1988 JEEP CHEROKEE engine coolant

EN G IN E C O OLIN G F A N

1988 J e ep C hero ke e
1987-88 ENGINE COOLING
Thermostatically Controlled Electric Fans
Cherokee, Comanche, Wagoneer
DESCRIPTION & OPERATION
On Cherokee, Comanche and Wagoneer models with a 4.0L engine,
A/C and/or heavy duty cooling system, an auxiliary electric fan is
used. The auxiliary fan is controlled by a relay mounted on the left
inner fender panel. A radiator temperature switch attached to the
radiator outlet tank above the lower radiator hose senses engine
coolant temperature.
When coolant temperature is more than 190(0)F (88(0)C), t\
he
radiator coolant temperature switch closes allowing current from the
ignition switch to flow through the fan relay to ground activating the
relay. When relay is activated, battery voltage is supplied to the fan
causing it to operate. When coolant temperature is below 190(0)F
(88(0)C), the radiator coolant temperature switch opens preventing t\
he
relay from being grounded and electric cooling fan from being
energized.
When the A/C (if equipped) is turned on, the Electronic
Control Unit (ECU) grounds the A/C relay coil allowing current to flow\
through it. This activates the A/C relay which then supplies current
to the A/C clutch, fan diode assembly and cooling fan relay. The
cooling fan relay is activated and the fan operates. Whenever the A/C
is used, regardless of engine coolant temperature, the auxiliary
electric cooling fan operates.
TESTING
NOTE: For following tests, refer to fan relay connector terminal
identification and fan controls identification. See Figs. 1
and 2.
With Air Conditioning
1) If electric cooling fan does not work all the time, go to
step 3). If electric cooling fan is inoperative when A/C compressor
operates, start engine and turn A/C on. Disconnect fan relay
connector. Fan relay is located on left inner fender panel.
2) Using a voltmeter, check for voltage at fan relay
connector terminal No. 2. If voltmeter does not read battery voltage,
replace fan diode assembly.
3) Disconnect fan relay connector. Fan relay is located on
left inner fender panel. Using a jumper wire with an in-line 25-amp
fuse, supply battery voltage to fan relay connector terminal No. 4.
4) If fan operates, motor is okay. Go to next step. If fan
motor does not operate, check continuity between fan relay connector
terminal No. 4 and body ground connections. If continuity exists,
replace fan motor. If continuity does not exist, repair open and
retest.
5) Disconnect fan relay connector. Turn ignition switch to
the "RUN" position. Check continuity between fan relay connector
terminal No. 5 and body ground connections. If continuity does not
exist, repair open circuit. If continuity exists, go to next step.
6) Using a jumper wire with an in-line 25-amp fuse, jump
across fan relay connector terminals No. 1 and No. 4. If fan motor
operates, go to next step. If fan motor does not operate, repair fan

Engine pre-oiling can be done using pressure oiler (if
available). Connect pressure oiler to cylinder block oil passage
such as oil pressure sending unit. Operate pressure oiler long enough
to ensure correct amount of oil has filled crankcase. Check oil level
while pre-oiling.
If pressure oiler is not available, disconnect ignition
system. Remove oil pressure sending unit and replace with oil pressure
test gauge. Using starter motor, rotate engine starter until gauge
shows normal oil pressure for several seconds. DO NOT crank engine
for more than 30 seconds to avoid starter motor damage.
Ensure oil pressure has reached the most distant point from
the oil pump. Reinstall oil pressure sending unit. Reconnect ignition
system.
INITIAL START-UP
Start the engine and operate engine at low speed while
checking for coolant, fuel and oil leaks. Stop engine. Recheck coolant
and oil level. Adjust if necessary.
CAMSHAFT
Break-in procedure is required when a new or reground
camshaft has been installed. Operate and maintain engine speed between
1500-2500 RPM for approximately 30 minutes. Procedure may vary due to
manufacturers recommendations.
PISTON RINGS
Piston rings require a break-in procedure to ensure seating
of rings to cylinder walls. Serious damage may occur to rings if
correct procedures are not followed.
Extremely high piston ring temperatures are produced obtained
during break-in process. If rings are exposed to excessively high RPM
or high cylinder pressures, ring damage can occur. Follow piston ring
manufacturer's recommended break-in procedure.
FINAL ADJUSTMENTS
Check or adjust ignition timing and dwell (if applicable).
Adjust valves (if necessary). Adjust carburetion or injection idle
speed and mixture. Retighten cylinder heads (if required). If
cylinder head or block is aluminum, retighten bolts when engine is
cold. Follow the engine manufacturer's recommended break-in procedure
and maintenance schedule for new engines.
NOTE: Some manufacturer's require that head bolts be retightened
after specified amount of operation. This must be done to
prevent head gasket failure.

