warning JEEP LIBERTY 2002 KJ / 1.G User Guide

(4) Remove caliper piston withshort burstsof
low pressure compressed air. Direct air through fluid
inlet port and ease piston out of bore (Fig. 18).
CAUTION: Do not blow the piston out of the bore
with sustained air pressure. This could result in a
cracked piston. Use only enough air pressure to
ease the piston out.
WARNING: NEVER ATTEMPT TO CATCH THE PIS-
TON AS IT LEAVES THE BORE. THIS MAY RESULT
IN PERSONAL INJURY.(5) Remove caliper piston dust boot with suitable
pry tool (Fig. 19).
(6) Remove caliper piston seal with wood or plastic
tool (Fig. 20). Do not use metal tools as they will
scratch piston bore.
(7) Remove caliper mounting bolt bushings and
boots (Fig. 21).
Fig. 16 DISC BRAKE CALIPER
1 - DISC BRAKE CALIPER
2 - CALIPER SLIDE MOUNTING BOLTS
3 - BRAKE HOSE
4 - BANJO BOLT
5 - CALIPER ADAPTER MOUNTING BOLT
Fig. 17 PADDING CALIPER INTERIOR - TYPICAL
1 - SHOP TOWELS OR CLOTHS
2 - CALIPER
Fig. 18 CALIPER PISTON REMOVAL - TYPICAL
1 - AIR GUN
2 - CALIPER PISTON
3 - PADDING MATERIAL
Fig. 19 CALIPER PISTON DUST BOOT REMOVAL -
TYPICAL
1 - COLLAPSE BOOT WITH PUNCH OR SCREWDRIVER
2 - PISTON DUST BOOT
KJBRAKES - BASE 5 - 15
DISC BRAKE CALIPERS (Continued)

a linear force against the secondary brake shoe. This
action presses the secondary shoe into contact with
the drum. Once the secondary shoe contacts the
drum, force is exerted through the strut. This force is
transferred through the strut to the primary brake
shoe causing it to pivot into the drum as well.
A gear type ratcheting mechanism is used to hold
the lever in an applied position. Parking brake
release is accomplished by the hand lever release
button.
A parking brake switch is mounted on the parking
brake lever and is actuated by movement of the
lever. The switch, which is in circuit with the red
warning light in the dash, will illuminate the warn-
ing light whenever the parking brakes are applied.
Parking brake is self-adjusting when the lever is
pulled. The cable tensioner, once adjusted at the fac-
tory, should not need further adjustment under nor-
mal circumstances.
ADJUSTMENTS
ADJUSTMENT - LOCK OUT
NOTE: The parking brake is self-adjusting, It can
not be adjusted.
(1) Remove the center floor console (Refer to 23 -
BODY/INTERIOR/FLOOR CONSOLE - REMOVAL).
(2) Pull up on the spring until the tab on the lever
passes the tab on the cable guide and install a punch
in the hole on the side then release (Fig. 46).(3) The park brake system is now locked out to
perform necessary repairs.
CABLES
REMOVAL
(1) Lock out the parking brake cables (Refer to 5 -
BRAKES/PARKING BRAKE - ADJUSTMENTS) (Fig.
46).
(2) Remove the rear seat (Refer to 23 - BODY/
SEATS/SEAT - REMOVAL).
(3) Remove the cable saddle bracket (Fig. 47).
(4) Disconnect the two cables from the front mount
(Fig. 48).
(5) Pull the carpet forward far enough in the rear
to gain access to the two parking brake cables thru
the floor (Fig. 47).
(6) Push the cables thru the floor with the grom-
mets.
(7) Remove the primary brake shoe hold down
spring and separate the shoes to gain access, Then
disconnect the cable from lever on brake shoe.
(8) Remove cables from backing plates by using a
screw driver to break off the tangs on the cable or a
proper sized box end wrench over the tangs.
INSTALLATION
(1) Install the cables into the support plate.
(2) Reconnect the cable to the lever on the brake
shoe, Install the primary brake shoe hold down
spring and the shoes.
