2002 JEEP LIBERTY check engine

CONDITION POSSIBLE CAUSES CORRECTION
15. Thermostat partially or
completely shut.15. Check thermostat operation and
replaces necessary. (Refer to 7 -
COOLING/ENGINE/ENGINE
COOLANT THERMOSTAT -
DIAGNOSIS AND TESTING).
16. Viscous fan drive not operating
properly.16. Check fan drive operation and
replace as necessary. (Refer to 7 -
COOLING/ENGINE/FAN DRIVE
VISCOUS CLUTCH - DIAGNOSIS
AND TESTING).
17. Cylinder head gasket leaking. 17. Check for cylinder head gasket
leaks. (Refer to 7 - COOLING -
DIAGNOSIS AND TESTING). For
repair, (Refer to 9 - ENGINE/
CYLINDER HEAD - REMOVAL).
18. Heater core leaking. 18. Check heater core for leaks.
(Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING/
HEATER CORE - REMOVAL).
Repair as necessary.
19. Electric fan not functioning. 19. Inspect electric fan for proper
operation. Refer to Electric Cooling
Fan in this section. Refer to Group
8W for electric cooling fan and relay
circuit schematic data.
TEMPERATURE GAUGE READING
IS INCONSISTENT (FLUCTUATES,
CYCLES OR IS ERRATIC)1. During cold weather operation,
with the heater blower in the high
position, the gauge reading may
drop slightly.1. A normal condition. No correction
is necessary.
2. Temperature gauge or engine
mounted gauge sensor defective or
shorted. Also, corroded or loose
wiring in this circuit.2. Check operation of gauge and
repair if necessary. Refer to Group
8J, Instrument cluster.
3. Gauge reading rises when
vehicle is brought to a stop after
heavy use (engine still running)3. A normal condition. No correction
is necessary. Gauge should return
to normal range after vehicle is
driven.
4. Gauge reading high after
re-starting a warmed up (hot)
engine.4. A normal condition. No correction
is necessary. The gauge should
return to normal range after a few
minutes of engine operation.
5. Coolant level low in cooling
system (air will build up in the
cooling system causing the
thermostat to open late).5. Check and correct coolant leaks.
(Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).
7 - 8 COOLINGKJ
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
6. Cylinder head gasket leaking
allowing exhaust gas to enter
cooling system causing a
thermostat to open late.6. (a) Check for cylinder head
gasket leaks. (Refer to 7 -
COOLING - DIAGNOSIS AND
TESTING).
(b) Check for coolant in the engine
oil. Inspect for white steam emitting
from the exhaust system. Repair as
necessary.
7. Water pump impeller loose on
shaft.7. Check water pump and replace
as necessary. (Refer to 7 -
COOLING/ENGINE/WATER PUMP -
DIAGNOSIS AND TESTING).
8. Loose accessory drive belt.
(water pump slipping)8. (Refer to 7 - COOLING/
ACCESSORY DRIVE/DRIVE BELTS
- DIAGNOSIS AND TESTING).
Check and correct as necessary.
9. Air leak on the suction side of
the water pump allows air to build
up in cooling system causing
thermostat to open late.9. Locate leak and repair as
necessary.
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 TANK1. Pressure relief valve in pressure
bottle cap is defective.1. Check condition of radiator cap
and cap seals. (Refer to 7 -
COOLING/ENGINE/RADIATOR
PRESSURE CAP - DIAGNOSIS
AND TESTING). Replace cap as
necessary.
COOLANT LOSS TO THE
GROUND WITHOUT PRESSURE
CAP BLOWOFF. GAUGE READING
HIGH OR HOT1. Coolant leaks in radiator, cooling
system hoses, water pump or
engine.1. Pressure test and repair as
necessary. (Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).
DETONATION OR PRE-IGNITION
(NOT CAUSED BY IGNITION
SYSTEM). GAUGE MAY OR MAY
NOT BE READING HIGH1. Engine overheating. 1. Check reason for overheating
and repair as necessary.
2. Freeze point of coolant not
correct. Mixture is too rich or too
lean.2. Check coolant concentration.
(Refer to 7 - COOLING/ENGINE/
COOLANT - DESCRIPTION) and
adjust ratio as required.
KJCOOLING 7 - 9
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
HOSE OR HOSES COLLAPSE
WHILE ENGINE IS RUNNING1. Vacuum created in cooling
system on engine cool-down is not
being relieved through coolant
reserve/overflow system.1. (a) Radiator cap relief valve
stuck. (Refer to 7 - COOLING/
ENGINE/RADIATOR PRESSURE
CAP - DIAGNOSIS AND TESTING).
