1994 JEEP CHEROKEE coolant temperature

REMOVAL
(1) Disconnect the electrical connector from the
sensor.
(2) Remove the sensor from the intake manifold.
INSTALLATION
(1) Install the sensor into the intake manifold.
Tighten the sensor to 28 Nzm (20 ft. lbs.) torque.
(2) Connect the electrical connector to the sensor.
CRANKSHAFT POSITION SENSOR
For description, operation and removal/installation
procedures, refer to Group 8D, Ignition Systems in
this manual.
ENGINE COOLANT TEMPERATURE SENSOR
The coolant temperature sensor is installed in the
thermostat housing (Fig. 5).
REMOVAL
(1) Drain cooling system until the coolant level is
below the cylinder head. Observe theWARNINGSin
Group 7, Cooling.(2) Disconnect the coolant temperature sensor wire
connector.
(3) Remove the sensor from the thermostat hous-
ing (Fig. 5).
INSTALLATION
(1) Install coolant temperature sensor into the cyl-
inder block. Tighten to 28 Nzm (21 ft. lbs.) torque.
(2) Connect the wire connector.
(3) Fill the cooling system. Refer to Group 7, Cool-
ing System.
FUEL FILTER
Refer to the Fuel Delivery System section of this
group for removal/installation procedures.
FUEL INJECTOR
REMOVAL
(1) Remove the fuel rail. Refer to Fuel Rail Re-
moval in this section.
(2) Remove the clip(s) that retain the fuel injec-
tor(s) to the fuel rail (Fig. 6).
Fig. 3 Sensor LocationÐ2.5L Engine
Fig. 4 Sensor LocationÐ4.0L Engine
Fig. 5 Engine Coolant Temperature SensorÐTypical
Fig. 6 Injector Retaining Clips
JFUEL SYSTEM 14 - 55

COOLING SYSTEM
CONTENTS
page page
DIAGNOSIS............................. 4
ENGINE ACCESSORY DRIVE BELTS........ 31
ENGINE BLOCK HEATER................. 37GENERAL INFORMATION.................. 1
SERVICE PROCEDURES................... 9
SPECIFICATIONS....................... 38
GENERAL INFORMATION
Throughout this group, references are made to par-
ticular vehicle models by alphabetical designation
(XJ or YJ) or by the particular vehicle nameplate. A
chart showing a breakdown of alphabetical designa-
tions is included in the Introduction section at the
beginning of this manual.
COOLING SYSTEM
The cooling system regulates engine operating tem-
perature. It allows the engine to reach normal oper-
ating temperature as quickly as possible, maintains
normal operating temperature and prevents over-
heating.
The cooling system also provides a means of heat-
ing the passenger compartment and cooling the auto-
matic transmission fluid (if equipped). The cooling
system is pressurized and uses a centrifugal water
pump to circulate coolant throughout the system.
An optional factory installed heavy duty cooling
package is available on most models. The package
consists of a radiator that has an increased numberof cooling fins. XJ models equipped with a 4.0L 6 cyl-
inder engine and heavy duty cooling and/or air con-
ditioning also have an auxiliary electric cooling fan.
COOLING SYSTEM COMPONENTS
The cooling system consists of:
²A radiator
²Cooling fan (mechanical and/or electrical)
²Thermal viscous fan drive
²Fan shroud
²Radiator pressure cap
²Thermostat
²Coolant reserve/overflow system
²Transmission oil cooler (if equipped with an auto-
matic transmission)
²Coolant
²Water pump
²Hoses and hose clamps
SYSTEM COOLANT ROUTING
For cooling system flow routings, refer to Figs. 1, 2,
3or4.
JCOOLING SYSTEM 7 - 1

(14) Tighten pivot bolt B (Fig. 6) to 27 Nzm (20 ft.
lbs.) torque.
(15) Tighten locknut C (Fig. 6) to 27 Nzm (20 ft.
lbs.) torque.
(16) After the power steering pump has been tight-
ened, recheck belt tension.