Fig. 46 LOCK OUT CABLES
1 - PARKING BRAKE HANDLE
2 - PUNCH
3 - CABLE GUIDE
4 - CABLE
Fig. 47 MOUNTING BRACKETS
1 - MOUNTING SADDLE BRACKET
2 - PARK BRAKE CABLES
3 - CARPET
5 - 30 BRAKES - BASEKJ
PARKING BRAKE (Continued)

BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION.........................32
OPERATION...........................32
DIAGNOSIS AND TESTING - ANTILOCK
BRAKING SYSTEM....................33
STANDARD PROCEDURE - ABS BRAKE
BLEEDING...........................33
SPECIFICATIONS.......................33
ELECTRICAL
DESCRIPTION.........................34
OPERATION...........................34FRONT WHEEL SPEED SENSOR
REMOVAL.............................34
INSTALLATION.........................34
REAR WHEEL SPEED SENSOR
REMOVAL.............................35
INSTALLATION.........................35
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION.........................35
OPERATION...........................35
REMOVAL.............................36
INSTALLATION.........................36
BRAKES - ABS
DESCRIPTION
ANTILOCK BRAKING SYSTEM
The purpose of the antilock system is to prevent
wheel lockup during periods of high wheel slip. Pre-
venting lockup helps maintain vehicle braking action
and steering control.
The antilock CAB activates the system whenever
sensor signals indicate periods of high wheel slip.
High wheel slip can be described as the point where
wheel rotation begins approaching 20 to 30 percent of
actual vehicle speed during braking. Periods of high
wheel slip occur when brake stops involve high pedal
pressure and rate of vehicle deceleration.
Battery voltage is supplied to the CAB ignition ter-
minal when the ignition switch is turned to Run posi-
tion. The CAB performs a system initialization
procedure at this point. Initialization consists of a
static and dynamic self check of system electrical
components.
The static check occurs after the ignition switch is
turned to Run position. The dynamic check occurs
when vehicle road speed reaches approximately 30
kph (18 mph). During the dynamic check, the CAB
briefly cycles the pump and solenoids to verify oper-
ation.
If an ABS component exhibits a fault during ini-
tialization, the CAB illuminates the amber warning
light and registers a fault code in the microprocessor
memory.
ELECTRONIC BRAKE DISTRIBUTION
The electronic brake distribution (EBD) functions
like a rear proportioning valve. The EBD system usesthe ABS system to control the slip of the rear wheels
in partial braking range. The braking force of the
rear wheels is controlled electronically by using the
inlet and outlet valves located in the HCU.
OPERATION
ANTILOCK BRAKING SYSTEM
During normal braking, the master cylinder, power
booster and wheel brake units all function as they
would in a vehicle without ABS. The HCU compo-
nents are not activated.
During antilock braking fluid pressure is modu-
lated according to wheel speed, degree of slip and
rate of deceleration. A sensor at each wheel converts
wheel speed into electrical signals. These signals are
transmitted to the CAB for processing and determi-
nation of wheel slip and deceleration rate.
The ABS system has three fluid pressure control
channels. The front brakes are controlled separately
and the rear brakes in tandem. A speed sensor input
signal indicating a high slip condition activates the
CAB antilock program. Two solenoid valves are used
in each antilock control channel. The valves are all
located within the HCU valve body and work in pairs
to either increase, hold, or decrease apply pressure as
needed in the individual control channels. The sole-
noid valves are not static during antilock braking.
They are cycled continuously to modulate pressure.
Solenoid cycle time in antilock mode can be mea-
sured in milliseconds.
ELECTRONIC BRAKE DISTRIBUTION
Upon entry into EBD the inlet valve for the rear
brake circuit is switched on so that the fluid supply
from the master cylinder is shut off. In order to
decrease the rear brake pressure the outlet valve for
5 - 32 BRAKES - ABSKJ

the rear brake circuit is pulsed. This allows fluid to
enter the low pressure accumulator (LPA) in the
HCU resulting in a drop in fluid pressure to the rear
brakes. In order to increase the rear brake pressure
the outlet valve is switched off and the inlet valve is
pulsed. This increases the pressure to the rear
brakes. This will continue until the required slip dif-
ference is obtained. At the end of EBD braking (no
brake application) the fluid in the LPA drains back to
the master cylinder by switching on the outlet valve
and draining through the inlet valve check valve. At
the same time the inlet valve is switched on to pre-
vent a hydraulic short circiut in case of another
brake application.The EBD will remain functional
during many ABS fault modes. If the red and amber
warning lamps are illuminated the EBD may have a
fault.
