cooling DODGE TRUCK 1993 Service Owner's Guide

7 - 24
COOLING SYSTEM

• If the thermostat is being replaced, be sure that
the replacement is the specified thermostat for the vehicle model and engine type. Factory installed thermostat housings on 3.9L/5.2L/
5.9L engines are installed on a gasket with an anti-
stick coating. This will aid in gasket removal and
clean-up.
(1) Disconnect negative battery cable at battery.
(2) Drain cooling system until coolant level is be­
low thermostat. Refer to Draining Cooling System in
this group. If not equipped with air conditioning, pro­ ceed to step number 4.
(3) If equipped with air conditioning: (a) Remove the support bracket (rod) located
near the rear of generator (Fig. 28).
Fig.
28
Support
Bracket—Generator
Mounting

Bracket-to-intake
Manifold—
Typical
(b) The drive belt must be removed. Refer to Belt
Removal/Installation in the Engine Accessory
Drive Belt section of this group.
(c) The generator must be partially removed. Re­
move the two generator mounting bolts. Do not re­
move any wiring at generator. If equipped with

4WD,
unplug the 4WD indicator lamp wiring har­
ness (located near rear of generator).
(d) Remove generator. Position generator to gain
access for thermostat gasket removal.
(4) Remove upper radiator hose clamp. Special
Clamp Tool number 6094 (Fig. 29) may be used to re­
move the constant tension clamps. Remove upper ra­
diator hose at thermostat housing.
(5) Position the wiring harness (behind the ther­
mostat housing) to gain access to thermostat hous­ ing.
(6) Remove thermostat housing mounting bolts,
thermostat housing, gasket and thermostat (Fig. 30). Discard old gasket.
HOSE CLAMP HOSE

J9207-36

Fig.
29
Hose
Clamp
Tool
•THERMOSTAT
MACHINED GROOVE

J9207-14

Fig.
30 Thermostat—Gas
Engines

INSTALLATION-ALL GAS
POWERED
ENGINES
(1) Clean mating areas of intake manifold and
thermostat housing. (2) Install thermostat (spring side down) into re­
cessed machined groove on intake manifold (Fig. 30).
(3) Install gasket on intake manifold and over
thermostat (Fig. 30).
(4) Position the thermostat housing to the intake
manifold. Note the word FRONT stamped on the
housing (Fig. 31). For adequate clearance, this must
be placed towards the front of vehicle. The housing should be slightly angled forward after installation
to intake manifold.
(5) Install two housing-to-intake manifold bolts.
Tighten bolts to 23 N-m (200 in. lbs.) torque.

•

COOLING
SYSTEM
7 - 25

Fig.
31 Thermostat Position
CAUTION; Housing must
be
tightened
evenly and

thermostat must
be
centered into recessed groove in
intake manifold. If not, it may
result
in a
cracked
housing,
damaged intake manifold threads
or
cool­
ant
leak.
(6) Install upper radiator hose to thermostat hous­
ing. (7) Air conditioned vehicles: (a) Install generator. Tighten bolts to 41 N-m (30
ft. lbs.). (b) Install support bracket (generator mounting
bracket-to-intake manifold) (Fig. 28). Tighten bolts
to 54 N-m (40 ft. lbs.) torque.

CAUTION:
When installing
the
serpentine accessory
drive belt,
the
belt must
be
routed correctly.
If not,

the engine
may overheat due to the
water pump
ro­
tating in the
wrong direction. Refer
to
Belt Schemat­
ics
in the
Engine
Accessory
Drive Belt section
of

this group
for
correct engine belt routing.
The
cor­ rect belt with
the
correct length must
be
used.

(8) Fill cooling system. Refer to Refilling Cooling
System in this Group. (9) Connect negative battery cable to battery.
(10) Start and warm engine. Check for leaks.

THERMOSTAT OPERATIONr-5.9L DIESEL
ENGINE

The thermostat controls the operating temperature
of the engine by controlling the amount of coolant
flow to the radiator. When coolant temperature is be­ low 83°C (181°F), the thermostat is closed. Coolant is
routed back to the water pump inlet through the by­
pass (Fig. 32).

