1988 JEEP CHEROKEE radiator cap

GEN ER AL C O OLIN G S YSTE M S ER VIC IN G

1988 J e ep C hero ke e
GENERAL INFORMATION
General Cooling System Servicing
* PLEASE READ THIS FIRST *
The following article is for general information only.
Information may not apply to all years, makes and models. See specific
article in the ENGINE COOLING section.
DESCRIPTION
The basic liquid cooling system consists of a radiator, water
pump, thermostat, electric or belt-driven cooling fan, pressure cap,
heater, and various connecting hoses and cooling passages in the block
and cylinder head.
MAINTENANCE
DRAINING
Remove radiator cap and open heater control valve to maximum
heat position. Open drain cocks or remove plugs in bottom of radiator
and engine block. In-line engines usually have one plug or drain cock,
while "V" type engines will have 2, one in each bank of cylinders.
CLEANING
A good cleaning compound removes most rust and scale. Follow
manufacturer's instructions in the use of cleaner. If considerable
rust and scale has to be removed, cooling system should be flushed.
Clean radiator air passages with compressed air.
FLUSHING
CAUTION: Some manufacturers use an aluminum and plastic radiator.
Flushing solution must be compatible with aluminum.
Back Flushing
Back flushing is an effective means of removing cooling
system rust and scale. The radiator, engine and heater core should be
flushed separately.
Radiator
To flush radiator, connect flushing gun to water outlet of
radiator and disconnect water inlet hose. To prevent flooding engine,
use a hose connected to radiator inlet. Use air in short bursts to
prevent damage to radiator. Continue flushing until water runs clear.
Engine
To flush engine, remove thermostat and replace housing.
Connect flushing gun to water outlet of engine. Flush using short air
bursts until water runs clean.
Heater Core
Flush heater core as described for radiator. Ensure heater
control valve is set to maximum heat position before flushing heater.

REFILLING
To prevent air from being trapped in engine block, engine
should be running when refilling cooling system. After system is full,
continue running engine until thermostat is open, then recheck fill
level. Do not overfill system.
TESTING
THERMOSTAT
1) Visually inspect thermostat for corrosion and proper
sealing of valve and seat. If okay, suspend thermostat and thermometer
in a 50/50 mixture of coolant and water. See Fig. 1. Do not allow
thermostat or thermometer to touch bottom of container. Heat water
until thermostat just begins to open.
2) Read temperature on thermometer. This is the initial
opening temperature and should be within specification. Continue
heating water until thermostat is fully open and note temperature.
This is the fully opened temperature. If either reading is not to
specification, replace thermostat.
Fig. 1: Testing Thermostat in Anti-Freeze/Water Solution
PRESSURE TESTING
A pressure tester is used to check both radiator cap and

complete cooling system. Test components as follows, following tool
manufacturer's instructions.
Radiator Cap
Visually inspect radiator cap, then dip cap into water and
connect to tester. Pump tester to bring pressure to upper limit of cap
specification. If cap fails to hold pressure, replace cap.
Fig. 2: Testing Radiator Pressure Cap
Cooling System
1) With engine off, wipe radiator filler neck seat clean.
Fill radiator to correct level. Attach tester to radiator and pump
until pressure is at upper level of radiator rating.
2) If pressure drops, inspect for external leaks. If no leaks
are apparent, detach tester and run engine until normal operating
temperature is reached. Reattach tester and observe. If pressure
builds up immediately, a possible leak exists from a faulty head
gasket or crack in head or block.
NOTE: Pressure may build up quickly. Release any excess pressure
or cooling system damage may result.
3) If there is no immediate pressure build up, pump tester to
within system pressure range (on radiator cap). Vibration of gauge
pointer indicates compression or combustion leak into cooling system.
Isolate leak by shorting each spark plug wire to cylinder block. Gauge
pointer should stop or decrease vibration when leaking cylinder is
shorted.

Removal
1) Disconnect the battery negative cable.
2) On vehicles equipped with A/C, remove the electrical
cooling fan and shroud assembly from the radiator to allow room to
rotate the engine with a socket and ratchet using the vibration damper
bolt.
3) Scribe a mark on the distributor housing below the left
side (past) the number one spark plug wire post of the distributor cap\
for reassembly reference for No 1 cylinder firing position.
4) Remove the distributor cap.
5) Turn the engine in a clockwise direction until the rotor
is approaching the scribed mark on the distributor housing. Then
slowly turn the engine until the timing mark on the crankshaft
vibration damper lines up with zero on the front cover timing scale.
See Fig. 24 .
NOTE: The timing mark is located on the edge of the vibration
damper closest to the front cover.
Fig. 24: View of Crankshaft Vibration Damper Timing Marks
Courtesy of Chrysler Motors.
6) Align the trailing edge of the rotor blade with the mark
previously scribed on the distributor housing. See Fig. 25.

