1995 JEEP CHEROKEE thermostat

WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING.
Carefully remove the radiator pressure cap from
the filler neck and check the coolant level. Push
down on the cap to disengage it from the stop tabs.
Wipe the inner part of the filler neck and examine
the lower inside sealing seat for nicks, cracks, paint,
dirt and solder residue. Inspect the reserve/overflow
tank tube for internal obstructions. Insert a wire
through the tube to be sure it is not obstructed.
Inspect the cams on the outside part of the filler
neck. If the cams are bent, seating of pressure cap
valve and tester seal will be affected. Replace cap if
cams are bent.
Attach pressure tester 7700 (or an equivalent) to
the radiator filler neck (Fig. 21).Operate the tester pump to apply 124 kPa (18 psi)
pressure to the system. If the hoses enlarge exces-
sively or bulge while testing, replace as necessary.
Observe the gauge pointer and determine the condi-
tion of the cooling system according to the following
criteria:
²Holds Steady: If the pointer remains steady for
two minutes, there are no serious coolant leaks in
the system. However, there could be an internal leak
that does not appear with normal system test pres-
sure. Inspect for interior leakage or do the Internal
Leakage Test. Do this if it is certain that coolant is
being lost and no leaks can be detected.
²Drops Slowly: Shows a small leak or seepage is oc-
curring. Examine all connections for seepage or slight
leakage with a flashlight. Inspect the radiator, hoses,
gasket edges and heater. Seal any small leak holes
with a Sealer Lubricant or equivalent. Repair leak
holes and reinspect the system with pressure ap-
plied.
²Drops Quickly: Shows that a serious leakage is oc-
curring. Examine the system for serious external
leakage. If no leaks are visible, inspect for internal
leakage. Large radiator leak holes should be repaired
by a reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION
Remove the engine oil pan drain plug and drain a
small amount of engine oil. Coolant, being heavier
than engine oil, will drain first. Another way of test-
ing is to operate the engine and check for water glob-
ules on the engine oil dipstick. Also inspect the
automatic transmission oil dipstick for water glob-
ules. Inspect the automatic transmission fluid cooler
for leakage. Operate the engine without the pressure
cap on the radiator until thermostat opens.
Attach a pressure tester to the filler neck. If pres-
sure builds up quickly, a leak exists as a result of a
faulty cylinder head gasket or crack in the engine.
Repair as necessary.
WARNING: DO NOT ALLOW PRESSURE TO EX-
CEED 124 KPA (18 PSI). TURN THE ENGINE OFF.
TO RELEASE THE PRESSURE, ROCK THE TESTER
FROM SIDE TO SIDE. WHEN REMOVING THE
TESTER, DO NOT TURN THE TESTER MORE THAN
1/2 TURN IF THE SYSTEM IS UNDER PRESSURE.
If there is no immediate pressure increase, pump
the pressure tester until the indicated pressure is
within the system range. Vibration of the gauge
pointer indicates compression or combustion leakage
into the cooling system.
WARNING: DO NOT DISCONNECT THE SPARK
PLUG WIRES WHILE THE ENGINE IS OPERATING.
Fig. 20 Leak Detection Using Black LightÐTypical
Fig. 21 Pressurizing SystemÐTypical
JCOOLING SYSTEM SERVICE PROCEDURES 7 - 23

CAUTION: Do not operate the engine with a spark
plug shorted for more than a minute. The catalytic
converter may be damaged.
Isolate the compression leak by shorting each
spark plug to the cylinder block. The gauge pointer
should stop or decrease vibration when spark plug
for leaking cylinder is shorted. This happens because
of the absence of combustion pressure.
COMBUSTION LEAKAGE TEST (WITHOUT
PRESSURE TESTER)
DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM COOLANT
CAN OCCUR.
Drain sufficient coolant to allow for thermostat re-
moval. Refer to Thermostat Replacement. Disconnect
the water pump drive belt.
