1988 JEEP CHEROKEE cooling

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2.5 L 4 -C YL - V IN [ H ]

1 988 J e ep C hero ke e
1988 CHRYSLER MOTORS ENGINES
2.5L 4-Cylinder
Jeep: Cherokee, Comanche, Wagoneer, Wrangler
ENGINE CODING
ENGINE IDENTIFICATION
NOTE: For engine repair procedures not covered in this article,
see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article
in the GENERAL INFORMATION section.
The Vehicle Identification Number (VIN) is located on the
upper left side of dash, visible through windshield. The fourth
character of the VIN identifies the engine size. The tenth character
identifies the model year.
ENGINE IDENTIFICATION CODES TABLE









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Application VIN Code
2.5L 4-Cylinder TBI .................................... H









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SPECIAL ENGINE MARKS
Some engines are produced at the factory with oversize or
undersize components. These engines are identified by a letter code
stamped between ignition coil and distributor. Letters are decoded as
follows:
* "B" indicates all cylinder bores .010" (.25 mm) oversize.
* "C" indicates all camshaft bearing bores .010" (.25 mm)
oversize.
* "M" indicates all main bearing journals .010" (.25 mm)
undersize.
* "P" indicates all connecting rod journals .010" (.25 mm)
undersize.
REMOVAL & INSTALLATION
ENGINE REMOVAL
See ENGINE REMOVAL article.
INTAKE & EXHAUST MANIFOLDS
NOTE: Throttle body removal is necessary prior to manifold
removal. Throttle body can be separated from the manifold
and secured in a designated area with vacuum hoses attached.
Removal
1) Disconnect negative battery cable. Remove air cleaner, EGR
pipe and PCV hose. Disconnect and mark all vacuum hoses and electrical
connections. Drain cooling system.
2) Remove coolant hoses from intake manifold. Remove A/C
compressor and power steering pump and mounting bracket (if equipped).\

Disconnect throttle valve linkage on A/T models.
3) Remove coolant temperature sensor wire. Disconnect
throttle cable at bellcrank. Remove intake manifold bolts. Remove
intake manifold.
4) If exhaust manifold requires removal, raise and support
vehicle. Disconnect exhaust pipe. Remove oxygen sensor wire and remove
sensor. Remove manifold-to-cylinder head bolts. Remove exhaust
manifold.
Installation
1) Ensure all gasket surfaces are clean. Install manifolds
and gasket on cylinder head. Start all bolts and finger tighten.
Tighten bolts in proper sequence. See Fig. 1. Tighten bolts to
specification. See TORQUE SPECIFICATIONS table.
2) Clean oxygen sensor threads. Apply anti-seize on oxygen
sensor threads prior to installation. Install sensor and tighten to
specification. Reverse removal procedures to complete installation.
Fill and purge cooling system. See COOLING SYSTEM AIR PURGE under
ENGINE COOLING.
Fig. 1: Manifold Bolt Tightening Sequence
CYLINDER HEAD
Removal
1) Disconnect negative battery cable. Drain cooling system.
Remove air cleaner. Remove intake and exhaust manifolds. See INTAKE &
EXHAUST MANIFOLDS.
2) Disconnect and mark all hoses and electrical connections
at cylinder head. Disconnect and mark spark plug wires. Remove spark
plugs. Remove valve cover bolts.

3) Remove rocker arms and push rods. See ROCKER ARMS &
BRIDGE under VALVES. Remove cylinder head bolts. Remove cylinder head.
Inspection
Inspect cylinder head for cracks or damage. Using
straightedge, check cylinder head for warpage in several areas. Repair
or replace cylinder head if warpage exceeds .002" (.05 mm) per each 6"\
(152 mm) or damage exists.
Installation
1) Ensure all gasket surfaces are clean. Clean carbon from
combustion chambers and tops of pistons. Apply sealant to both sides
of new cylinder head gasket. Install new gasket with the word "TOP"
upward. Ensure all holes are aligned.
2) Install cylinder head. Apply sealing compound to threads
of cylinder head bolt No. 8 prior to installation. See Fig. 2. Install
head bolts. Tighten all bolts in sequence (except No. 8) to 110 ft.
lbs. (149 N.m). Tighten No. 8 head bolt to 100 ft. lbs. (136 N.m). S\
ee
Fig. 2 .
3) Reverse removal procedures for remaining components. When
installing valve cover, use RTV sealant between cover and head.
Tighten bolts to specification.
4) Fill cooling system with temperature sending unit removed.
Allow trapped air to escape, then install sending unit. Refill and
purge cooling system. See COOLING SYSTEM AIR PURGE under ENGINE
COOLING.
Fig. 2: Cylinder Head Bolt Tightening Sequence
VALVES
Valve Arrangement
E-I-I-E-E-I-I-E (Front-to-rear).
Valve Guides
Valve guides are not replaceable. If clearance is excessive,
valve guides must be reamed to accommodate oversized stem valves.
ROCKER ARMS & BRIDGE