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.
NOISY VISCOUS FAN/DRIVE 1. Fan blades loose - 4.0L. 1. Replace fan blade assembly.
(Refer to 7 - COOLING/ENGINE/
RADIATOR FAN - REMOVAL)
2. Fan blades striking a surrounding
object.2. Locate point of fan blade contact
and repair as necessary.
3. Air obstructions at radiator or air
conditioning condenser.3. Remove obstructions and/or
clean debris or insects from radiator
or A/C condenser.
4. Thermal viscous fan drive has
defective bearing - 4.0L4. Replace fan drive. Bearing is not
serviceable. (Refer to 7 - COOLING/
ENGINE/RADIATOR FAN -
REMOVAL).
INADEQUATE HEATER
PERFORMANCE. THERMOSTAT
FAILED IN OPEN POSITION1. Has a Diagnostic trouble Code
(DTC) been set?1. (Refer to 25 - EMISSIONS
CONTROL - DESCRIPTION) for
correct procedures and replace
thermostat if necessary
2. Coolant level low 2. (Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).
3. Obstructions in heater hose/
fittings3. Remove heater hoses at both
ends and check for obstructions
4. Heater hose kinked 4. Locate kinked area and repair as
necessary
5. Water pump is not pumping
water to/through the heater core.
When the engine is fully warmed
up, both heater hoses should be
hot to the touch. If only one of the
hoses is hot, the water pump may
not be operating correctly or the
heater core may be plugged.
Accessory drive belt may be
slipping causing poor water pump
operation.5. (Refer to 7 - COOLING/ENGINE/
WATER PUMP - DIAGNOSIS AND
TESTING). If a slipping belt is
detected, (Refer to 7 - COOLING/
ACCESSORY DRIVE/DRIVE BELTS
- REMOVAL). If heater core
obstruction is detected, (Refer to 7 -
COOLING - STANDARD
PROCEDURE) for cooling system
reverse flushing.
7 - 10 COOLINGKJ
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
STEAM IS COMING FROM THE
FRONT OF VEHICLE NEAR THE
GRILL AREA WHEN WEATHER IS
WET, ENGINE IS WARMED UP
AND RUNNING, AND VEHICLE IS
STATIONARY. TEMPERATURE
GAUGE IS IN NORMAL RANGE1. 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 or
condensor, steam may be emitted.
This usually occurs in cold weather
with no fan or airflow to blow it
away.1. Occasional steam emitting from
this area is normal. No repair is
necessary.
COOLANT COLOR 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. (Refer to 7 - COOLING/ENGINE/
COOLANT - DESCRIPTION) for
coolant concentration information.
Adjust coolant mixture as
necessary.
COOLANT LEVEL CHANGES IN
COOLANT RESERVE/OVERFLOW
TANK. TEMPERATURE GAUGE IS
IN NORMAL RANGE1. 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
operating temperature, the level
should return to within that range
after operation at elevated
temperatures.1. A normal condition. No repair is
necessary.
FAN RUNS ALL THE TIME 1. Fan control sensors inoperative. 1. Check for DTC's. Verify sensor
readings.
2. Fan control solenoid stuck9on9. 2. Check fan operation speeds.
Refer to fan speed operation table.
3. Fan control solenoid harness
damaged.3. Check for DTC 1499. Repair as
required.
4. Transmission temperature too
high.4. Check for transmission over
temp. DTC.
5. Engine coolant temperature too
high.5. (a) Check coolant level. Correct
level as required.
(b) Thermostat stuck. Replace
thermostat.
(c) Water pump failed. Replace
water pump.
(d) Coolant flow restricted. Clean
radiator.
(e) Air flow over radiator
obstructed.Remove obstruction.
KJCOOLING 7 - 11
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
BELT BROKEN (NOTE: IDENTIFY
AND CORRECT PROBLEM
BEFORE NEW BELT IS
INSTALLED)1. Excessive tension. 1. Replace belt and automatic belt
tensioner.
2. Incorrect belt. 2. Replace belt.
3. Tensile member damaged during
belt installation.3. Replace belt.
4. Severe misalignment. 4. Check and replace.
5. Bracket, pulley, or bearing failure. 5. Replace defective component
and belt.
NOISE (OBJECTIONABLE
SQUEAL, SQUEAK, OR RUMBLE
IS HEARD OR FELT WHILE
DRIVE BELT IS IN OPERATION)1. Belt slippage. 1. Replace belt or automatic belt
tensioner.