Disconnect the upper radiator hose from the ther-
mostat housing. Remove the housing and thermostat.
Install the thermostat housing.
Add coolant to the radiator to bring the level to
within 6.3 mm (1/4 in) of the top of the thermostat
housing.
CAUTION: Avoid overheating. Do not operate the
engine for an excessive period of time. Open the
draincock immediately after the test to eliminate
boil over of coolant.
Start the engine and accelerate rapidly three times
(to approximately 3000 rpm) while observing the
coolant. If internal engine combustion gases are leak-
ing into the cooling system, bubbles will appear in
the coolant. If bubbles do not appear, there is no in-
ternal combustion gas leakage.
COOLANT RESERVE/OVERFLOW SYSTEM
The system works along with the radiator pressure
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/adjust-
ing coolant level at atmospheric pressure. This is
done without removing the radiator pressure cap.
²Some reserve coolant to the radiator to cover mi-
nor 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 re-
turned to a proper level in the radiator.
The coolant reserve/overflow system consists of a
radiator mounted pressurized cap, a plastic reserve/
overflow tank (Figs. 22, 23 or 24), a tube (hose) con-
necting the radiator and tank, and an overflow tube
on the side of the tank.
Fig. 22 Reserve/Overflow TankÐYJ Models
Fig. 23 Reserve/Overflow TankÐXJ ModelsÐExcept
Right Hand Drive
7 - 24 COOLING SYSTEM SERVICE PROCEDURESJ

(4) When checking for vacuum leaks.
WARNING: IF VEHICLE HAS BEEN RUN RECENTLY,
WAIT AT LEAST 15 MINUTES BEFORE REMOVING
RADIATOR CAP. WITH A RAG, SQUEEZE RADIATOR
UPPER HOSE TO CHECK IF SYSTEM IS UNDER
PRESSURE. PLACE A RAG OVER THE CAP AND
WITHOUT PUSHING DOWN, ROTATE CAP
COUNTER-CLOCKWISE TO THE FIRST STOP. AL-
LOW FLUID TO ESCAPE THROUGH OVERFLOW
HOSE INTO COOLANT RESERVE/OVERFLOW
TANK. SQUEEZE RADIATOR UPPER HOSE TO DE-
TERMINE WHEN PRESSURE HAS BEEN RE-
LEASED. WHEN COOLANT AND STEAM STOP
BEING PUSHED INTO TANK AND SYSTEM PRES-
SURE DROPS, REMOVE RADIATOR CAP COM-
PLETELY.
PRESSURE TESTING RADIATOR CAPS
Remove cap from radiator. Be sure that sealing
surfaces are clean. Moisten rubber gasket with water
and install the cap on pressure tester (tool 7700 or
an equivalent) (Fig. 26).
Operate the tester pump and observe the gauge
pointer at its highest point. The cap release pressure
should be 83-to-110 kPa (12-to-16 psi). The cap is sat-
isfactory when the pressure holds steady. It is also
good if it holds pressure within the 83-to-110 kPa
(12-to-16 psi) range for 30 seconds or more. If the
pointer drops quickly, replace the cap.
CAUTION: Radiator pressure testing tools are very
sensitive to small air leaks, which will not causecooling system problems. A pressure cap that does
not have a history of coolant loss should not be re-
placed just because it leaks slowly when tested
with this tool. Add water to tool. Turn tool upside
down and recheck pressure cap to confirm that cap
needs replacement.
INSPECTION
Visually inspect the pressure valve gasket on the
cap. Replace cap if the gasket is swollen, torn or
worn. Inspect the area around radiator filler neck for
white deposits that indicate a leaking cap.
RADIATORS
GENERAL INFORMATION
All radiators are down flow types except XJ models
equipped with 4.0L 6-cylinder engines. Radiators in
XJ models equipped with the 4.0L 6-cylinder engine
are the cross flow type. Plastic tanks are used on all
radiators.