specification. Install front cover oil seal. See FRONT COVER OIL SEAL
Remove front cover seal installer.
4) Reverse removal procedures. Lubricate vibration damper
retaining bolt with oil prior to installation. Tighten bolts to
specification.
FRONT COVER OIL SEAL
Removal & Installation
1) Remove vibration damper. Using Seal Remover (J-9256),
remove seal from front cover. Position new seal on Front Cover Seal
Installer (J-22248) with lip facing outward.
2) Apply sealant to seal outer diameter. Lightly coat
crankshaft with oil. Place front cover seal installer on front of
crankshaft. Tap seal into front cover. Remove seal installer. Lightly
coat seal contact area of vibration damper with oil.
3) Install key in crankshaft (if removed). Install vibration\
damper. Lubricate vibration damper bolt with oil. Install retaining
bolt and washer. Tighten to specification.
CAMSHAFT & TIMING GEAR
Removal
1) Drain cooling system. Remove radiator. Remove engine front
cover. See ENGINE FRONT COVER. Remove distributor. Remove fuel pump
(if equipped with mechanical pump). Remove rocker arms and pushrods.
See ROCKER ARMS & BRIDGE under VALVES.
2) Remove valve lifters. Mark lifters for location. Remove
crankshaft oil slinger. Pull chain tensioner block toward tensioner
lever to compress spring. Hold block and move tensioner lever to lock
position. See Fig. 3.
3) Rotate crankshaft and align timing marks on crankshaft and
camshaft gears. Remove camshaft gear retaining bolt. Remove gears and
timing chain. Remove camshaft.
Fig. 3: Location of Chain Tensioner Lock
Courtesy of Chrysler Motors.
Inspection
Inspect camshaft for flaking, lobe wear or worn bearing

1) Drain cooling system. Remove fan shroud and drive belts.
Remove fan assembly.
2) Disconnect heater hoses and lower radiator hose at water
pump. Remove water pump retaining bolts. Remove water pump.
Installation
Clean all gasket surfaces. Install water pump. Tighten bolts
to specification. Ensure pump turns freely. Reverse removal
procedures. Fill and purge air from cooling system.
NOTE: It may be necessary to remove heater hose to remove trapped
air if system cannot be purged using following procedures.
Cooling System Air Purge (Vehicles With Coolant Recovery)
Fill system to proper level. Place heater control to "HEAT"
position and temperature control to "WARM" or "HIGH" position. Install
coolant caps. Operate engine to normal operating temperature. Shut off
engine and allow system to cool. Add coolant to recovery bottle.
Repeat procedure to obtain correct coolant level.
Cooling System Air Purge (Vehicles Without Coolant Recovery)
Fill system to proper level. Place heater control to "HEAT"
position and temperature control to "WARM" or "HIGH" position. Operate
engine to normal operating temperature with radiator cap removed. Add
necessary coolant and install radiator cap.
NOTE: For further information on cooling system capacities and
other cooling system components, see ENGINE COOLING SYSTEMS
article.
ENGINE OILING
CRANKCASE CAPACITY
Crankcase capacity is 4 qts. (3.8 L) with oil filter change.
NORMAL OIL PRESSURE
Normal oil pressure should be 13 psi (.91 kg/cm) at 600 RPM
or 37-75 psi (2.6-5.3 kg/cm) at 1600 RPM.
OIL PRESSURE REGULATOR VALVE
Oil pressure regulator valve is located in oil pump body and
is nonadjustable.
OILING SYSTEM
Engine lubrication is provided by the distributor driven
gear-type oil pump. Oil is supplied through the full-flow oil filter
and into an internal oil passage. Internal passage runs along right
side of block and intersects lifter bores.
Oil is then routed to camshaft and crankshaft bearings. Oil
is supplied to rocker arms from the hydraulic lifters and through the
push rods. By-pass valves are located in oil filter mounting and oil
pump.
OIL PUMP
Removal
Remove oil pan. See OIL PAN REMOVAL article. Remove oil pump