Fig.
32 Thermostat Operation—5.9L
Diesel
When coolant temperature reaches 83°C (181°F),
the thermostat begins to open allowing coolant flow
to the radiator. This provides quick engine warm-up and overall temperature control. The thermostat is
designed to provide a minimum engine operating
temperature of 83°C (181°F) and to be fully open for maximum coolant flow at approximately 95°C (203°F). Above 95°C (203°F), coolant temperature is
controlled by the radiator, fan and ambient tempera­

ture.

The thermostat is equipped with three air bleeds
on the flange. The air bleeds will vent air when the system is filled. It also acts as a check valve to block
the flow of coolant during engine operation.
REMOVAL-DIESEL

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 re­

use.
(1) Disconnect negative battery cable from battery.
(2) Remove accessory drive belt. Refer to Belt Re­
moval/Installation in the Engine Accessory Drive
Belt section in this group.
(3) Drain cooling system until coolant level is be­
low thermostat. Refer to Draining Cooling System in
this section.
(4) Remove radiator hose clamp and hose from
thermostat housing. Special Clamp Tool number 6094 (Fig. 29) may be used to remove the constant
tension clamps.
(5) Loosen generator pivot bolt.

7 - 26
COOLING
SYSTEM
————
Fig. 33 Generator
Mounting
Bolts—5.9L
Diesel (7) Remove thermostat housing mounting bolts.
(8) Remove thermostat housing, lifting bracket and
thermostat (Fig. 34).

Fig.
34 Thermostat Removal—5.9L
Diesel

(9) Clean the mating surfaces of the thermostat
housing and the cylinder head.
INSTALLA TION—DIESEL (1) Install the thermostat in the housing.
(2) Position the thermostat seal with the shoulder
towards the housing (Fig. 35).
(3) Install thermostat, lifting bracket, seal and
housing. Tighten the mounting bolts to 24 N°m (18 ft. lbs.) torque. (4) Position generator in place. Tighten mounting
bolt to 24 N*m torque. Tighten pivot bolt to 43 N*m (32 ft. lbs.) torque.
(5) Install accessory drive belt. Refer to Belt Re­
moval/Installation in the Engine Accessory Drive
Belt section of this group.
(6) Connect battery cable to battery. •

Fig.
35 Thermostat Seai—5.9L Diesel—Typical (7) Fill cooling system. Refer to Refilling Cooling
System in this group.

COOLANT
The cooling system is designed around the coolant.
Coolant flows through the engine water jacket ab­ sorbing heat produced during engine operation. The
coolant carries the heat to 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 transmis­sion 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%
Ethylene-Glycol-The corrosion inhibiting
additives in ethylene-glycol need the presence of wa­
ter to dissolve. Without water, additives form depos­ its in system. These act as insulation causing
temperature to rise to as high as 149°C (300°F). 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 -22°C (-8°F). 50/50 Ethylene-Glycol and Water-Is the recom­
mended mixture, it provides protection against freez­
ing to -37°C (-35°F). The antifreeze concentration
must always be 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 (6) Remove generator mounting bolt (Fig. 33).

•

COOLING
SYSTEM
7 - 27 down to -67.7°C (-90°F). 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 The presence of aluminum components in the cool­
ing system requires strict corrosion protection. Main­
tain coolant at specified level with a mixture of ethylene-glycol based antifreeze and water. Only use an antifreeze containing ALUGARD 340-2
™
such as
Mopar Antifreeze. If coolant becomes contaminated
or looses color, drain and flush cooling system and
fill with correctly mixed solution.
A 0.25 percent emulsifiable oil is added to the ra­
diator at the factory to prevent solder corrosion.

CAUTION:
Do not use
coolant
additives
that are

claimed
to
improve
engine
cooling.