CAUTION: Plastic tanks, while stronger than brass,
are subject to damage by impact, such as
wrenches.
If the plastic tank has been damaged, the plastic
tank and/or o-rings are available for service repair.
Tank replacement should be done by qualified per-
sonal with proper equipment.
RADIATOR COOLANT FLOW CHECK
The following procedure will determine if coolant is
flowing through the cooling system.
If engine is cold, idle engine until normal operating
temperature is reached. Then feel the upper radiator
hose. If hose is hot, the thermostat is open and water
is circulating through cooling system.
RADIATOR CLEANING
The radiator and air conditioning fins should be
cleaned when an accumulation of bugs, leaves etc.
has occurred. Clean radiator fins are necessary for
good heat transfer. With the engine cold, apply cold
water and compressed air to the back (engine side) of
the radiator to flush the radiator and/or A/C con-
denser of debris.
RADIATOR REMOVAL/INSTALLATION
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS, RADIATOR CAP, OR
LOOSEN THE RADIATOR DRAINCOCK WITH THE
SYSTEM HOT AND PRESSURIZED. SERIOUS
BURNS FROM THE COOLANT CAN OCCUR.
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
Fig. 26 Pressure Testing Radiator Pressure
CapÐTypical
7 - 26 COOLING SYSTEM SERVICE PROCEDURESJ

VISCOUS FAN DRIVE
DESCRIPTION AND OPERATION
Also refer to the previous section on Cooling Sys-
tem Fans.
The thermal viscous fan drive (Fig. 38 or 39) is a
silicone-fluid-filled coupling used to connect the fan
blades to either the engine or the water pump shaft.
The coupling allows the fan to be driven in a normal
manner. This is done at low engine speeds while lim-
iting the top speed of the fan to a predetermined
maximum level at higher engine speeds.
A thermostatic bimetallic spring coil is located on
the front face of the viscous fan drive unit (a typical
viscous unit is shown in figure 40). This spring coil
reacts to the temperature of the radiator discharge
air. It engages the viscous fan drive for higher fan
speed if the air temperature from the radiator rises
above a certain point. Until additional engine cooling
is necessary, the fan will remain at a reduced rpm re-
gardless of engine speed.
Only when sufficient heat is present, will the vis-
cous fan drive engage. This is when the air flowing
through the radiator core causes a reaction to the bi-
metallic coil. It then increases fan speed to provide
the necessary additional engine cooling.
Once the engine has cooled, the radiator discharge
temperature will drop. The bimetallic coil again re-
acts and the fan speed is reduced to the previous dis-
engaged speed.
CAUTION: Engines equipped with serpentine drive
belts have reverse rotating fans and viscous fan
drives. They are marked with the word REVERSE to
designate their usage. Installation of the wrong fan
or viscous fan drive can result in engine overheat-
ing.CAUTION: If the viscous fan drive is replaced be-
cause of mechanical damage, the cooling fan
blades should also be inspected. Inspect for fatigue
cracks, loose blades, or loose rivets that could
have resulted from excessive vibration. Replace fan
blade assembly if any of these conditions are
found. Also inspect water pump bearing and shaft
assembly for any related damage due to a viscous
fan drive malfunction.
NOISE
It is normal for fan noise to be louder (roar-
ing) when:
²The underhood temperature is above the engage-
ment point for the viscous drive coupling. This may
occur when ambient (outside air temperature) is very
high.
²Engine loads and temperatures are high such as
when towing a trailer.
²Cool silicone fluid within the fan drive unit is be-
ing redistributed back to its normal disengaged
(warm) position. This can occur during the first 15
seconds to one minute after engine start-up on a cold
engine.
LEAKS
Viscous fan drive operation is not affected by small
oil stains near the drive bearing. If leakage appears
excessive, replace the fan drive unit.