nuts. Install motor and WOT switch bracket assembly on throttle body.
2) Connect wiring harness connector to ISA motor and WOT
switch. Connect the throttle return spring, throttle cable and cruise
control cable. Adjust ISA motor and WOT switch. Install air cleaner
assembly.
NOTE: After replacing or reinstalling the original ISA motor, be
sure motor plunger is fully extended before starting the
engine. If plunger is not fully extended, the closed
throttle switch may open prematurely, causing idle speed to
drop to approximately 400 RPM.
3) Start engine with throttle at 1/4 open position. This
prevents ISA plunger from retracting. Stop engine. When ignition is
turned off, the motor plunger will fully extend. After installation
is complete, adjust ISA as required.
ELECTRONIC CONTROL UNIT
Removal & Installation
Locate ECU in passenger compartment, below glove box. Remove
retaining screws and mounting bracket. Remove the ECU, and disconnect
wiring harness connector from ECU. Reverse removal procedure to
install.
OXYGEN SENSOR
Removal
Disconnect the wire connector from sensor, and unscrew
sensor from exhaust pipe adapter. Clean adapter threads.
Installation
1) Apply anti-seize compound to sensor threads. Do not allow
compound to adhere to any other part of sensor. Hand start the sensor
into place and tighten. Check that wire terminal ends are properly
seated in connector. Connect wire.
2) Do not push the rubber boot over sensor body lower than
1/2" (13 mm) above base of sensor. If the sensor wire should break,
sensor must be replaced. These wires cannot be spliced or otherwise
repaired.
MANIFOLD AIR TEMPERATURE & MANIFOLD ABSOLUTE PRESSURE SENSORS
Removal & Installation
Disconnect wiring harness connector from sensor. Disconnect
vacuum hose from MAP sensor. Remove sensor. Clean MAT sensor manifold
threads, and wrap with Teflon tape. To install, reverse removal
procedure.
COOLANT TEMPERATURE SENSOR (CTS)
Removal & Installation
Allow engine to cool and release pressure from cooling
system. Remove wiring harness from sensor. Remove sensor at rear of
intake manifold, and plug hole to prevent excessive coolant loss. To
install, reverse removal procedure and replace lost coolant.
EGR VALVE & CANISTER PURGE SOLENOID
Removal & Installation
Disconnect wiring harness and vacuum hose from solenoid.
Remove solenoid and bracket as an assembly. Replace solenoid as an

from intake manifold. Disconnect fuel lines at fuel rail. Fuel lines
are removed by squeezing the 2 retaining tabs against the fuel line
and pulling the fuel line from the connector. Use caution as these
fuel lines are under pressure.
3) Loosen drive belt tensioner and remove drive belt. Remove
power steering pump and bracket from intake manifold. Remove fuel rail
retaining bolts. Remove fuel rail and injector assembly.
4) Remove intake manifold heat shield. Disconnect EGR tube
fittings. Disconnect exhaust pipe from manifold. Disconnect oxygen
sensor. Remove retaining bolts and remove manifolds.
Installation
1) Install new gasket. Install exhaust and intake manifolds
and loosely install bolts. Install EGR tube between manifolds. Tighten
manifold bolts in proper sequence see Fig. 1. Tighten to
specifications, see TORQUE SPECIFICATIONS TABLE in this article.
2) Tighten EGR tube bolts. Apply anti-seize to oxygen sensor
threads prior to installation. Reverse removal procedures for
remaining components. Tighten bolts to specification.
3) Install new "O" rings on fuel line connectors prior to
installation. Ensure "CLICK" sound is heard when installing fuel
lines. This indicates that fuel lines are properly seated.
Fig. 1: Manifold Tightening Sequence (4.0L)
Courtesy of Chrysler Motors.
INTAKE & EXHAUST MANIFOLD (4.2L)
Removal
1) Remove air cleaner. Disconnect fuel line at carburetor.
Mark and disconnect all vacuum hoses, ventilation hoses and electrical
connectors at intake manifold.
2) Disconnect throttle cable at bellcrank. On A/T models,
disconnect throttle valve rod. On all models, remove PCV hose from
manifold. Drain cooling system. Remove coolant hoses from intake

manifold.
3) Remove EGR tube fittings from manifolds. Remove power
steering pump and A/C compressor and mounting brackets (if equipped).
4) Remove intake manifold bolts. Remove intake manifold. If
exhaust manifold requires removal, disconnect exhaust pipe from
manifold. Remove oxygen sensor (if equipped). Remove exhaust manifold.\
Installation
1) Install new gasket. Install exhaust manifold and loosely
install bolts. Install intake manifold. Tighten bolts to specification
in proper sequence. See Fig. 2.
2) Apply anti-seize to oxygen sensor threads prior to
installation. Reverse removal procedure for remaining components.
Tighten bolts to specification. Fill and purge cooling system. See
COOLING SYSTEM AIR PURGE under WATER PUMP in this article.
Fig. 2: Manifold Tightening Sequence (4.2L)
Courtesy of Chrysler Motors.
CYLINDER HEAD
Removal
1) Disconnect negative battery cable. Drain cooling system.
Disconnect hoses at thermostat housing. Remove intake and exhaust
manifolds. See the following:
* INTAKE & EXHAUST MANIFOLD (4.0L) .
* INTAKE & EXHAUST MANIFOLD (4.2L) .
2) Disconnect and mark all hoses and electrical connections
at cylinder head. Disconnect and mark spark plug wires. Remove spark
plugs. Remove valve cover bolts.
3) Remove the rocker arms and the push rods. Remove cylinder
head bolts. Remove cylinder head. See ROCKER ARMS & BRIDGE.
Inspection
Inspect cylinder head for cracks or damage. Using
straightedge, check cylinder head for warpage in several areas. Repair