COOLANT SERVICE-EXCEPT DIESEL 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), which­ ever occurs first.
COOLANT SERVICE-DIESEL ENGINE It is recommended that the cooling system be
drained and flushed every 24 months or 38,600 kilo­ meters (24,000 miles), whichever occurs first.
COOLANT LEVEL CHECK-ROUTINE Do not remove radiator cap for routine coolant
level inspections. The coolant level can be checked at the coolant reserve/overflow tank.
The coolant reserve/overflow system provides a
quick visual method for determining the coolant
level without removing the radiator pressure cap.
With engine idling and at normal operating temper­ ature, observe coolant level in coolant reserve/over­
flow tank. The coolant level should be between the MIN and MAX (diesel engine) or ADD and FULL (gas engines) marks.
ADDING ADDITIONAL COOLANT-ROUTINE Do not remove the radiator cap to add coolant
to the system. When adding coolant to maintain the correct level, do so at the coolant reserve/overflow
tank with a 50/50 mixture of ethylene-glycol anti­
freeze (containing Alugard 340-2 ™) and water. Re­ move the radiator cap only for testing or when
refilling the system after service. Removing cap un­ necessarily can cause loss of coolant and allow air to
enter system. This produces corrosion.
COOLANT LEVEL CHECK-SERVICE The cooling system is closed and designed to main­
tain coolant level to the top of the 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 the radiator, drain several ounces of coolant
from the radiator drain cock. Do this while observing
the coolant reserve/overflow system tank. The cool­ ant level in the reserve/overflow tank should drop
slightly. If not, inspect for a leak between radiator and coolant reserve/overflow system connection. Re­
move radiator cap. The coolant level should be to the
top of the radiator. If not and if coolant level in re­ serve/overflow tank is at the ADD (gas engines) or
MIN (5.9L diesel engine) mark, check for:
• An air leak in the coolant reserve/overflow tank
• An air leak in the radiator filler neck
• Leak in the pressure cap seal to the radiator filler
neck
LOW COOLANT LEVEL-AERATION If the coolant level in the radiator drops below the
top of the radiator core tubes, air will enter the sys­
tem. Low coolant level can cause the thermostat pellet
to be suspended in air instead of coolant. This will cause the thermostat to open later, which in turn causes higher coolant temperature. Air trapped in
cooling system also reduces the amount of coolant
circulating in the heater core. This may result in low
heat output.
DEAERATION As the engine operates, air trapped in the cooling
system gathers under the radiator cap. The next time
engine is operated, thermal expansion of coolant will
push trapped air past radiator cap into coolant re­ serve/overflow tank. Here it escapes to atmosphere in
the tank. When engine cools down the coolant, it will
be drawn from reserve/overflow tank into radiator to replace removed air.

DRAINING
COOLING
SYSTEM

WARNING:
DO NOT
REMOVE
THE
CYLINDER BLOCK DRAIN PLUGS
OR
LOOSEN THE RADIATOR
DRAIN PLUG
WITH
SYSTEM
HOT AND
UNDER

PRESSURE.
SERIOUS BURNS
FROM
COOLANT
CAN OCCUR.

7 - 28
COOLING SYSTEM

DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
(1) Start the engine and place the heater control
temperature selector in the Full On position. Engine vacuum is needed to actuate the heater controls.
(2) Turn the ignition off. (3) Do not remove radiator cap when draining cool­
ant from reserve/overflow tank. Open radiator drain
plug and when tank is empty, remove radiator cap. If
the coolant reserve/overflow tank does not drain, re­ fer to the Testing Cooling System for Leaks section
in this group. The coolant need not be removed from
tank unless the system is being refilled with fresh mixture.
(4) On vehicles equipped with gas powered en­

gines,
remove the cylinder block drain plugs. These are located on the sides of the block towards the
front of engine, just above the oil pan (Fig. 36).

Fig.
36 Drain Plugs—Gas Powered
Engines—Typical

(5) Remove radiator pressure cap.

REFILLING
THE
COOLING SYSTEM
Clean cooling system prior to refilling. Refer to
Cooling System Cleaning section of this group. (1) Install the cylinder block drain plugs (Fig. 36).
(2)
Close radiator drain plug.
(3) Fill the cooling system with a 50/50 mixture of
water and antifreeze. (4) Fill coolant reserve/overflow tank to the MAX
(5.9L diesel engine) or FULL (gas engines) mark. (5) Start and operate engine until thermostat
opens. Upper radiator hose should be warm to touch. (6) If necessary, add 50/50 water and antifreeze
mixture to the coolant reserve/overflow tank to main­
tain coolant level. This level should be between the MAX and MIN (5.9L diesel engine) or ADD and FULL (gas engines) marks. The level in the reserve/ overflow tank may drop below the MIN (or ADD)
mark after three or four warm-up and cool-down cy­

cles.

COOLING SYSTEM CLEANING/REVERSE FLUSHING
CLEMMING 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 cooling system is the forcing of
water through the cooling system. This is done using air pressure in the opposite direction of normal cool­
ant flow. It is usually only necessary with very dirty
systems with evidence of partial plugging.