TESTING
If the fan assembly free-wheels without drag (the
fan blades will revolve more than five turns when
spun by hand), replace the fan drive. This spin test
must be performed when the engine is cool.
For the following test, the cooling system must be
in good condition. It also will ensure against exces-
sively high coolant temperature.
WARNING: BE SURE THAT THERE IS ADEQUATE
FAN BLADE CLEARANCE BEFORE DRILLING.
(1) Drill a 3.18-mm (1/8-in) diameter hole in the
top center of the fan shroud.
(2) Obtain a dial thermometer with an 8 inch stem
(or equivalent). It should have a range of -18É-to-
105ÉC (0É-to-220É F). Insert thermometer through the
hole in the shroud. Be sure that there is adequate
clearance from the fan blades.
(3) Connect a tachometer and an engine ignition
timing light (timing light is to be used as a strobe
light).
(4) Block the air flow through the radiator. Secure
a sheet of plastic in front of the radiator (or air con-
ditioner condenser). Use tape at the top to secure the
plastic and be sure that the air flow is blocked.
Fig. 40 Typical Viscous Fan Drive
7 - 34 COOLING SYSTEM SERVICE PROCEDURESJ

CONNECTOR LOCATIONS
GENERAL INFORMATION
This section provides illustrations identifying com-
ponent and connector locations in the vehicle. A con-nector index is provided. Use the wiring diagrams in
each section for connector number identification. Re-
fer to the index for the proper figure number.
CONNECTOR LOCATIONS
Connector # Color Location Fig.
C101......BK ...Front of Left Fender Side Shield . . .1, 2
C102......BK ...Bottom Right of Radiator Closure
Panel....................8
C103......BK ...Near Left Side of Radiator......2,8
C104......BK ...Left Fender Side Shield
C105......BK ...Bottom of Left Fender Side Shield . . .2
C106......BK ...Left Fender Side Shield, Near PCM .1, 2
C107......BK ...OnABSPump Motor...........2
C108......BK ...Right Rear Corner of Engine
Compartment.............2,3
C109......BK ...Center of Dash Panel.........1,4
C110......BK ...Center of I.P., Below ABS Control
Module...............13, 14
C111......BK ...Left of Steering Column.........14
C112......BK ...AtABSControl Module.........13
C113......BK ...InHarness, Near ABS Control
Module.................13
C114......BK ...Center of I.P., Below ABS Control
Module.................14
C115......BK ...Near ABS Control Module.......14
C116......BK ...Below ABS Control Module.......14
C117......BK ...Rear of Intake Manifold........6,7
C118......BK ...OnThrottle Body............6,7
C119......BK ...Bottom Left Front of Cylinder
Block..................6,7
C120......BK ...OnThrottle Body............6,7
C121......GY ...Rear of Intake Manifold........6,7
C122......BK ...AtThermostat Housing........6,7
C123......BK ...Injector No. 1..............6,7
C124......BK ...Injector No. 2..............6,7
C125......BK ...Injector No. 3..............6,7
C126......BK ...Injector No. 4..............6,7
C127......BK ...Injector No. 5................7
C128......BK ...Injector No. 6................7
C129......GN ...Center of Dash Panel.........1,4
C130......BK ...Below Brake Master Cylinder.....1,2
C131......BK ...Distributor................6,7
C132......GN ...Lower Right Side of I.P.
C133......BK ...Right of Blower Motor..........4
C134......GY ...Right of Blower Motor..........4
C135......GY ...Right of Blower Motor..........4
C136......BR ...OnWasher Fluid Reservoir......1,4
C137......BK ...Under Side of Hood..........1,4
C138......BK ...Left of Blower Motor...........4
C139......BK ...Bottom of Washer Fluid Reservoir .3, 4
C140......BK ...Bottom of Washer Fluid Reservoir .3, 4
C141......BK ...InFront of Washer Fluid Reservoir .1, 4
C142......BK ...Between PDC and Blower Motor . .1, 4Connector # Color Location Fig.