(17) Fill cooling system with coolant and check for
leaks. Refer to Refilling Cooling System in this
group.
(18) Connect battery cable to battery.
(19) Start and warm the engine. Check for leaks.
THERMOSTAT
DESCRIPTION AND OPERATION
A pellet-type thermostat controls the operating
temperature of the engine by controlling the amount
of coolant flow to the radiator. On all engines the
thermostat is closed below 195ÉF (90ÉC). Above this
temperature, coolant is allowed to flow to the radia-
tor. This provides quick engine warmup and overall
temperature control.
An arrow plus the wordUPis stamped on the
front flange next to the air bleed. The wordsTO
RADare stamped on one arm of the thermostat.
They indicate the proper installed position.
The same thermostat is used for winter and sum-
mer seasons. An engine should not be operated with-
out a thermostat, except for servicing or testing.
Operating without a thermostat causes other prob-
lems. These are: longer engine warmup time, unreli-
able warmup performance, increased exhaust
emissions and crankcase condensation. This conden-
sation can result in sludge formation.
Fig. 10 YJ Models with 4.0L Engine and XJ Models
with 2.5L EngineÐWith A/C
Fig. 11 YJ Models With 2.5L or 4.0L Engine and XJ
Models with 2.5L EngineÐWithout A/C
Fig. 12 XJ Models with 4.0L EngineÐWithout A/C
Fig. 13 XJ Models With 4.0L EngineÐWith A/C
JCOOLING SYSTEM 7 - 13

CAUTION: Do not operate an engine without a ther-
mostat, except for servicing or testing.
ON-BOARD DIAGNOSTICS
XJ and YJ models are equipped with On-Board Di-
agnostics for certain cooling system components. Re-
fer to On-Board Diagnostics (OBD) in the Diagnosis
section of this group for additional information. If the
powertrain control module (PCM) detects low engine
coolant temperature, it will record a Diagnostic Trou-
ble Code (DTC) in the PCM memory. The DTC num-
ber for low coolant temperature is 17. Do not change
a thermostat for lack of heat as indicated by the in-
strument panel gauge or heater performance unless a
DTC number 17 is present. Refer to the Diagnosis
section of this group for other probable causes. For
other DTC numbers, refer to On-Board Diagnostics
in the General Diagnosis section of group 14, Fuel
Systems.
The DTC can also be accessed through the DRB
scan tool. Refer to the appropriate Powertrain Diag-
nostic Procedures manual for diagnostic information
and operation of the DRB scan tool.
REMOVAL
WARNING: DO NOT LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND PRES-
SURIZED. SERIOUS BURNS FROM THE COOLANT
CAN OCCUR.
DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
(1) Drain the coolant from the radiator until the
level is below the thermostat housing.
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 (NUM-
BER 6094) (FIG. 14). SNAP-ON CLAMP TOOL (NUM-
BER HPC-20) MAY BE USED FOR LARGER
CLAMPS. ALWAYS WEAR SAFETY GLASSES
WHEN SERVICING CONSTANT TENSION CLAMPS.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only an original equipment clamp
with matching number or letter.
(2) Remove radiator upper hose and heater hose at
thermostat housing.
(3) Disconnect wiring connector at engine coolant
temperature sensor.(4) Remove thermostat housing mounting bolts,
thermostat housing, gasket and thermostat (Fig. 15).
Discard old gasket.
(5) Clean the gasket mating surfaces.
INSTALLATION
(1) Install the replacement thermostat so that the
pellet, which is encircled by a coil spring, faces the
engine. All thermostats are marked on the outer
flange to indicate the proper installed position.
(a) Observe the recess groove in the engine cyl-
inder head (Fig. 16).
(b) Position thermostat in groove with arrow and
air bleed hole on outer flange pointing up.
(2) Install replacement gasket and thermostat
housing.
Fig. 14 Hose Clamp ToolÐTypical
Fig. 15 Thermostat Removal/Installation
7 - 14 COOLING SYSTEMJ

CAUTION: Tightening the thermostat housing un-
evenly or with the thermostat out of its recess, may
result in a cracked housing.