ELECTROSTATIC DISCHARGE SENSITIVE (ESD) PARTS
WARNING: Many solid state electrical components can be damaged by
static electricity (ESD). Some will display a warning label,
but many will not. Discharge personal static electricity by
touching a metal ground point on the vehicle prior to
servicing any ESD sensitive component.
ENGINE OIL
CAUTION: Never use non-detergent or straight mineral oil.
CAUTION: Do not use reclaimed fluid, mineral oil, fluid that was
stored in old or open containers, or fluid inferior to AMC
Standard AM 4101. Be sure to handle the fluid in clean
containers that will not introduce even a slight amount of
foreign liquids or particles. Such contamination of fluid
could lead to hydraulic system failure.
ENGINE OIL FILTER (GASOLINE)
CAUTION: Verify that proper Oil Filter is being used. Filters with
metric threads (M20 x 1.5) must be used with some engines.
Other engines use SAE type (3/4" x 16) threads, and must
use an oil filter with these threads. Possible engine damage
can occur with improper oil filter.
ENGINE OIL FILTER (TURBO DIESEL ONLY)
CAUTION: The engine oil filter has METRIC threads. Use of a filter
with improper threads can result in oil leakage and
possible engine damage. Look for thread size symbol M20x1.5
on filter.
FUEL SYSTEM SERVICE
WARNING: DO NOT bleed fuel lines on hot engine, as high exhaust
temperatures could cause fire. Use care when bleeding fuel
lines, as fuel is under extreme pressure and could penetrate
skin, causing personal injury. Wear safety goggles and
protective clothing when bleeding fuel lines.
WARNING: Relieve fuel system pressure prior to servicing any fuel
system component.
HALOGEN BULBS
Halogen bulbs contain pressurized gas which may explode if
overheated. DO NOT touch glass portion of bulb with bare hands. Eye
protection should be worn when handling or working around halogen
bulbs.
RADIATOR CAP
CAUTION: Always disconnect the fan motor when working near the
radiator fan. The fan is temperature controlled and could
start at any time even when the ignition key is in the OFF
position. DO NOT loosen or remove radiator cap when cooling
system is hot.
STARTING FLUID USE (TURBO DIESEL)

HALOGEN BULBS
Halogen bulbs contain pressurized gas which may explode if
overheated. DO NOT touch glass portion of bulb with bare hands. Eye
protection should be worn when handling or working around halogen
bulbs.
OIL FILTER
CAUTION: The engine oil filter mount has metric threads. Use of a
filter with improper threads can result in oil leakage and
possible engine damage. Look for M20 x 1.5 symbol on the
filter.
RADIATOR CAP
CAUTION: Always disconnect the fan motor when working near the
radiator fan. The fan is temperature controlled and could
start at any time even when the ignition key is in the OFF
position. DO NOT loosen or remove radiator cap when cooling
system is hot.
RADIATOR FAN
Keep hands away from radiator fan. Fan is controlled by a
thermostatic switch which may come on or run for up to 15 minutes even
after engine is turned off.
WHEEL & TIRE WARNINGS
CAUTION: Replacing original tires with different size tires may
result in false speedometer and odometer indications. Check
with dealer before using different size tires on vehicle.
CAUTION: Ensure all 4 wheels on vehicle have same tire size, type
and circumference in order to provide proper vehicle
handling. DO NOT mix radial-ply with bias-ply or
bias-belted tires. On 4WD vehicles, if tire size, type and
circumference on all 4 wheels are not the same, gear
shifting will be adversely affected and can damage transfer
case.
CAUTION: Temporary-use spare tires are for emergency use only. DO
NOT drive vehicle faster than 50 MPH or more than 100 miles
when using spare tire. DO NOT operate vehicle in 4WD mode
when using spare tire, as damage to transfer case can
result. Temporary-use spare tires have a total tread life
of 3,000 miles.
SERVICE POINT LOCATIONS

Water Pump Malfunction Replace Water Pump
Fan Clutch Malfunction Replace Fan Clutch
Retarded Ignition Timing Reset Ignition Timing
Cooling Fan Malfunction Test Cooling Fan/
Circuit
Cooling Fan Motor
Malfunction Test Fan Motor
Cooling Fan Relay
Malfunction Test Fan Relay
Faulty Radiator Cap Replace Radiator Cap
Broken/Slipping Fan Belt Replace Fan Belt
Restricted Exhaust Repair Exhaust System









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Corrosion Impurities In Coolant Clean/Flush System








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Coolant Leakage Damaged hose Replace Hose
Leaky Water Pump Replace Water Pump
Damaged Radiator Seam Replace/Repair Radiator
Leaky Thermostat Cover Replace Thermostat
Cover
Cylinder Head Problem Check Head/Head Gasket
Leaky Freeze Plugs Replace Freeze Plugs









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Recovery System Inoperative
Loose and/or Defective
Radiator Cap Replace Radiator Cap
Overflow Tube Clogged
and/or Leaking Repair Tube
Recovery Bottle Vent
Restricted Clean Vent









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No Heater Core Flow
Collapsed Heater Hose Replace Heater Hose
Plugged Heater Core Clean/Replace Heater
Core
Faulty Heater Valve Replace Heater Valve









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GASOLINE ENGINE - MECHANICAL TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available