Jeep 1997 Grand Cherokee Service Manual page 245

ZG
DIAGNOSIS AND TESTING (Continued)
CONDITION
HEAT ODOR
POOR DRIVEABILITY (THERMOSTAT
POSSIBLY STUCK OPEN). GAUGE MAY BE
READING LOW
STEAM IS COMING FROM FRONT OF
VEHICLE NEAR GRILL AREA WHEN
WEATHER IS WET, ENGINE IS WARMED
UP AND RUNNING, AND VEHICLE IS
STATIONARY. TEMPERATURE GAUGE IS
IN NORMAL RANGE
COOLANT COLOR
COOLANT LEVEL CHANGES IN COOLANT
RESERVE/OVERFLOW TANK.
TEMPERATURE GAUGE IS IN NORMAL
RANGE
POSSIBLE CAUSES
1. Various heat shields are used at certain
drive line components. One or more of these
shields may be missing.
2. Is temperature gauge reading above the
normal range?
3. Is cooling fan operating correctly.
4. Has undercoating been applied to any
unnecessary component.
5. Engine may be running rich causing the
catalytic converter to overheat.
1. For proper driveability, good vehicle
emissions and for preventing build-up of
engine oil sludge, the thermostat must be
operating properly. Has a diagnostic trouble
code (DTC) number 17 been set?
1. During wet weather, moisture (snow, ice
or rain condensation) on the radiator will
evaporate when the thermostat opens. This
opening allows heated water into the
radiator. When the moisture contacts the hot
radiator, steam may be emitted. This usually
occurs in cold weather with no fan or airflow
to blow it away.
1. Coolant color is not necessarily an
indication of adequate corrosion or
temperature protection. Do not rely on
coolant color for determining condition of
coolant.
1. Level changes are to be expected as
coolant volume fluctuates with engine
temperature. If the level in the tank was
between the FULL and ADD marks at normal
engine operating temperature, the level
should return to within that range after
operation at elevated temperatures.
COOLING SYSTEM
CORRECTION
1. Locate missing shields and replace or
repair as necessary.
2. Refer to the previous Temperature Gauge
Reads High in these Diagnosis Charts.
Repair as necessary.
3. Refer to Cooling System Fan in this group
for diagnosis. Repair as necessary
4. Clean undercoating as necessary.
5. Refer to the DRB scan tool and the
appropriate Powertrain Diagnostic
Procedures service manual. Repair as
necessary.
1. Refer to On-Board Diagnostics in this
group. DTC's may also be checked using the
DRB scan tool. Refer to the proper
Powertrain Diagnostics Procedures service
manual for checking the thermostat using the
DRB scan tool. Replace thermostat if
necessary.
1. Occasional steam emitting from this area
is normal. No repair is necessary.
1. Refer to Coolant in this group for
antifreeze tests. Adjust antifreeze-to-water
ratio as necessary.
1. A normal condition. No repair is necessary.
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