(3) Tighten the housing bolts to 20 Nzm (15 ft. lbs.)
torque.
(4) Install hoses to thermostat housing.
(5) Install electrical connector to coolant tempera-
ture sensor.
(6) Be sure that the radiator draincock is tightly
closed. Fill the cooling system to the correct level
with the required coolant mixture. Refer to Refilling
Cooling System in this group.
(7) Start and warm the engine. Check for leaks.
COOLANT
GENERAL INFORMATION
The cooling system is designed around the coolant.
Coolant flows through the engine water jackets ab-
sorbing heat produced during engine operation. The
coolant carries heat to the radiator and heater core.
Here it is transferred to the ambient air passing
through the radiator and heater core fins. The cool-
ant also removes heat from the automatic transmis-
sion fluid in vehicles equipped with an automatic
transmission.
COOLANT PERFORMANCE
The required ethylene-glycol (antifreeze) and water
mixture depends upon climate and vehicle operating
conditions. The coolant performance of various mix-
tures follows:
Pure Water-Water can absorb more heat than a
mixture of water and ethylene-glycol. This is for pur-pose of heat transfer only. Water also freezes at a
higher temperature and allows corrosion.
100 percent Ethylene-Glycol-The corrosion inhib-
iting additives in ethylene-glycol need the presence
of water to dissolve. Without water, additives form
deposits in system. These act as insulation causing
temperature to rise to as high as 149ÉC (300ÉF). This
temperature is hot enough to melt plastic and soften
solder. The increased temperature can result in en-
gine detonation. In addition, 100 percent ethylene-
glycol freezes at -22ÉC (-8ÉF).
50/50 Ethylene-Glycol and Water-Is the recom-
mended mixture, it provides protection against freez-
ing to -37ÉC (-35ÉF). The antifreeze concentration
must alwaysbe a minimum of 44 percent, year-
round in all climates. If percentage is lower, engine
parts may be eroded by cavitation. Maximum protec-
tion against freezing is provided with a 68 percent
antifreeze concentration, which prevents freezing
down to -67.7ÉC (-90ÉF). A higher percentage will
freeze at a warmer temperature. Also, a higher per-
centage of antifreeze can cause the engine to over-
heat because specific heat of antifreeze is lower than
that of water.
CAUTION: Richer antifreeze mixtures cannot be
measured with normal field equipment and can
cause problems associated with 100 percent ethyl-
ene-glycol.
COOLANT SELECTION-ADDITIVES
Coolant should be maintained at the specified level
with a mixture of ethylene glycol-based antifreeze
and low mineral content water. Only use an anti-
freeze containing ALUGARD 340-2 Ÿ.
CAUTION: Do not use coolant additives that are
claimed to improve engine cooling.
COOLANT SERVICE
It is recommended that the cooling system be
drained and flushed at 84,000 kilometers (52,500
miles), or 3 years, whichever occurs first. Then every
two years, or 48,000 kilometers (30,000 miles),
whichever occurs first.
COOLANT LEVEL CHECKÐROUTINE
Do not remove radiator cap for routine coolant
level inspections. The coolant level can be
checked at coolant reserve/overflow tank.
The coolant reserve/overflow system provides a
quick visual method for determining coolant level
without removing radiator pressure cap. With engine
idling and at normal operating temperature, observe
coolant level in reserve/overflow tank. The coolant
level should be between ADD and FULL marks.
Fig. 16 Thermostat Recess
JCOOLING SYSTEM 7 - 15

ADDING ADDITIONAL COOLANTÐROUTINE
Do not remove radiator cap to add coolant to
system.When adding coolant to maintain correct
level, do so at coolant reserve/overflow tank. Use a
50/50 mixture of ethylene-glycol antifreeze contain-
ing Alugard 340-2 Ÿ and low mineral content water.
Remove radiator cap only for testing or when refill-
ing system after service. Removing cap unnecessarily
can cause loss of coolant and allow air to enter sys-
tem, which produces corrosion.