REVERSE
FLUSHING
RADIATOR Disconnect radiator hoses from radiator inlet and
outlet. Attach a section of radiator hose to radiator
bottom outlet fitting and insert flushing gun. Con­
nect a water supply hose and air supply hose to flushing gun.

CAUTION:
Internal
radiator
pressure must
not'ex­

ceed 138 kPa (20 psi) as damage to
radiator
may re­
sult

Allow radiator to fill with water. When radiator is
filled, apply air in short blasts. Allow radiator to re­
fill between blasts. Continue this reverse flushing
until clean water flows out through rear of radiator cooling tube passages. Have radiator cleaned more extensively by a radiator repair shop.

REVERSE
FLUSHING
ENGINE-EXCEPT DIESEL Drain cooling system. Remove thermostat housing
and thermostat. Install thermostat housing. Discon­
nect radiator upper hose from radiator and attach
flushing gun to hose. Disconnect radiator lower hose
from water pump and attach a lead-away hose to wa­
ter pump inlet fitting.

CAUTION;
On vehicles equipped
with
a
heater
water

control
valve, be sure
heater
control
valve is closed

(heat
off). This
will
prevent
coolant
flow
with
scale

and
other
deposits
from
entering
heater
core.
Connect water supply hose and air supply hose to
flushing gun. Allow engine to fill with water. When engine is filled, apply air in short blasts, allowing system to fill between air blasts. Continue until
clean water flows through the lead away hose.

+
Fig.
37
Reverse-flushing—5.9L
Diesel

(5) Attach water supply hose to heater tube.
(6) Back-flush the engine until clean water exits
the water pump inlet.

CHEMICAL
CLEANING
In some instances, use a radiator cleaner (Mopar
Radiator Kleen or equivalent) before flushing. This
will soften scale and other deposits and aid flushing operation.

CAUTION;
Follow manufacturers instructions when

using
these
products.

TESTING
COOLING
SYSTEM
FOR
LEAKS
ULTRAVIOLET
LIGHT
METHOD
A leak detection additive is available through the
parts department that can be Sidfled to cooling sys­
tem. The additive is highly visible under ultraviolet
COOLING
SYSTEM
7 - 29

Fig.
38
Leak
Detection
Using
Black
Light—Typical

PRESSURE
TESTER
METHOD
The engine should be at normal operating temper­
ature. Recheck the system cold if cause of coolant
loss is not located during the warm engine examina­
tion.

WARNING:
HOT,
PRESSURIZED
COOLANT
CAN
CAUSE
INJURY
BY
SCALDING.

Carefully remove radiator pressure cap from filler
neck and check coolant level. Push down on cap to
disengage it from stop tabs. Wipe inside of filler neck and examine lower inside sealing seat for nicks,
cracks, paint, dirt and solder residue. Inspect radia­
tor-to-reserve/overflow tank hose for internal obstruc­
tions.
Insert a wire through the hose to be sure it is
not obstructed.
Inspect cams on outside of filler neck. If cams are
bent, seating of pressure cap valve and tester seal
will be affected. Bent cams can be reformed if done carefully. Attach pressure tester (7700 or an equiva­lent) to radiator filler neck (Fig. 39).
Operate tester pump to apply 103.4 kPa (15 psi)
pressure to system. If hoses enlarge excessively or
Remove lead away hose, flushing gun, water sup­
ply hose and air supply hose. Remove thermostat housing and install thermostat. Install thermostat
housing with a replacement gasket. Refer to Thermo­ stat Replacement. Connect radiator hoses. Refill cool­
ing system with correct antifreeze/water mixture.
Refer to Refilling the Cooling System.

REVERSE
FLUSHING
ENGINE-DIESEL
(1) Drain the cooling system. (2) Disconnect the upper hose from the radiator.
(3) Disconnect the radiator lower hose from the
water pump.

CAUTION;
Be
sure
the
heater
control valve is

closed
(heat
off).
This
will
prevent coolant flow
with

scale
and other
deposits
from entering the
heater
core.

(4) Remove the heater core inlet hose from tube
(Fig. 37). light (black light). Pour one ounce of additive into
cooling system. Place heater control unit in HEAT
position. Start and operate engine until radiator up­
per hose is warm to touch. Aim black light (tool C-4555 or an equivalent) at components to be
checked. If leaks are present, black light will cause additive to glow a bright green color.
The black light can be used in conjunction with a
pressure tester to determine if any external leaks ex­ ist (Fig. 38).