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EN G IN E R EM OVA L - 4 -C YL

1988 J e ep C hero ke e
1988 ENGINES
Jeep - Engine Removal - 4-Cylinder
Cherokee, Comanche, Wrangler
4-CYLINDER ENGINES
2.5L
1) Disconnect negative battery cable. Drain cooling system.
Remove air cleaner, lower radiator hose, fan shroud, and engine
compartment light from hood. Scribe hinge locations and remove hood.
Disconnect automatic transmission cooler lines at radiator (if
equipped).
2) Remove upper radiator hose, fan assembly and coolant
recovery hose. Remove radiator and A/C condenser (if equipped). Hold
fan pulley to water pump flange using 5/16" x 1/2" SAE capscrew.
Disconnect heater hoses, throttle linkages, cruise control cable (if
equipped) and Throttle valve rod.
3) Disconnect wires from starter and separate CEC system
wiring harness connector. Disconnect fuel pipe from fuel pump and fuel
return hose from fuel filter. Disconnect hoses from A/C compressor and
power steering pump (if equipped). Drain power steering pump
reservoir. Cap all fittings and hose ends.
4) Remove vacuum check valve from brake booster (if
equipped). Tag and remove all wiring and vacuum lines connected to
engine or accessories. Raise vehicle and remove starter. Disconnect
exhaust pipe from manifold.
5) Remove converter/flywheel housing cover. Remove engine
mount nuts at bracket side. On automatic transmission models, index
mark drive plate and torque converter. Remove drive plate-to-converter
bolts.
6) Remove upper and loosen lower bellhousing-to-engine bolts.
Attach lifting equipment to engine. Raise engine off front mounts,
Place support under bellhousing. Remove remaining bellhousing-to-
engine bolts. Lift engine out of engine compartment.
NOTE: Engine mount pads may be removed from engine brackets to
align engine and transmission during installation.
TORQUE SPECIFICATIONS
TORQUE SPECIFICATIONS TABLE








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Application Ft. Lbs. (N.m)
Clutch Housing-to-Block Bolts .................... 55 (75)
Drive Plate-to-Converter ......................... 26 (35)
Flywheel Bolts ............................... ( 1) 50 (68)
Front Support Bracket-to-Block ................... 45 (61)
Front Support Cushion-to-Crossmember ............. 33 (45)
Rear Support Bracket-to-Transmission ............. 33 (45)
Rear Support Cushion-to-Bracket .................. 30 (41)
Starter Motor-to-Block ........................... 33 (45)
( 1) - Tighten an additional 60 degrees.









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CLUTCH PEDAL POSITION SWITCHES
COLD START INJECTORS
CONNECTORS
COOLANT
COOLANT RECOVERY TANKS
COOLING FAN MOTOR MODULES
COOLING FAN MOTOR RELAYS AND MODULES
COOLING FAN MOTOR RESISTORS
COOLING FAN MOTOR SENSORS AND SWITCHES
COOLING FAN MOTOR SWITCHES
COOLING FAN MOTORS
CRANKSHAFT POSITION SENSORS
DECEL VALVES
DEFLECTORS
DIP STICKS AND TUBES
DIP STICK TUBES
DISTRIBUTOR ADVANCES AND RETARDERS (MECHANICAL AND VACUUM)
DISTRIBUTOR BOOTS AND SHIELDS
DISTRIBUTOR CAPS
DISTRIBUTOR RETARDERS (MECHANICAL AND VACUUM)
DISTRIBUTOR ROTORS
DISTRIBUTOR SHIELDS
DISTRIBUTORS
EARLY FUEL EVAPORATION VALVES (HEAT RISER ASSEMBLIES)
EGR COOLERS
EGR EXHAUST MANIFOLD PASSAGES
EGR INTAKE AND EXHAUST MANIFOLD PASSAGES
EGR PLATES AND COOLERS
ELECTRONIC SPARK CONTROL MODULES
ELECTRONIC TRANSMISSION CONTROL DEVICES
ELECTRONIC TRANSMISSION FEEDBACK DEVICES
ENGINE COOLANT TEMPERATURE SENSORS
ENGINE COOLING SYSTEMS
ENGINE COVERS (OIL PAN, VALVE COVER, TIMING COVER)
ENGINE OIL
ENGINE OIL CANISTERS
ENGINE OIL COOLERS (EXTERNAL)
ENGINE OIL DRAIN PLUGS AND GASKETS
ENGINE OIL FILTERS AND CANISTERS
ENGINE OIL GASKETS
ENGINE OIL PRESSURE GAUGES (MECHANICAL)
EVAPORATIVE EMISSION (EVAP) CANISTER FILTERS
EVAPORATIVE EMISSION (EVAP) CANISTER PURGE DEVICES
EVAPORATIVE EMISSION (EVAP) CANISTERS
EVAPORATIVE EMISSION (EVAP) FEEDBACK DEVICES
EXHAUST GAS RECIRCULATION DEVICES
EXHAUST GAS RECIRCULATION FEEDBACK DEVICES
EXPANSION PLUGS
FAN CONTROL SENSORS
FUEL
FUEL ACCUMULATORS AND DAMPERS
FUEL AND COLD START INJECTORS
FUEL DAMPERS
FUEL DELIVERY CHECK VALVES
FUEL DISTRIBUTORS (BOSCH CIS)
FUEL FILLER NECKS AND RESTRICTORS
FUEL FILTERS
FUEL INJECTORS
FUEL LEVEL SENDERS7
FUEL PRESSURE REGULATORS
FUEL PUMPS (IN-TANK AND EXTERNAL, ELECTRICAL OR MECHANICAL)
FUEL RAILS
FUEL RESTRICTORS