COOLANT LEVEL CHECK-SERVICE
The cooling system is closed and designed to main-
tain coolant level to top of radiator.
WARNING: DO NOT OPEN RADIATOR DRAINCOCK
WITH ENGINE RUNNING OR WHILE ENGINE IS HOT
AND COOLING SYSTEM IS UNDER PRESSURE.
When vehicle servicing requires a coolant level
check in radiator, drain several ounces of coolant
from radiator drain cock. Do this while observing
coolant reserve/overflow system tank. The coolant
level in reserve/overflow tank should drop slightly. If
not, inspect for a leak between radiator and coolant
reserve/overflow system connection. Remove radiator
cap. The coolant level should be to top of radiator. If
not and if coolant level in reserve/overflow tank is at
ADD mark, check for:
²An air leak in coolant reserve/overflow tank or its
hose
²An air leak in radiator filler neck
²Leak in pressure cap seal to radiator filler neck
LOW COOLANT LEVEL-AERATION
If the coolant level in radiator drops below top of
radiator core tubes, air will enter cooling system.
Low coolant level can cause thermostat pellet to be
suspended in air instead of coolant. This will cause
thermostat to open later, which in turn causes higher
coolant temperature. Air trapped in cooling system
also reduces amount of coolant circulating in heater
core resulting in low heat output.
DEAERATION
As the engine operates, any air trapped in cooling
system gathers under the radiator cap. The next time
the engine is operated, thermal expansion of coolant
will push any trapped air past radiator cap into the
coolant reserve/overflow tank. Here it escapes to the
atmosphere into the tank. When the engine cools
down the coolant, it will be drawn from the reserve/
overflow tank into the radiator to replace any re-
moved air.
DRAINING COOLING SYSTEM
ALL MODELSÐEXCEPT XJ WITH 4.0L ENGINE
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM COOLANT
CAN OCCUR.
DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
DO NOT remove the radiator cap when draining
the coolant from the reserve/overflow tank. Open the
radiator draincock and when the tank is empty, re-
move the radiator cap. The coolant does not have to
be removed from the tank unless the system is being
refilled with a fresh mixture.
(1) Drain the coolant from the radiator by loosen-
ing the draincock.
(2) Drain coolant from engine as follows:
(a) On 2.5L engines (all models) by removing
drain plug at left rear side of block.
(b) On 4.0L engines by removing the drain plug
or coolant temperature sensor on the left side of
the block (Fig. 17).
XJ MODELS WITH 4.0L ENGINE
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM COOLANT
CAN OCCUR.
Fig. 17 Draining CoolantÐ4.0L Engine
7 - 16 COOLING SYSTEMJ

DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
(1) Remove radiator pressure cap.
(2) For access to radiator draincock, remove radia-
tor grille (Fig. 18).
(3) Attach one end of a 24 inch long X 1/4 inch ID
hose to the radiator draincock. Put the other end into
a clean container. Open draincock and drain coolant
from radiator.
(4) Drain coolant from engine by removing the
drain plug and coolant temperature sensor on left
side of block (Fig. 17).
REFILLING COOLING SYSTEM
YJ MODELS
(1) Remove draining hose. Tighten the radiator
draincock and the cylinder block drain plug(s).
(2) Fill system using a 50/50 mixture of water and
antifreeze. This is described in the Coolant section of
this group. Fill the radiator to the top and install the
radiator cap. Add sufficient coolant to the reserve/
overflow tank to raise the level to the FULL mark.
(3) Operate the engine with the radiator cap and
reserve/overflow tank cap in place. After the engine
has reached the normal operating temperature, shut
the engine off and allow it to cool.
(4) Add coolant to the reserve/overflow tank as
necessary.Only add coolant when the engine is
cold. Coolant level in a warm engine will be
higher due to thermal expansion.
XJ MODELS
(1) Tighten the radiator draincock and the cylinder
block drain plug(s). If removed, install coolant tem-
perature sensor (4.0L engine).
(2) Fill system using a 50/50 mixture of water and
antifreeze as described in the Coolant section of this
group. Fill radiator to top and install radiator cap.