DIAGNOSIS AND TESTING - ANTILOCK
BRAKING SYSTEM
The ABS brake system performs several self-tests
every time the ignition switch is turned on and the
vehicle is driven. The CAB monitors the systems
input and output circuits to verify the system is oper-
ating correctly. If the on board diagnostic system
senses that a circuit is malfunctioning the system
will set a trouble code in its memory.
NOTE: An audible noise may be heard during the
self-test. This noise should be considered normal.NOTE: The MDS or DRB III scan tool is used to
diagnose the ABS system. For additional informa-
tion refer to the Electrical, Electronic Control Mod-
ules section. For test procedures refer to the
Chassis Diagnostic Manual.
STANDARD PROCEDURE - ABS BRAKE
BLEEDING
ABS system bleeding requires conventional bleed-
ing methods plus use of the DRB scan tool. The pro-
cedure involves performing a base brake bleeding,
followed by use of the scan tool to cycle and bleed the
HCU pump and solenoids. A second base brake bleed-
ing procedure is then required to remove any air
remaining in the system.
(1) Perform base brake bleeding,(Refer to 5 -
BRAKES - STANDARD PROCEDURE) OR (Refer to
5 - BRAKES - STANDARD PROCEDURE).
(2) Connect scan tool to the Data Link Connector.
(3) Select ANTILOCK BRAKES, followed by MIS-
CELLANEOUS, then ABS BRAKES. Follow the
instructions displayed. When scan tool displays TEST
COMPLETE, disconnect scan tool and proceed.
(4) Perform base brake bleeding a second time,(Re-
fer to 5 - BRAKES - STANDARD PROCEDURE) OR
(Refer to 5 - BRAKES - STANDARD PROCEDURE).
(5) Top off master cylinder fluid level and verify
proper brake operation before moving vehicle.
SPECIFICATIONS
TORQUE SPECIFICATIONS
DESCRIPTION N´m Ft. Lbs. In. Lbs.
Hydraulic Control
Unit/Controller Antilock
Brakes Mounting Nuts14.1 Ð 125
Hydraulic Control
Unit/Controller Antilock
Brakes Brake Lines20.3 Ð 180
Controller Antilock Brakes
Mounting Screws1.8 Ð 16
Wheel Speed Sensors
Front Mounting Bolt12 Ð 132
Wheel Speed Sensor
Rear Mounting Bolt9Ð80
KJBRAKES - ABS 5 - 33
BRAKES - ABS (Continued)

CLUTCH
TABLE OF CONTENTS
page page
CLUTCH
DESCRIPTION..........................1
OPERATION............................1
WARNING.............................2
DIAGNOSIS AND TESTING - CLUTCH........2
SPECIFICATIONS - CLUTCH...............5
CLUTCH DISC
REMOVAL.............................6
INSTALLATION..........................6
CLUTCH RELEASE BEARING
REMOVAL.............................6
INSTALLATION..........................6
FLYWHEEL
DESCRIPTION..........................7
OPERATION............................7
DIAGNOSIS AND TESTING - FLYWHEEL......8
PILOT BEARING
REMOVAL.............................8
INSTALLATION..........................8LINKAGE
REMOVAL.............................8
INSTALLATION..........................9
MASTER CYLINDER
INSPECTION...........................9
CLUTCH PEDAL
REMOVAL.............................10
INSTALLATION.........................10
CLUTCH SWITCH OVERRIDE RELAY
DESCRIPTION.........................10
OPERATION...........................10
REMOVAL.............................10
INSTALLATION.........................10
CLUTCH PEDAL POSITION SWITCH
DESCRIPTION.........................11
OPERATION...........................11
DIAGNOSIS AND TESTING - CLUTCH PEDAL
POSITION SWITCH....................11
CLUTCH
DESCRIPTION
The clutch mechanism consists of a flywheel, dry-
type disc, diaphragm style pressure plate and
hydraulic linkage. The flywheel is bolted to the rear
flange of the crankshaft. The clutch pressure plate is
bolted to the flywheel with the clutch disc between
these two components. The clutch system provides
the mechanical, link between the engine and the
transmission. The system is designed to transfer the
torque output of the engine, to the transmission
while isolating the transmission from the engine fir-
ing pulses to minimize concerns such as gear rattle.