7 - 30
COOLING
SYSTEM

•

COOLING
SYSTEM

Fig.
39
Pressure
Testing
Cooling
System—Typical bulges while testing, replace as necessary. Observe
gauge pointer and determine condition of cooling sys­
tem according to following criteria:
Holds Steady: If pointer remains steady for two
minutes, serious coolant leaks are not present in sys­
tem. However, there could be an internal leak that does not appear with normal system test pressure. If
it is certain that coolant is being lost and leaks can­
not be detected, inspect for interior leakage or per­
form Internal Leakage Test.
Drops Slowly: Indicates a small leak or seepage is
occurring. Examine all connections for seepage or
slight leakage with a flashlight. Inspect radiator,

hoses,
gasket edges and heater. Seal small leak holes
with a Sealer Lubricant (or equivalent). Repair leak
holes and inspect system again with pressure ap­
plied.
Drops Quickly: Indicates that serious leakage is
occurring. Examine system for external leakage. If
leaks are not visible, inspect for internal leakage.
Large radiator leak holes should be repaired by a
reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION Remove engine oil pan drain plug and drain a
small amount of engine oil. If coolant is present in
the pan, it will drain first because it is heavier than
oil.
An alternative method is to operate engine for a
short period to churn the oil. After this is done, re­
move engine dipstick and inspect for water globules.
Also inspect transmission dipstick for water globules and transmission fluid cooler for leakage.

WARNING:
WITH
PRESSURE TESTER TOOL
7700
INSTALLED
ON
RADIATOR,
DO
NOT ALLOW
PRES­

SURE
TO
EXCEED
110 KPA (20
PSI). PRESSURE

WILL
BUILD
UP
QUICKLY
IF A
COMBUSTION LEAK

IS
PRESENT.
TO
RELEASE
PRESSURE,
ROCK

TESTER
FROM SIDE
TO
SIDE. WHEN REMOVING

TESTER,
DO NOT
TURN TESTER MORE THAN
1/2

TURN
IF
SYSTEM
IS
UNDER
PRESSURE.
Operate engine without pressure cap on radiator
until thermostat opens. Attach a Pressure Tester to
filler neck. If pressure builds up quickly it indicates a combustion leak exists. This is usually the result of
a cylinder head gasket leak or crack in engine. Re­
pair as necessary.
If there is not an immediate pressure increase,
pump the Pressure Tester. Do this until indicated
pressure is within system range of 110 kPa (16 psi). Fluctuation of gauge pointer indicates compression or
combustion leakage into cooling system.
Because the vehicle is equipped with a catalytic
converter, do not remove spark plug cables or short
out cylinders (non-diesel engines) to isolate compres­
sion leak.
If the needle on dial of pressure tester does not
fluctuate, race engine a few times to check for an ab­ normal amount of coolant or steam. This would be
emitting from exhaust pipe. Coolant or steam from
exhaust pipe may indicate a faulty cylinder head
gasket, cracked engine cylinder block or cylinder
head. A convenient check for exhaust gas leakage into
cooling system is provided by a commercially avail­ able Block Leak Check tool. Follow manufacturers
instructions when using this product.
COMBUSTION LEAKAGE TEST-WITHOUT
PRESSURE TESTER DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.

WARNING:
DO NOT
REMOVE CYLINDER BLOCK DRAIN PLUGS
OR
LOOSEN RADIATOR DRAIN-

COCK
WITH
SYSTEM
HOT AND
UNDER PRES­

SURE.
SERIOUS BURNS FROM COOLANT
CAN

OCCUR.

Drain sufficient coolant to allow thermostat re­
moval. Refer to Thermostat Replacement. Disconnect
water pump drive belt. Add coolant to radiator to bring level to within 6.3
mm (1/4 in) of top of thermostat housing.

CAUTION:
Avoid
overheating.
Do not
operate
en­

gine
for an
excessive
period
of
time.
Open
drain-

cock
immediately
after
test
to
eliminate
boil
over.

Start engine and accelerate rapidly three times, to
approximately 3000 rpm while observing coolant. If
internal engine combustion gases% are leaking into
cooling system, bubbles will appear in coolant. If
bubbles do not appear, internal combustion gas leak­ age is not present.