C143......BK ...Bottom Front of Right Fender
Side Shield..............1,3
C144......BK ...Front of Right Fender Side Shield . .1, 3
C145......BK ...Front of Right Fender Side Shield . .1, 3
C146......BK ...Right Side of Grille Opening.....1,3
C147......BK ...Below Distributor..............7
C148......BK ...Right Side of Engine..........6,7
C149......BK ...Rear of Generator...........5,6
C150......BK ...Right Rear of Engine...........7
C151......BK ...Right Fender Side Shield.......1,4
C152......GY ...Behind Power Steering Pump......6
C153......BK ...Right Side of Transmission.......21
C154......BK ...Left Side of Radiator Closure Panel . .8
C155......BK ...Left Rear of Radiator Closure Panel . .8
C156......BK ...Behind Lens.................8
C157......BK ...Behind Left Headlamp...........8
C158......BK ...Behind Lens.................8
C159......BK ...Center of Grille Opening.........8
C160......BK ...Behind Lens.................8
C161......BK ...Behind Right Headlamp..........8
C162......BK ...Behind Lens.................8
C163......BK ...Center of Grille Opening.........8
C164......BK ...Right Center of Engine Compartment
C201......BK ...Below Left Side of I.P.........9,14
C202......LG ...Behind Left Kick Panel.........14
C203......BK ...Behind Left Kick Panel.........14
C204......GY ...Behind Left Kick Panel.........14
C205......BK ...Bottom Right of I.P............12
C206......BK ...Bottom Right of I.P............12
C207......BK ...Behind Headlamp Switch........10
C208......BK ...Bottom Right of I.P............12
C209......BK ...OnI.P.Right of Steering Column . . .10
C210......BK ...OnI.P.Right of Steering Column . . .10
C211......BK ...Rear of Radio...............11
C212......BR ...Center of I.P.................10
C213......BK ...Center of I.P.................10
C214......GY ...Right Side of I.P..............13
C215......BK ...Right Side of I.P..............13
C216......GY ...Glove Box.................10
C217......BK ...Bottom Right of I.P............11
C218......RD ...Right Side of I.P...........13, 17
C219......BK ...Bottom Right of I.P............11
C220......BK ...Right Side of I.P..............13
C221......BK ...Right Corner of I.P............13
C222......LG ...Right Corner of I.P............13
C223......BK ...Right Front of Steering Column....14
C224......BK ...Right Front of Steering Column....14
C225......NAT...Below Steering Column.........14
J8W-90 CONNECTOR LOCATIONSÐXJ VEHICLES 8W - 90 - 1

CONNECTOR LOCATIONS
GENERAL INFORMATION
This section provides illustrations identifying com-
ponent and connector locations in the vehicle. A con-nector index is provided. Use the wiring diagrams in
each section for connector number identification. Re-
fer to the index for the proper figure number.
CONNECTOR LOCATIONS
Connector # Color Location Fig.
C101......BK ...Front Left of Engine Compartment . .2
C102......BK ...InFront of Washer Fluid Reservoir . .2
C103......BK ...Bottom of Washer Fluid Reservoir . .2
C104......BK ...Bottom of Washer Fluid Reservoir . .2
C105......BK ...TopofWasher Fluid Reservoir.....2
C106......BK ...TopofRadiator Fan Housing......2
C107......BK ...Left Fender Side Shield.........2
C108......BK ...Left Fender Side Shield.........2
C109......BK ...Near Air Cleaner..............2
C110......BK ...Left Corner of Engine Compartment .2
C111......BK ...Rear of Intake Manifold.........4
C112......BK ...OnThrottle Body.............4
C113......BK ...OnThrottle Body.............4
C114......BK ...Rear of Intake Manifold.........4
C115......GN ...Lower Right of I.P.