OPERATION
The clutch operates with leverage, clamping force
and friction. The disc serves as the friction element,
the diaphragm spring and pressure plate provide the
clamping force. The clutch pedal, hydraulic linkage,
release lever and bearing provide the leverage.
The clutch master cylinder push rod is connected
to the clutch pedal. When the clutch pedal is
depressed, the slave cylinder is operated by the
clutch master cylinder mounted on the dash panel.
The release fork is actuated by the hydraulic slave
cylinder mounted on the transmission housing. The
release bearing is operated by a release fork pivoting
on a ball stud mounted in the transmission housing.
The release bearing then depresses the pressure
plate spring fingers, thereby releasing pressure on
the clutch disc and allowing the engine crankshaft to
spin independently of the transmission input shaft.
KJCLUTCH 6 - 1

WARNING
WARNING:: EXERCISE CARE WHEN SERVICING
CLUTCH COMPONENTS. FACTORY INSTALLED
CLUTCH DISCS DO NOT CONTAIN ASBESTOS
FIBERS. DUST AND DIRT ON CLUTCH PARTS MAY
CONTAIN ASBESTOS FIBERS FROM AFTERMAR-
KET COMPONENTS. BREATHING EXCESSIVE CON-
CENTRATIONS OF THESE FIBERS CAN CAUSE
SERIOUS BODILY HARM. WEAR A RESPIRATOR
DURING SERVICE AND NEVER CLEAN CLUTCH
COMPONENTS WITH COMPRESSED AIR OR WITH
A DRY BRUSH. EITHER CLEAN THE COMPONENTS
WITH A WATER DAMPENED RAGS OR USE A VAC-
UUM CLEANER SPECIFICALLY DESIGNED FOR
REMOVING ASBESTOS FIBERS AND DUST. DO NOT
CREATE DUST BY SANDING A CLUTCH DISC.
REPLACE THE DISC IF THE FRICTION MATERIAL IS
DAMAGED OR CONTAMINATED. DISPOSE OF ALL
DUST AND DIRT CONTAINING ASBESTOS FIBERS
IN SEALED BAGS OR CONTAINERS. THIS WILL
HELP MINIMIZE EXPOSURE TO YOURSELF AND TO
OTHERS. FOLLOW ALL RECOMMENDED SAFETY
PRACTICES PRESCRIBED BY THE OCCUPATIONAL
SAFETY AND HEALTH ADMINISTRATION (OSHA)
AND THE ENVIRONMENTAL SAFETY AGENCY
(EPA), FOR THE HANDLING AND DISPOSAL OF
PRODUCTS CONTAINING ASBESTOS.
DIAGNOSIS AND TESTING - CLUTCH
Drive the vehicle at normal speeds. Shift the trans-
mission through all gear ranges and observe clutch
action. If the clutch chatters, grabs, slips or does not
release properly, remove and inspect the clutch com-
ponents. If the problem is noise or hard shifting, fur-
ther diagnosis may be needed as the transmission or
another driveline component may be at fault.
NOTE: Vehicles equipped with a Dual Mass Fly-
wheel may produce a rattle when the engine is shut
off. This noise is considered normal.
CLUTCH CONTAMINATION
Fluid contamination is a frequent cause of clutch
malfunctions. Oil, water or clutch fluid on the clutch
disc and pressure plate surfaces will cause chatter,
slip and grab. Inspect components for oil, hydraulic
fluid or water/road splash contamination.