Reasons to Suggest Repair or Replacement
1 - Part is close to the end of its useful life (just above
discard specifications, or weak; failure likely to occur
soon, etc.)
2 - To address a customer need, convenience, or request (to
stiffen ride, enhance performance, eliminate noise,
etc.)
3 - To comply with maintenance recommended by the vehicle's
Original Equipment Manufacturer (OEM)
4 - Technician's recommendation based on substantial and
informed experience
NOTE: Suggested services are always optional. When presenting
suggested repairs to the customer, you must present the
facts, allowing the customer to draw their own conclusions
and make an informed decision about how to proceed.
ENGINE ASSEMBLIES
SERVICE PROCEDURES REQUIRED AND SUGGESTED FOR PROPER VEHICLE
OPERATION
CYLINDER HEAD ASSEMBLIES
NOTE: A Cylinder Head Assembly is a cylinder head fitted with
valves, associated springs, retainers, and on overhead
camshaft cylinder heads (OHC), camshaft, camshaft
bearings, lash adjusters, tappets and rockers.
CYLINDER HEAD ASSEMBLY INSPECTION









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Condition Code Procedure
Adjustable valve lash is
out of specification ... B ................. Require repair.
Internal component failure
(any component) ........ A ........... ( 1) Require repair or
replacement of cylinder
head assembly.
( 1) - It is Required that all other failure related components
be inspected for cause and condition. Additional components
or assemblies may be Suggested for repair or replacement,
such as a water pump on a short block (reason code 4,
technician's recommendation based on substantial and
informed experience).
Example:
If there is a failed head gasket with an external coolant
leak, in addition to Requiring replacement of the head
gasket, inspection of the following for cause and condition
is Required: Block, Cooling System, Cylinder Head. It may
be Suggested that additional inspections be performed, such
as the other head gasket on a V-type engine.









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LONG BLOCK ASSEMBLIES
NOTE: A Long Block Assembly is a short block assembly together
with a cylinder head assembly and all those components
fitted within the rocker or cam cover, and timing cover

(the whole presented as an assembly). A rebuilt or new
oil pump, or kit shall be supplied or fitted as
appropriate.
LONG BLOCK ASSEMBLY INSPECTION









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Condition Code Procedure
Internal component failure
(any component) ........ A ........... (1) Require repair or
replacement of the long
block assembly.
( 1) - It is Required that all other failure related components
be inspected for cause and condition. Additional components
or assemblies may be Suggested for repair or replacement
such as a water pump on a short block (reason code 4,
technician's recommendation based on substantial and
informed experience).
Example:
If there is a failed head gasket with an external coolant
leak, in addition to Requiring replacement of the head
gasket, inspection of the following for cause and
condition is Required: Block, Cooling System, Cylinder
Head. It may be Suggested that additional inspections be
performed, such as the other head gasket on a V-type
engine.