C116......BK ...Near ABS Control Module
C117......GN ...Center of Dash Panel...........2
C118......BK ...Injector No. 6...............4
C119......BK ...Injector No. 5...............4
C120......BK ...Injector No. 4...............4
C121......BK ...Injector No. 3...............4
C122......BK ...Injector No. 2...............4
C123......BK ...Injector No. 1...............4
C124......BK ...OnEngine, Behind Power
Steering Pump.............4
C125......BK ...OnThermostat Housing.........4
C126......BK ...OnABSControl Module.........7
C127......BK ...Near ABS Control Module........7
C128......BK ...Near Distributor..............4
C129......BK ...Near Center of Dash Panel.......3
C130......GY ...Near Center of Dash Panel.......3
C131......BK ...Near Left Kick Panel
C132......BK ...OnSteering Column...........6
C133......BK ...Near Center of Dash Panel.......3
C134......BK ...Center of Dash Panel...........3
C135......BK ...Below Brake Master Cylinder......3
C136......BK ...Right Corner of Engine Compartment .3
C137......BK ...Right Side of Hood............3
C138......BK ...Near ABS Control Module
C139......BK ...Near ABS Control Module........7
C140......GY ...Near ABS Control Module........7
C141......GN ...Near ABS Control Module........7
C142......BK ...Right Fender Side Shield........3
C143......BK ...Right Fender Side Shield........3
C144......BK ...Right Fender Side Shield........3
C145......BK ...Right Fender Side Shield........3
C146......BK ...Below Battery................3
C147......BK ...Rear of Battery...............5
C148......BK ...AtStarter Motor..............4
C149......BK ...Right Side of Engine Near Distributor .4
C150......BK ...Rear of Generator.............4
C151......BK ...Rear of Generator.............5Connector # Color Location Fig.
C152......BK ...Behind Lens................1
C153......BK ...Left Rear of Radiator Closure Panel .1
C154......BK ...Behind Lens................1
C155......BK ...Behind Lens................1
C156......BK ...Behind Lens................1
C157......BK ...Center of Grille Opening.........1
C158......BK ...Center of Grille Opening.........1
C159......BK ...Behind Lens................1
C160......BK ...Behind Lens................1
C201......GY ...Center Bottom of I.P............8
C202......WT ...Center Bottom of I.P............8
C203......BK ...Behind Right Kick Panel........12
C204......BK ...Right Side of I.P.
C205......BK ...Left Rear of I.P...............8
C206......BK ...Left Rear of I.P...............8
C207......BK ...Near Right Kick Panel..........7
C208......GN ...Near Right Kick Panel..........7
C209......RD ...Behind Right Kick Panel........12
C210......BK ...Behind Fender Side Shield
C211......BK ...Near Right Kick Panel..........7
C212......BK ...Near Right Kick Panel
C213......BK ...Rear of Headlamp Switch.......10
C214......BK ...Rear of I.P., Right of Steering
Column..................9
C215......BK ...Rear of I.P., Right of Steering
Column..................9
C216......BK ...Rear of I.P., Right of Steering
Column.................9
C217......RD ...Rear of I.P., Right of Steering
Column..................9
C218......BK ...Below Stop Lamp Switch........7
C219......BK ...Rear of I.P., Right of Steering
Column.................9
C220......NAT ..Rear of I.P. Cluster...........10
C221......BK ...Rear of I.P. Cluster...........10
C222......NAT ..Rear of I.P., Left of Steering Column .9
C223......BK ...Rear of I.P., Left of Steering Column .9
C224......BK ...Rear of I.P., Left of Steering Column .9
C225......BK ...Rear of I.P., Left of Steering Column .9
C226......BK ...OnSteering Column...........6
C227......BK ...Near ABS Control Module........7
C228......WT ...Center of I.P.
C229......BK ...Center of I.P.