Oil contamination indicates a leak at either the
rear main seal or transmission input shaft. Clutch
fluid leaks are usually from damaged slave cylinder
push rod seals. Heat buildup caused by slippage
between the pressure plate, disc and flywheel can
bake the oil residue onto the components. The glaze-
like residue ranges in color from amber to black.Road splash contamination is dirt/water entering
the clutch housing due to loose bolts, housing cracks.
Driving through deep water puddles can force water/
road splash into the housing through such openings.
IMPROPER RELEASE OR CLUTCH ENGAGEMENT
Clutch release or engagement problems are caused
by wear or damage clutch components. A visual
inspection of the release components will usually
reveal the problem part.
Release problems can result in hard shifting and
noise. Look for leaks at the clutch cylinders and
interconnecting line and loose slave cylinder bolts.
Also worn/loose release fork, pivot stud, clutch disc,
pressure plate or release bearing.
Engagement problems can result in slip, chatter/
shudder and noisy operation. The causes may be
clutch disc contamination, wear, distortion or fly-
wheel damage. Visually inspect to determine the
actual cause of the problem.
CLUTCH MISALIGNMENT
Clutch components must be in proper alignment
with the crankshaft and transmission input shaft.
Misalignment caused by excessive runout or warpage
of any clutch component will cause grab, chatter and
improper clutch release.
PRESSURE PLATE AND DISC RUNOUT
Check the clutch disc before installation. Axial
(face) runout of anewdisc should not exceed 0.50
mm (0.020 in.). Measure runout about 6 mm (1/4 in.)
from the outer edge of the disc facing. Obtain
another disc if runout is excessive.
Check condition of the clutch before installation. A
warped cover or diaphragm spring will cause grab
and incomplete release or engagement. Be careful
when handling the cover and disc. Impact can distort
the cover, diaphragm spring, release fingers and the
hub of the clutch disc.
Use an alignment tool when positioning the disc on
the flywheel. The tool prevents accidental misalign-
ment which could result in cover distortion and disc
damage.
A frequent cause of clutch cover distortion (and
consequent misalignment) is improper bolt tighten-
ing.
FLYWHEEL RUNOUT
Check flywheel runout whenever misalignment is
suspected. Flywheel runout should not exceed 0.08
mm (0.003 in.). Measure runout at the outer edge of
the flywheel face with a dial indicator. Mount the
indicator on a stud installed in place of one of the fly-
wheel bolts.
6 - 2 CLUTCHKJ
CLUTCH (Continued)

DESCRIPTION - COOLING SYSTEM ROUTING
3.7L ENGINE
For cooling system routing refer to (Fig. 1).
DESCRIPTION - HOSE CLAMPS
The cooling system utilizes spring type hose
clamps. If a spring type clamp replacement is neces-
sary, replace with the original Mopartequipment
spring type clamp.
WARNING: CONSTANT TENSION HOSE CLAMPS
ARE USED ON MOST COOLING SYSTEM HOSES.
WHEN REMOVING OR INSTALLING, USE ONLY
TOOLS DESIGNED FOR SERVICING THIS TYPE OF
CLAMP, SUCH AS SPECIAL CLAMP TOOL (NUMBER
6094) (Fig. 2). SNAP-ON CLAMP TOOL (NUMBER
HPC-20) MAY BE USED FOR LARGER CLAMPS.ALWAYS WEAR SAFETY GLASSES WHEN SERVIC-
ING CONSTANT TENSION CLAMPS.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only a original equipment clamp
with matching number or letter (Fig. 2).
OPERATION
OPERATION - COOLING SYSTEM
The cooling system regulates engine operating tem-
perature. It allows the engine to reach normal oper-
ating temperature as quickly as possible. It also
maintains normal operating temperature and pre-
vents overheating.