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SHORT BLOCK ASSEMBLIES
NOTE: A Short Block Assembly is a cylinder block and all those
components contained within the limits of the block deck
or decks, the pan rail, the block rear face and the
timing cover (where fitted), including the crankshaft.
SHORT BLOCK ASSEMBLY INSPECTION









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Condition Code Procedure
Any internal component
failure ................ A ........... ( 1) Require repair or
replacement of the short
block assembly.
( 1) - It is Required that all other failure related components
be inspected for cause and condition. Additional
components or assemblies may be Suggested for repair or
replacement, such as a water pump on a short block
(reason code 4, technician's recommendation based on
substantial and informed experience).
Example:
If there is a failed head gasket with an external coolant
leak, in addition to Requiring replacement of the head
gasket, inspection of the following for cause and condition
is Required: Block, Cooling System, Cylinder Head. It may
be Suggested that additional inspections be performed,
such as the other head gasket on a V-type engine.









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Attaching hardware
threads stripped
(threads missing) ...... A ... Require repair or replacement
of hardware.
Connector broken ........ A .. Require repair or replacement.
Connector (Weatherpack
type) leaking .......... A .. Require repair or replacement.
Connector melted ........ A ........... (1) Require repair or
replacement.
Connector missing ....... C ............ Require replacement.
Contaminated ............ A ........... ( 2) Require repair or
replacement.
Inoperative ............. B ........... ( 3) Require repair or
replacement. Further
inspection required.
Leaking ................. A .. Require repair or replacement.
Missing ................. C ............ Require replacement.
Resistance out of
specification ........... B .. Require repair or replacement.
Restricted, affecting
performance ............ A .. Require repair or replacement.
Terminal broken ......... A .. Require repair or replacement.
Terminal burned, affecting
performance ............ A ........... ( 1) Require repair or
replacement.
Terminal burned, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal corroded,
affecting performance .. A .. Require repair or replacement.
Terminal corroded, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal loose, affecting
performance ............ B .. Require repair or replacement.
Terminal loose, not
affecting performance .. 1 .. Suggest repair or replacement.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.
Wire lead conductors
exposed ................ B .. Require repair or replacement.
Wire lead corroded ...... A .. Require repair or replacement.
Wire lead open .......... A .. Require repair or replacement.
Wire lead shorted ....... A .. Require repair or replacement.
( 1) - Determine cause and correct prior to repair or
replacement of part.
( 2) - Determine source of contamination, such as engine
coolant, fuel, metal particles, or water. Require
repair or replacement.
( 3) - Inoperative includes intermittent operation or out of OEM
specification. Some components may be serviceable; check
for accepted cleaning procedure.









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AIR CONDITIONING PRESSURE SENSORS
AIR CONDITIONING PRESSURE SENSOR INSPECTION








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Condition Code Procedure
Attaching hardware
missing ................ C .......... Require replacement of
hardware.

Attaching hardware
threads damaged ........ A ... Require repair or replacement
of hardware.
Attaching hardware
threads stripped
(threads missing) ...... A ... Require repair or replacement
of hardware.
Connector broken ........ A .. Require repair or replacement.
Connector (Weatherpack
type) leaking .......... A .. Require repair or replacement.
Connector melted ........ A ........... (1) Require repair or
replacement.
Connector missing ....... C ............ Require replacement.
Contaminated ............ A ........... ( 2) Require repair or
replacement.
Inoperative ............. B ........... ( 3) Require repair or
replacement. Further
inspection required.
Leaking ................. A .. Require repair or replacement.
Missing ................. C ............ Require replacement.
Resistance out of
specification .......... B .. Require repair or replacement.
Restricted, affecting
performance ............ A .. Require repair or replacement.
Terminal broken ......... A .. Require repair or replacement.
Terminal burned, affecting
performance ............ A ........... ( 1) Require repair or
replacement.
Terminal burned, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal corroded,
affecting performance .. A .. Require repair or replacement.
Terminal corroded, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal loose, affecting
performance ............ B .. Require repair or replacement.
Terminal loose, not
affecting performance .. 1 .. Suggest repair or replacement.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.
Wire lead conductors
exposed ................ B .. Require repair or replacement.
Wire lead corroded ...... A .. Require repair or replacement.
Wire lead open .......... A .. Require repair or replacement.
Wire lead shorted ....... A .. Require repair or replacement.
( 1) - Determine cause and correct prior to repair or
replacement of part.
( 2) - Determine source of contamination, such as engine
coolant, fuel, metal particles, or water. Require
repair or replacement.
( 3) - Inoperative includes intermittent operation or out of
OEM specification. Some components may be serviceable;
check for accepted cleaning procedure.









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AIR DUCTS AND TUBES
AIR DUCT AND TUBE INSPECTION








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Condition Code Procedure