Jeep cherokee 2000 Service Manual page 257

XJ
DIAGNOSIS AND TESTING (Continued)
CONDITION
TEMPERATURE GAUGE READING
IS INCONSISTENT (FLUCTUATES,
CYCLES OR IS ERRATIC)
(CONTINUED)
PRESSURE CAP IS BLOWING
OFF STEAM AND/OR COOLANT
TO COOLANT TANK.
TEMPERATURE GAUGE READING
MAY BE ABOVE NORMAL BUT
NOT HIGH. COOLANT LEVEL MAY
BE HIGH IN COOLANT RESERVE/
OVERFLOW TANK
COOLANT LOSS TO THE
GROUND WITHOUT PRESSURE
CAP BLOWOFF. GAUGE READING
HIGH OR HOT
DETONATION OR PRE-IGNITION
(NOT CAUSED BY IGNITION
SYSTEM). GAUGE MAY OR MAY
NOT BE READING HIGH
HOSE OR HOSES COLLAPSE
WHILE ENGINE IS RUNNING
ELECTRIC RADIATOR FAN RUNS
ALL OF THE TIME (2.5L/4.0L
MODELS EQUIPPED WITH A/C
AND 4.0L MODELS EQUIPPED
WITH MAX COOLING)
POSSIBLE CAUSES
8. Water pump impeller loose on
shaft.
9. Loose accessory drive belt.
(water pump slipping)
10. Air leak on the suction side of
the water pump allows air to build
up in cooling system causing
thermostat to open late.
1. Pressure relief valve in radiator
cap is defective.
1. Coolant leaks in radiator, cooling
system hoses, water pump or
engine.
1. engine overheating.
2. Freeze point of coolant not
correct. Mixture is too rich or too
lean.
1. Vacuum created in cooling
system on engine cool-down is not
being relieved through coolant
reserve/overflow system.
1. Fan relay, powertrain control
module (PCM) or coolant
temperature sensor defective.
COOLING SYSTEM
CORRECTION
8. Check water pump and replace
as necessary. Refer to water Pumps
in this group.
9. Refer to Accessory Drive Belts in
this group. Check and correct as
necessary.
10. Locate leak and repair as
necessary.
1. Check condition of radiator cap
and cap seals. Refer to Radiator
Caps in this group. Replace cap as
necessary.
1. Pressure test and repair as
necessary. Refer to Cooling
System-Testing For Leaks in this
group.
1. Check reason for overheating
and repair as necessary.
2. Check coolant concentration.
Refer to the Coolant section of this
group and adjust ratio as required.
1. (a) Radiator cap relief valve
stuck. Refer to Radiator Cap in this
group. Replace if necessary
(b) Hose between coolant
reserve/overflow tank and radiator is
kinked. Repair as necessary.
(c) Vent at coolant reserve/overflow
tank is plugged. Clean vent and
repair as necessary.
(d) Reserve/overflow tank is
internally blocked or plugged. Check
for blockage and repair as
necessary.
1. Refer to Electric Cooling Fan
Diagnosis and Testing. Also refer to
Group 8W, Wiring Diagrams. Repair
as necessary.
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