2. Bearing noise. 2. Locate and repair.
3. Belt misalignment. 3. Replace belt.
4. Belt-to-pulley mismatch. 4. Install correct belt.
BELT TENSIONERS
REMOVAL - 3.7L ENGINE
(1) Remove accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(2) Remove tensioner assembly from engine front
cover (Fig. 2).WARNING: BECAUSE OF HIGH SPRING TENSION,
DO NOT ATTEMPT TO DISASSEMBLE AUTOMATIC
TENSIONER. UNIT IS SERVICED AS AN ASSEMBLY
(EXCEPT FOR PULLEY ON TENSIONER).
(3) Remove pulley bolt. Remove pulley from ten-
sioner.
INSTALLATION - 3.7L ENGINE
(1) Install pulley and pulley bolt to tensioner.
Tighten bolt to 61 N´m (45 ft. lbs.) torque.
(2) An indexing slot is located on back of tensioner.
Align this slot to the head of the bolt on the front
cover. Install the mounting bolt. Tighten bolt to 41
N´m (30 ft. lbs.).
(3) Install drive belt (Refer to 7 - COOLING/AC-
CESSORY DRIVE/DRIVE BELTS - INSTALLA-
TION).
(4) Check belt indexing marks (Refer to 7 - COOL-
ING/ACCESSORY DRIVE/DRIVE BELTS - INSTAL-
LATION).
DRIVE BELTS - 3.7L
REMOVAL - 3.7L ENGINE
NOTE: The belt routing schematics are published
from the latest information available at the time of
publication. If anything differs between these sche-
matics and the Belt Routing Label, use the sche-
matics on Belt Routing Label. This label is located
in the engine compartment.
Fig. 2 Automatic Belt Tensioner
1 - TIMING CHAIN COVER
2 - BOLT TORQUE TO 41 N´m (30 FT LBS)
3 - AUTOMATIC BELT TENSIONER
KJACCESSORY DRIVE 7 - 17
ACCESSORY DRIVE (Continued)

CAUTION: DO NOT LET TENSIONER ARM SNAP
BACK TO THE FREEARM POSITION, SEVERE DAM-
AGE MAY OCCUR TO THE TENSIONER.
Belt tension is not adjustable. Belt adjustment is
maintained by an automatic ( spring load ) belt ten-
sioner.
(1) Disconnect negative battery cable from battery.
(2) Rotate belt tensioner until it contacts its stop.
Remove belt, then slowly rotate the tensioner into
the freearm position. (Fig. 3).INSTALLATION - 3.7L ENGINE
NOTE: The belt routing schematics are published
from the latest information available at the time of
publication. If anything differs between these sche-
matics and the Belt Routing Label, use the sche-
matics on Belt Routing Label. This label is located
in the engine compartment.
Belt tension is not adjustable. Belt adjustment is
maintained by an automatic ( spring load ) belt ten-
sioner.
(1) Check condition of all pulleys.
CAUTION: When installing the serpentine accessory
drive belt, the belt MUST be routed correctly. If not,
the engine may overheat due to the water pump
rotating in the wrong direction (Fig. 3).
(2) Install new belt (Fig. 3). Route the belt around
all pulleys except the idler pulley. Rotate the ten-
sioner arm until it contacts its stop position. Route
the belt around the idler and slowly let the tensioner
rotate into the belt. Make sure the belt is seated onto
all pulleys.
(3) With the drive belt installed, inspect the belt
wear indicator (Fig. 4). On 3.7L Engines the gap
between the tang and the housing stop ( measure-
ment A ) must not exceed 24 mm (.94 inches).