C230......BK ...OnSteering Column...........6
C231......BK ...OnSteering Column...........6
C232......BK ...OnSteering Column...........6
C233......BK ...Center Bottom of I.P............8
C234......BK ...Rear of I.P., Above Ash Receiver . . .8
C235......BK ...Rear of Radio...............9
C236......BR ...Rear of A/C-Heater Controls.....10
C237......BK ...Center Bottom of I.P............8
C238......BK ...Near ABS Control Module........7
J8W-90 CONNECTOR LOCATIONSÐXJ-RHD 8W - 90 - 1

ENGINE DIAGNOSIS
Engine diagnosis is helpful in determining the
causes of malfunctions not detected and remedied by
routine tune-ups.
These malfunctions may be classified as either per-
formance (e.g., engine idles rough and stalls) or me-
chanical (e.g., a strange noise).
Refer to the Service DiagnosisÐPerformance chart
and the Service DiagnosisÐMechanical chart for pos-
sible causes and corrections of malfunctions. Refer to
Group 14, Fuel System for the fuel system diagnosis.
GENERAL INFORMATION
Additional tests and diagnostic procedures may be
necessary for specific engine malfunctions that can
not be isolated with the Service Diagnosis charts. In-
formation concerning additional tests and diagnosis
is provided within the following diagnosis:
²Cylinder Compression Pressure Test.
²Cylinder Combustion Pressure Leakage Test.
²Engine Cylinder Head Gasket Failure Diagnosis.
²Intake Manifold Leakage Diagnosis.
INTAKE MANIFOLD LEAKAGE DIAGNOSIS
An intake manifold air leak is characterized by
lower than normal manifold vacuum. Also, one or
more cylinders may not be functioning.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A DI-
RECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR THE FAN.
DO NOT WEAR LOOSE CLOTHING.
METHOD 1
(1) Start the engine.
(2) Spray a small stream of water at the suspected
leak area.
(3) If a change in RPM'S, the area of the suspected
leak has been found.
(4) Repair as required.
CYLINDER COMPRESSION PRESSURE TEST
The results of a cylinder compression pressure test
can be utilized to diagnose several engine malfunc-
tions.
Ensure the battery is completely charged and the
engine starter motor is in good operating condition.
Otherwise the indicated compression pressures may
not be valid for diagnosis purposes.
(1) Clean the spark plug recesses with compressed
air.
(2) Remove the spark plugs.
(3) Secure the throttle in the wide-open position.
(4) Disconnect the ignition coil.(5) Insert a compression pressure gauge and rotate
the engine with the engine starter motor for three
revolutions.
(6) Record the compression pressure on the 3rd
revolution. Continue the test for the remaining cylin-
ders.
Refer to Engine Specifications for the correct en-
gine compression pressures.
ENGINE CYLINDER HEAD GASKET FAILURE
DIAGNOSIS
A leaking engine cylinder head gasket usually re-
sults in loss of power, loss of coolant and engine mis-
firing.
An engine cylinder head gasket leak can be located
between adjacent cylinders or between a cylinder and
the adjacent water jacket.
²An engine cylinder head gasket leaking between
adjacent cylinders is indicated by a loss of power
and/or engine misfire.
²An engine cylinder head gasket leaking between a
cylinder and an adjacent water jacket is indicated by
coolant foaming or overheating and loss of coolant.
CYLINDER-TO-CYLINDER LEAKAGE TEST
To determine if an engine cylinder head gasket is
leaking between adjacent cylinders; follow the proce-
dures outlined in Cylinder Compression Pressure
Test. An engine cylinder head gasket leaking between
adjacent cylinders will result in approximately a 50-
70% reduction in compression pressure.
CYLINDER-TO-WATER JACKET LEAKAGE
TEST
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A DI-
RECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR THE FAN.
DO NOT WEAR LOOSE CLOTHING.
Remove the radiator cap.
Start the engine and allow it to warm up until the
engine thermostat opens.
If a large combustion/compression pressure leak ex-
ists, bubbles will be visible in the coolant.
