cap used with the recovery system has a
gasket to prevent air leakage at the filler neck. The cap
has very short finger grips (to discourage unnecessary
removal) and has a mark on top that aligns with the
overflow tube to indicate the proper installed position.
The overflow tube fits into the top of the plastic bottle
and extends to the bottom. The overflow tube must
always be submerged in coolant.
Coolant Recovery Operation
As engine temperature increases, the coolant expands.
The radiator cap pressure vent valve (normally open)
slowly allows transfer of expanding coolant to the cool
ant recovery bottle. Any air trapped in the system will
also be expelled during this period.
If ambient temperature is high, the system continues
heating until vapor bubbles form. These vapor bubbles
pass rapidly through the radiator cap vent valve, caus
ing it to close. Further expansion of the coolant pressur
izes the system up to 14 psi (96.5 kPa). Above 14 psi (96.5
kPa) the relief valve in the cap allows pressurized cool
ant to escape to the coolant recovery system.
As engine temperature drops, the coolant loses heat
and contracts, forming a partial vacuum in the system.
The radiator cap vacuum valve then opens and allows
atmospheric pressure to force coolant from the recovery
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Troubleshooting