Fig. 3 Belt Routing - 3.7L
1 - GENERATOR PULLEY
2 - ACCESSORY DRIVE BELT
3 - POWER STEERING PUMP PULLEY
4 - CRANKSHAFT PULLEY
5 - IDLER PULLEY
6 - TENSIONER
7 - A/C COMPRESSOR PULLEY
8 - WATER PUMP PULLEY
Fig. 4 Accessory Drive Belt Wear Indicator
1 - AUTOMATIC TENSIONER ASSEMBLY
7 - 18 ACCESSORY DRIVEKJ
DRIVE BELTS - 3.7L (Continued)

ENGINE
TABLE OF CONTENTS
page page
COOLANT RECOVERY PRESS CONTAINER
DESCRIPTION.........................19
OPERATION...........................19
ENGINE COOLANT TEMPERATURE SENSOR
DESCRIPTION.........................19
OPERATION...........................20
REMOVAL.............................20
INSTALLATION.........................21
ENGINE COOLANT THERMOSTAT
DESCRIPTION - 3.7L ENGINE.............21
OPERATION...........................21
DIAGNOSIS AND TESTING - THERMOSTAT . . . 21
REMOVAL - 3.7L ENGINE.................21
INSTALLATION - 3.7L ENGINE.............22
RADIATOR
DESCRIPTION.........................22
REMOVAL.............................23
CLEANING............................24
INSPECTION..........................24
INSTALLATION.........................24
RADIATOR PRESSURE CAP
DESCRIPTION.........................25
OPERATION...........................25
DIAGNOSIS AND TESTING - RADIATOR
PRESSURE CAP......................25CLEANING............................25
INSPECTION..........................25
RADIATOR FAN - ELECTRIC
DESCRIPTION.........................26
OPERATION...........................26
REMOVAL.............................26
INSTALLATION.........................27
RADIATOR - FAN - VISCOUS
DESCRIPTION.........................27
OPERATION...........................27
DIAGNOSIS AND TESTING - VISCOUS FAN
DRIVE..............................28
REMOVAL.............................28
CLEANING............................29
INSPECTION..........................29
INSTALLATION.........................29
WATER PUMP
DESCRIPTION
DESCRIPTION - WATER PUMP...........29
DESCRIPTION........................29
OPERATION - WATER PUMP..............30
REMOVAL.............................30
CLEANING............................31
INSPECTION..........................31
INSTALLATION.........................31
COOLANT RECOVERY PRESS
CONTAINER
DESCRIPTION
This system works along with the radiator pres-
sure cap. This is done by using thermal expansion
and contraction of the coolant to keep the coolant
free of trapped air. It provides:
²A volume for coolant expansion and contraction.
²A convenient and safe method for checking/ad-
justing coolant level at atmospheric pressure. This is
done without removing the radiator pressure cap.
²Some reserve coolant to the radiator to cover
minor leaks and evaporation or boiling losses.
As the engine cools, a vacuum is formed in the
cooling system of both the radiator and engine. Cool-
ant will then be drawn from the coolant tank and
returned to a proper level in the radiator.
The coolant reservoir/overflow system has a radia-
tor mounted pressurized cap, an overflow tube, and a
plastic coolant reservoir/overflow tank, mounted to
the right side of the cowl. It is mounted to the cowlwith two nuts on top, and a slide bracket on the bot-
tom.
OPERATION
The pressure chamber keeps the coolant free of
trapped air, provides a volume for expansion and con-
traction, and provides a convenient and safe method
for checking and adjusting coolant level at atmo-
spheric pressure. It also provides some reserve cool-
ant to cover minor leaks, evaporation or boiling
losses. The overflow chamber allows coolant recovery
in case of an overheat.
ENGINE COOLANT
TEMPERATURE SENSOR
DESCRIPTION
The Engine Coolant Temperature (ECT) sensor is
used to sense engine coolant temperature. The sensor
protrudes into an engine water jacket.
KJENGINE 7 - 19

INSTALLATION - 3.7L ENGINE
(1) Clean mating areas of timing chain cover and
thermostat housing.
(2)
Install thermostat (spring side down) into
recessed machined groove on timing chain cover (Fig. 4).
(3) Position thermostat housing on timing chain
cover.
(4) Install two housing-to-timing chain cover bolts.
Tighten bolts to 13 N´m (115 in. lbs.) torque.
CAUTION: Housing must be tightened evenly and
thermostat must be centered into recessed groove
in timimg chain cover. If not, it may result in a
cracked housing, damaged timing chain cover
threads or coolant leaks.
(5)
Install lower radiator hose on thermostat housing.
(6) Install splash shield.
(7) Lower vehicle.
(8) Fill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(9) Connect negative battery cable to battery.
(10) Start and warm the engine. Check for leaks.
RADIATOR
DESCRIPTION
All vehicles are equipped with a cross flow type
radiator with plastic side tanks (Fig. 5).Plastic tanks, while stronger than brass, are sub-
ject to damage by impact, such as from tools or
wrenches. Handle radiator with care.
Fig. 4 Thermostat and Thermostat Housing
1 - THERMOSTAT HOUSING
2 - THERMOSTAT LOCATION3 - THERMOSTAT AND GASKET
4 - TIMING CHAIN COVER
Fig. 5 Cross Flow Radiator - Typical
1 - RADIATOR
7 - 22 ENGINEKJ
ENGINE COOLANT THERMOSTAT (Continued)