Fig. 1 Engine Cooling System 3.7L Engine
1 - LH CYL. HEAD
2 - AIR BLEED
3 - THERMOSTAT LOCATION
4 - RH CYL. HEAD5 - RH BANK CYL. BLOCK
6 - LH BANK CYL. BLOCK
7 - COOLANT TEMP. SENSOR
7 - 2 COOLINGKJ
COOLING (Continued)

DIAGNOSIS AND TESTING - COOLING SYSTEM
LEAKS
ULTRAVIOLET LIGHT METHOD
A leak detection additive is available through the
parts department that can be added to cooling sys-
tem. The additive is highly visible under ultraviolet
light (black light). Pour one ounce of additive into
cooling system. Place heater control unit in HEAT
position. Start and operate engine until radiator
upper hose is warm to touch. Aim the commercially
available black light tool at components to be
checked. If leaks are present, black light will cause
additive to glow a bright green color.
The black light can be used in conjunction with a
pressure tester to determine if any external leaks
exist (Fig. 3).
PRESSURE TESTER METHOD
The engine should be at normal operating temper-
ature. Recheck the system cold if cause of coolant
loss is not located during the warm engine examina-
tion.
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING.
Carefully remove radiator pressure cap from pres-
sure bottle and check coolant level. Push down on
cap to disengage it from stop tabs. Wipe inside of
filler neck and examine lower inside sealing seat fornicks, cracks, paint, and dirt. Inspect radiator-to-
reserve/overflow tank hose for internal obstructions.
Insert a wire through the hose to be sure it is not
obstructed.
Inspect cams on outside of filler neck. If cams are
damaged, seating of pressure cap valve and tester
seal will be affected.
Attach pressure tester (7700 or an equivalent) to
radiator filler neck (Fig. 4).
Operate tester pump to apply 110 kPa (16 psi)
pressure to system. If hoses enlarge excessively or
bulges while testing, replace as necessary. Observe
gauge pointer and determine condition of cooling sys-
tem according to following criteria:
Holds Steady:If pointer remains steady for two
minutes, serious coolant leaks are not present in sys-
tem. However, there could be an internal leak that
does not appear with normal system test pressure. If
it is certain that coolant is being lost and leaks can-
not be detected, inspect for interior leakage or per-
form Internal Leakage Test.
Drops Slowly:Indicates a small leak or seepage
is occurring. Examine all connections for seepage or
slight leakage with a flashlight. Inspect radiator,
hoses, gasket edges and heater. Seal small leak holes
with a Sealer Lubricant (or equivalent). Repair leak
holes and inspect system again with pressure
applied.
Drops Quickly:Indicates that serious leakage is
occurring. Examine system for external leakage. If
leaks are not visible, inspect for internal leakage.
Large radiator leak holes should be repaired by a
reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION
Remove engine oil pan drain plug and drain a
small amount of engine oil. If coolant is present in
Fig. 3 Leak Detection Using Black Light - Typical
1 - TYPICAL BLACK LIGHT TOOL
Fig. 4 Pressure Testing Cooling System - Typical
1 - TYPICAL COOLING SYSTEM PRESSURE TESTER
7 - 4 COOLINGKJ
COOLING (Continued)

the pan, it will drain first because it is heavier than
oil. An alternative method is to operate engine for a
short period to churn the oil. After this is done,
remove engine dipstick and inspect for water glob-
ules. Also inspect transmission dipstick for water
globules and transmission fluid cooler for leakage.
WARNING: WITH RADIATOR PRESSURE TESTER
TOOL INSTALLED ON RADIATOR, DO NOT ALLOW
PRESSURE TO EXCEED 124 KPA (18 PSI). PRES-
SURE WILL BUILD UP QUICKLY IF A COMBUSTION
LEAK IS PRESENT. TO RELEASE PRESSURE,
ROCK TESTER FROM SIDE TO SIDE. WHEN
REMOVING TESTER, DO NOT TURN TESTER MORE
THAN 1/2 TURN IF SYSTEM IS UNDER PRESSURE.
Operate engine without pressure cap on radiator
until thermostat opens. Attach a Pressure Tester to
filler neck. If pressure builds up quickly it indicates a
combustion leak exists. This is usually the result of a
cylinder head gasket leak or crack in engine. Repair
as necessary.