If bubbles are not visible, install a radiator pres-
sure tester and pressurize the coolant system.
If a cylinder is leaking combustion pressure into
the water jacket, the tester pointer will pulsate with
every combustion stroke of the cylinder.
JENGINES 9 - 5

(7) Disconnect the wires at the starter motor sole-
noid and injection wire harness connector.
(8) Disconnect the quick-connect fuel lines at the
fuel rail and return line by squeezing the two retain-
ing tabs against the fuel tube (Fig. 20). Pull the fuel
tube and retainer from the quick-connect fitting (re-
fer to Group 14, Fuel System for the proper proce-
dure).
(9) Remove the fuel line bracket from the intake
manifold.
(10) Disconnect the engine ground strap.
(11) Remove the air cleaner assembly.
(12) Disconnect the vacuum purge hose at the fuel
vapor canister tee.
(13) Disconnect the idle speed actuator wire con-
nector.
(14) Disconnect the throttle cable and remove it
from the bracket.
(15) Disconnect the throttle rod at the bellcrank.
(16) Disconnect the speed control cable, if
equipped.
(17) Disconnect the oxygen sensor wire connector.
(18) Disconnect the upper and lower radiator hoses
at the radiator.
(19) Disconnect the coolant hoses from the rear of
the intake manifold and thermostat housing.
(20) Disconnect the heater hoses.
(21) Remove the fan shroud screws.
(22) Remove the radiator attaching bolts.
(23) Remove the radiator and fan shroud.
(24) Remove the fan and spacer or Tempatrol fan
assembly.
(25) Install a 5/16 X 1/2-inch SAE capscrew
through fan pulley into water pump flange. This will
maintain the pulley and water pump in alignment
when crankshaft is rotated.
(26) Remove the power brake vacuum check valve
from the booster, if equipped.
(27) If equipped with power steering:(a) Disconnect the hoses from the fittings at the
steering gear.
(b) Drain the pump reservoir.
(c) Cap the fittings on the hoses and steering
gear to prevent foreign objects from entering the
system.
(28) Lift the vehicle and support it with support
stands.
(29) Remove the oil filter.
(30) Remove the starter motor.
(31) Remove the flywheel housing access cover.
(32) Remove the engine support cushion-to-bracket
through bolts.
(33) Disconnect the exhaust pipe from the mani-
fold.
(34) Remove the upper flywheel housing bolts and
loosen the bottom bolts.
(35) Remove the engine shock damper bracket
from the sill.
(36) Lower the vehicle.
(37) Attach a lifting device to the engine.
(38) Raise the engine off the front supports.
(39) Place a support stand under the flywheel
housing.
(40) Remove the remaining flywheel housing bolts.
(41) Lift the engine out of the engine compartment
and install on an engine stand.
(42) Install the oil filter to keep foreign material
out of the engine.
INSTALLATION
(1) Remove the oil filter.
(2) Lift the engine off the stand and lower it into
the engine compartment. For easier installation, it
may be useful to remove the engine support cushions
from the engine support brackets as an aide for
alignment of the engine-to-transmission.
(3) Insert the transmission shaft into the clutch
spline.
(4) Align the flywheel housing with the engine.
(5) Install and finger tighten the flywheel housing
lower bolts.
(6) Install the engine support cushions (if re-
moved).
(7) Remove the support stand from beneath the
flywheel housing.
(8) Lower the engine and engine support cushions
onto the engine compartment brackets. Ensure that
the bolt holes are aligned. Install the bolts and
tighten.
(9) Remove the engine lifting device.
(10) Raise the vehicle.
(11) Attach the engine shock damper bracket to
the sill.
(12) Attach the exhaust pipe to the manifold. In-
stall and tighten the nuts to 31 Nzm (23 ft. lbs.)
torque.
(13) Install the flywheel housing access cover.
Fig. 20 Fuel Line Quick-Connect Couplings
J2.5L ENGINE 9 - 21