Jeep 200 Cherokee, Service Manual

Page: 296 / 2119

coil spring is located on the front face. This spring
coil reacts to the temperature of the radiator dis-
charge air. It engages the viscous fan drive for higher
fan speed if the air temperature from the radiator
rises above a certain point. Until additional 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
DESCRIPTION
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.
An automatic belt tensioner is used to maintain
correct belt tension at all times. Do not attempt to
check belt tension with a belt tension gauge on vehi-
cles equipped with an automatic belt tensioner.
AUTOMATIC BELT TENSIONER
DESCRIPTION
Drive belt tension is controlled by a spring loaded
automatic belt tensioner located below and to the
front of the engine oil filter (Fig. 9).
WARNING: BECAUSE OF HIGH SPRING PRES-
SURE, DO NOT ATTEMPT TO DISASSEMBLE THE
AUTOMATIC BELT TENSIONER. UNIT IS SERVICED
AS AN ASSEMBLY.
Fig. 9 Automatic Belt Tensioner Assembly
1 – FAN PULLEY
2 – IDLER PULLEY
3 – IDLER PULLEY
4 – GENERATOR
5 – POWER STEERING PUMP
6 – DRIVE BELT
7 – CRANKSHAFT PULLEY
8 – AUTOMATIC BELT TENSIONER
XJ
COOLING SYSTEM 7 - 7
DESCRIPTION AND OPERATION (Continued)