If there is not an immediate pressure increase,
pump the Pressure Tester. Do this until indicated
pressure is within system range of 110 kPa (16 psi).
Fluctuation of gauge pointer indicates compression or
combustion leakage into cooling system.
Because the vehicle is equipped with a catalytic
converter,do notremove spark plug cables or short
out cylinders to isolate compression leak.
If the needle on dial of pressure tester does not
fluctuate, race engine a few times to check for an
abnormal amount of coolant or steam. This would be
emitting from exhaust pipe. Coolant or steam from
exhaust pipe may indicate a faulty cylinder head gas-
ket, cracked engine cylinder block or cylinder head.A convenient check for exhaust gas leakage into
cooling system is provided by a commercially avail-
able Block Leak Check tool. Follow manufacturers
instructions when using this product.
COMBUSTION LEAKAGE TEST - WITHOUT
PRESSURE TESTER
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
WARNING: DO NOT REMOVE CYLINDER BLOCK
DRAIN PLUGS OR LOOSEN RADIATOR DRAIN-
COCK WITH SYSTEM HOT AND UNDER PRESSURE.
SERIOUS BURNS FROM COOLANT CAN OCCUR.
Drain sufficient coolant to allow thermostat
removal. (Refer to 7 - COOLING/ENGINE/ENGINE
COOLANT THERMOSTAT - REMOVAL). Remove
accessory drive belt (Refer to 7 - COOLING/ACCES-
SORY DRIVE/DRIVE BELTS - REMOVAL).
Add coolant to radiator to bring level to within 6.3
mm (1/4 in) of top of thermostat housing.
CAUTION: Avoid overheating. Do not operate
engine for an excessive period of time. Open drain-
cock immediately after test to eliminate boil over.
Start engine and accelerate rapidly three times, to
approximately 3000 rpm while observing coolant. If
internal engine combustion gases are leaking into
cooling system, bubbles will appear in coolant. If bub-
bles do not appear, internal combustion gas leakage
is not present.
KJCOOLING 7 - 5
COOLING (Continued)

DIAGNOSIS AND TESTING - COOLING SYSTEM DIAGNOSIS CHART
COOLING SYSTEM DIAGNOSIS CHART
CONDITION POSSIBLE CAUSES CORRECTION
TEMPERATURE GAUGE READS
LOW1. Has a Diagnostic Trouble Code
(DTC) been set indicating a stuck
open thermostat?1. Refer to (Refer to 25 -
EMISSIONS CONTROL -
DESCRIPTION) for On-Board
Diagnostics and DTC information.
Replace thermostat if necessary.
2. Is the temperature sending unit
connected?2. Check the temperature sensor
connector. (Refer to 7 - COOLING/
ENGINE/ENGINE COOLANT TEMP
SENSOR - DESCRIPTION). Repair
connector if necessary.
3. Is the temperature gauge
operating OK?3. Check gauge operation. Repair
as necessary.
4. Coolant level low in cold ambient
temperatures accompanied with
poor heater performance.4. Check coolant level in the coolant
pressure botttle and the radiator.
Inspect system for leaks. Repair
leaks as necessary.
5. Improper operation of internal
heater doors or heater controls.5. Inspect heater and repair as
necessary. (Refer to 24 - HEATING
& AIR CONDITIONING -
DIAGNOSIS AND TESTING)
6. Electric fan functioning when not
required.6. 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.
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.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 the normal range,
determine the cause for overheating
and repair.
2. Is the temperature gauge reading
correctly?2. Check gauge. (Refer to Group 8J
- INSTRUMENT CLUSTER). Repair
as necessary.
3. Is the temperature warning
illuminating unnecessarily?3. Check warning lamp operation.
(Refer to Group 8J - INSTRUMENT
CLUSTER).Repair as necessary.
4. Coolant low in coolant pressure
bottle and radiator?4. Check for coolant leaks and
repair as necessary. (Refer to 7 -
COOLING - DIAGNOSIS AND
TESTING).
7 - 6 COOLINGKJ
COOLING (Continued)