Ordinary worm gear type hose clamps (when
equipped) can be removed with a straight screw-
driver or a hex socket. To prevent damage to
hoses or clamps, the hose clamps should be
tightened to 4 N·m (34 in. lbs.) torque. Do not
over tighten hose clamps.
When performing a hose inspection, inspect the
radiator lower hose for proper position and condition
of the internal spring.
VISCOUS FAN DRIVE
The thermal viscous fan drive (Fig. 6) is a silicone-
fluid-filled coupling. It connects the fan blade assem-
bly to the fan pulley. The coupling allows the fan to
be driven in a normal manner. This is done at low
engine speeds while limiting the top speed of the fan
to a predetermined maximum level at higher engine
speeds. A bimetallic spring coil is located on the front
face. This spring coil reacts to the temperature of the
radiator discharge air. It engages the viscous fan
drive for higher fan speed if the air temperature from
the radiator rises above a certain point. Until addi-
tional engine cooling is necessary, the fan will remain
at a reduced rpm regardless of engine speed.
The viscous fan drive will only engage when suffi-
cient heat is present. This is when the air flowing
through the radiator core causes a reaction from the
bimetallic coil. It then increases fan speed to provide
the necessary additional engine cooling.
Once the engine has cooled, the radiator discharge
temperature will drop. The bimetallic coil again
reacts and the fan speed is reduced to the previous
disengaged speed.
CAUTION: Some engines equipped with serpentine
drive belts have reverse rotating fans and viscous
fan
drives.
They
are
marked
with
the
word
REVERSE to designate their usage. Installation of
the wrong fan or viscous fan drive can result in
engine overheating.
NOISE
NOTE: It is normal for fan noise to be louder (roar-
ing) when:
•
The underhood temperature is above the engage-
ment point for the viscous drive coupling. This may
occur when ambient (outside air temperature) is very
high.
•
Engine loads and temperatures are high such as
when towing a trailer.
•
Cool silicone fluid within the fan drive unit is
being redistributed back to its normal disengaged
(warm) position. This can occur during the first 15
seconds to one minute after engine start-up on a cold
engine.
LEAKS
Viscous fan drive operation is not affected by small
oil stains near the drive bearing. If leakage appears
excessive, replace the fan drive unit.
BELT TENSION
Correct accessory drive belt tension is required to
be sure of optimum performance of belt driven engine
accessories. If specified tension is not maintained,
belt slippage may cause; engine overheating, lack of
power steering assist, loss of air conditioning capac-
ity,
reduced
generator
output
rate
and
greatly
reduced belt life.
Initial belt adjustment is done with a adjustable
tensioner pulley. After the initial adjustment is per-
formed, an automatic belt tensioner is used to main-
tain correct belt tension at all times. Do not attempt
to check belt tension with a belt tension gauge on
vehicles equipped with an automatic belt tensioner.
Refer to Automatic Belt Tensioner in this group.
Fig. 6 Viscous Fan Drive
7 - 6
COOLING SYSTEM
ZG
DESCRIPTION AND OPERATION (Continued)
Summary of Contents for 1997 Grand Cherokee
Page 6: ...FASTENER IDENTIFICATION 4 INTRODUCTION ZG GENERAL INFORMATION Continued ...
Page 9: ...METRIC CONVERSION ZG INTRODUCTION 7 GENERAL INFORMATION Continued ...
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Page 285: ...ZG COOLING SYSTEM 7 11 DIAGNOSIS AND TESTING Continued ...
Page 286: ...7 12 COOLING SYSTEM ZG DIAGNOSIS AND TESTING Continued ...
Page 290: ...SERPENTINE DRIVE BELT DIAGNOSIS 7 16 COOLING SYSTEM ZG DIAGNOSIS AND TESTING Continued ...
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Page 423: ...VIC Initial Set Up ZG INSTRUMENT PANEL SYSTEMS 8E 21 SERVICE PROCEDURES Continued ...
Page 424: ...VIC Reset 8E 22 INSTRUMENT PANEL SYSTEMS ZG SERVICE PROCEDURES Continued ...
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Page 1655: ...Fig 3 Oil Lubrication System ZG 5 2L ENGINE 9 57 DESCRIPTION AND OPERATION Continued ...
Page 1684: ...TORQUE 9 86 5 2L ENGINE ZG SPECIFICATIONS Continued ...
Page 1689: ...Fig 3 Oil Lubrication System ZG 5 9L ENGINE 9 91 DESCRIPTION AND OPERATION Continued ...
Page 1723: ...DIAGNOSIS AND TESTING SERVICE DIAGNOSIS DIESEL PERFORMANCE ZG ENGINE 9 3 ...
Page 1724: ...9 4 ENGINE ZG DIAGNOSIS AND TESTING Continued ...
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Page 2122: ...DIAGNOSIS AND TESTING NV231 DIAGNOSIS 21 8 TRANSMISSION AND TRANSFER CASE ZG ...