Add sufficient coolant to reserve/overflow tank to
raise level to FULL mark.
(3) With heater control unit in the HEAT position,
operate engine with radiator cap in place.
(4) After engine has reached normal operating
temperature, shut engine off and allow it to cool.
(5) Add coolant to reserve/overflow tank as neces-
sary.Only add coolant when the engine is cold.
Coolant level in a warm engine will be higher
due to thermal expansion.
COOLING SYSTEM CLEANING/REVERSE FLUSHING
CAUTION: The cooling system normally operates at
97-to-124 kPa (14-to-18 psi) pressure. Exceeding
this pressure may damage the radiator or hoses.
CLEANING
Drain cooling system and refill with water. Run
engine with radiator cap installed until upper radia-
tor hose is hot. Stop engine and drain water from
system. If water is dirty, fill system with water, run
engine and drain system. Repeat until water drains
clean.
REVERSE FLUSHING
Reverse flushing of the cooling system is the forc-
ing of water through the cooling system. This is done
using air pressure in the opposite direction of normal
coolant flow. It is usually only necessary with very
dirty systems with evidence of partial plugging.
REVERSE FLUSHING RADIATOR
Disconnect the radiator hoses from the radiator fit-
tings. Attach a section of radiator hose to the radia-
tor bottom outlet fitting and insert the flushing gun.
Connect a water supply hose and air supply hose to
the flushing gun.
CAUTION: The cooling system normally operates at
97-to-124 kPa (14-to-18 psi) pressure. Exceeding
this pressure may damage the radiator or hoses.
Allow the radiator to fill with water. When radia-
tor is filled, apply air in short blasts allowing radia-
tor to refill between blasts. Continue this reverse
flushing until clean water flows out through rear of
radiator cooling tube passages. For more information,
refer to operating instructions supplied with flushing
equipment. Have radiator cleaned more extensively
by a radiator repair shop.
Fig. 18 Draincock AccessÐXJ Models with 4.0L
Engine
JCOOLING SYSTEM 7 - 17

The coolant reserve/overflow system consists of a
radiator mounted pressurized cap, a plastic reserve/
overflow tank (Figs. 21, 22 or 23), a tube connecting
the radiator and tank, and an overflow tube on the
side of the tank.
TANK REMOVAL/INSTALLATION
(1) Remove the tube clamp at the tank and remove
tube.(2) On YJ models, remove the windshield washer
reservoir and its mounting bracket.
(3) Remove the tank mounting bolts and remove
tank.
(4) Reverse the preceding steps for installation.
RADIATOR PRESSURE CAP
All radiators are equipped with a pressure cap.
This cap releases pressure at some point within a
range of 83-110 kPa (12-16 psi). The pressure relief
point (in pounds) is engraved on top of the cap (Fig.
24).
The cooling system will operate at pressures
slightly above atmospheric pressure. This results in a
higher coolant boiling point allowing increased radi-
ator cooling capacity. The cap (Fig. 24) contains a
spring-loaded pressure relief valve. This valve opens
when system pressure reaches the release range of
83-110 kPa (12-16 psi).
A vent valve in the center of the cap allows a small
coolant flow through the cap when coolant is below
boiling temperature. The valve is completely closed
when boiling point is reached. As coolant cools, it
contracts and creates a vacuum in the cooling sys-
tem. This causes the vacuum valve to open and cool-
ant in reserve/overflow tank to be drawn through
connecting hose into radiator. If the vacuum valve is
stuck shut, radiator hoses will collapse on cool-down.
A rubber gasket seals the radiator filler neck. This
is done to maintain vacuum during coolant cool-down
and to prevent leakage when system is under pres-
sure.
Fig. 21 Reserve/Overflow TankÐYJ Models
Fig. 22 Reserve/Overflow TankÐXJ ModelsÐExcept
Right Hand Drive
Fig. 23 Reserve/Overflow TankÐXJ ModelsÐWith
Right Hand Drive
7 - 20 COOLING SYSTEMJ