Cooling System - Jeep 1997 Grand Cherokee Service Manual

7 - 14

COOLING SYSTEM

DIAGNOSIS AND TESTING (Continued)
COOLING SYSTEM DIAGNOSIS
CONDITION
TEMPERATURE GAUGE READS LOW
TEMPERATURE GAUGE READS HIGH OR
ENGINE COOLANT WARNING LAMP
ILLUMINATES. COOLANT MAY OR MAY
NOT BE LOST OR LEAKING FROM
COOLING SYSTEM
POSSIBLE CAUSES
1. Has a Diagnostic Trouble Code (DTC)
number 17 been set indicating a stuck open
engine thermostat.
2. Is the temperature gauge (if equipped)
connected to the temperature gauge coolant
sensor on the engine?
3. Is the temperature gauge (if equipped)
operating OK?
4. Coolant level low in cold ambient
temperatures accompanied with poor heater
performance.
5. Improper operation of internal heater
doors or heater controls.
1. Trailer is being towed, a steep hill is being
climbed, vehicle is operated in slow moving
traffic, or engine is being idled with very high
ambient (outside) temperatures and the air
conditioning is on. Higher altitudes could
aggravate these conditions.
2. Is temperature gauge (if equipped)
reading correctly?
3. Is temperature warning lamp (if equipped)
illuminating unnecessarily?
4. Coolant low in coolant reserve/overflow
tank and radiator?
5. Pressure cap not installed tightly. If cap is
loose, boiling point of coolant will be
lowered. Also refer to the following step 6.
6. Poor seals at radiator cap.
7. Coolant level low in radiator but not in
coolant reserve/overflow tank. This means
the radiator is not drawing coolant from the
coolant reserve/overflow tank as the engine
cools.
As the engine cools, a vacuum is formed in
the cooling system of the engine and
radiator. If radiator cap seals are defective,
or cooling system has leaks, a vacuum can
not be formed.
8. Freeze point of antifreeze not correct.
Mixture may be too rich.
CORRECTION
1. Refer to On-Board Diagnostics in the
service manual text. Replace thermostat if
necessary. If a Diagnostic Trouble Code
(DTC) number 17 has not been set, the
problem may be with the temperature gauge.
2. Check the engine temperature sensor
connector in the engine compartment. Refer
to Group 8E. Repair as necessary.
3. Check gauge operation. Refer to Group
8E. Repair as necessary.
4. Check coolant level in the coolant
reserve/overflow tank and the radiator.
Inspect system for leaks. Repair leaks as
necessary. Refer to the Coolant section of
the manual text for Warnings and precautions
before removing the radiator cap.
5. Inspect heater and repair as necessary.
Refer to Group 24, Heating and Air
Conditioning for procedures.
1. This may be a temporary condition and
repair is not necessary. Turn off the air
conditioning and attempt to drive the vehicle
without any of the previous conditions.
Observe the temperature gauge. The gauge
should return to the normal range. If the
gauge does not return to normal range,
determine the cause for overheating and
repair. Refer to POSSIBLE CAUSES
(numbers 2 through 18).
2. Check gauge. Refer to Group 8E. Repair
as necessary.
3. Check warning lamp operation. Refer to
Group 8E. Repair as necessary.
4. Check for coolant leaks and repair as
necessary. Refer to Testing Cooling System
for Leaks in this group.
5. Tighten cap.
6. (a) Check condition of cap and cap seals.
Refer to Radiator Cap. Replace cap if
necessary.
(b) Check condition of radiator filler neck. If
neck is bent or damaged, replace radiator.
7. (a) Check condition of radiator cap and
cap seals. Refer to Radiator Cap in this
group. Replace cap if necessary.
(b) Check condition of radiator filler neck. If
neck is bent or damaged, replace radiator.
(c) Check the condition of the hose from the
radiator to the coolant tank. It should fit tight
at both ends without any kinks or tears.
Replace hose if necessary.
(d) Check coolant reserve/overflow tank and
tank hoses for blockage. Repair as
necessary
8. Check antifreeze. Refer to Coolant section
of this group. Adjust antifreeze-to-water ratio
as required.
ZG