COOLANT
RESERVE/0WERFL0W
SYSTEM
The coolant reserve/overflow system (Fig. 40 or 41)
works in conjunction with the radiator pressure cap.

•

COOLING
SYSTEM
7 - 31 It utilizes thermal expansion and contraction of cool­
ant to keep coolant free of trapped air. It provides a
volume for expansion and contraction of coolant. It
also provides a convenient and safe method for
checking coolant level and adjusting level at atmo­
spheric pressure. This is done without removing ra­
diator pressure cap. It also provides some reserve
coolant to cover minor leaks and evaporation or boil­
ing losses.
FAN

SHROUD
J9107-67

Fig.
40 Coolant Reserve/Overflow Tank—Gas
Engines
Fig.
41 Coolant Reserve/Overflow Tank—Diesel
Engines

Refer to Coolant Level Check—Service, Deaeration
and Radiator Pressure Cap sections in this group for
coolant reserve/overflow system operation and ser­

vice.
Should the reserve/overflow tank become coated
with corrosion or emulsifiable oil, it can be cleaned
with detergent and water. Rinse tank thoroughly be­
fore refilling cooling system as described in the Cool­ ant section of this group.

TANK REMOVAL
(1) Remove overflow hose at reserve/overflow tank.
(2) Unsnap the coolant reserve/overflow tank from
fan shroud. Lift straight up. The fan shroud is
equipped with T-shaped slots to attach the tank.

TANK INSTALLATION
(1) Snap tank into fan shroud.
(2) Install overflow hose to tank.

RADIATOR
PRESSURE
CAP
Radiators are equipped with a pressure cap, which
releases pressure at some point within a range of 97- 124 kPa (14-18 psi). The pressure relief point (in
pounds) is engraved on top of cap. 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. 42) contains a
spring-loaded pressure relief valve that opens when
system pressure reaches release range of 97-124 kPa (14-18 psi).

Fig.
42 Radiator
Pressure
Cap and
Filler
Neck—Typical
A vent valve in the center of cap allows a small
coolant flow through cap when coolant is below boil­
ing temperature. The valve is completely closed
when boiling point is reached. As the coolant cools, it contracts and creates a vacuum in the cooling sys­
tem. This causes the vacuum valve to open and cool­ ant in the reserve/overflow tank to be drawn through
its connecting hose into radiator. If the vacuum valve
is stuck shut, the radiator hoses will collapse on cool-
down. Clean the vent valve (Fig. 42).
A rubber gasket seals radiator filler neck to pre­
vent leakage. This is done to keep system under

7 - 32
COOLING
SYSTEM

• pressure. It also maintains vacuum during coolant
cool-down allowing coolant to return from reserve/
overflow tank.

RADIATOR
CAP-TO-FILLER
NECK

SEAL-PRESSURE RELIEF CHECK The pressure cap upper gasket (seal) pressure relief
can be tested by removing overflow hose from radia­
tor filler neck nipple. Attach hose of pressure tester
tool 7700 or equivalent to nipple. It will be necessary
to disconnect hose from its adapter for filler neck.
Pump air into radiator. The pressure cap upper gas­
ket should relieve at 69-124 kPa (10-18 psi) and hold
pressure at a minimum of 55 kPa (8 psi).

WARNING;
THE
WARNING WORDS
-DO NOT
OPEN HOT—
ON
RADIATOR PRESSURE CAP, ARE
A SAFETY PRECAUTION. WHEN
HOT,
PRESSURE BUILDS
UP IN
COOLING SYSTEM.
TO
PREVENT
SCALDING
OR
INJURY, RADIATOR
CAP
SHOULD NOT
BE
REMOVED WHILE SYSTEM
IS HOT

AND/OR UNDER
PRESSURE.

Do not remove radiator cap at any time except for
the following purposes: • Check and adjust antifreeze freeze point
• Refill system with new antifreeze
• Conducting service procedures
• Checking for vacuum leaks

WARNING;
IF
VEHICLE HAS BEEN RUN RECENTLY,

WAIT
AT
LEAST
15
MINUTES BEFORE REMOVING
RADIATOR CAP.
WITH
A
RAG, SQUEEZE RADIA­
TOR UPPER HOSE
TO
CHECK
IF
SYSTEM
IS UN­
DER
PRESSURE.
PLACE
A RAG
OVER
CAP AND

WITHOUT
PUSHING
CAP
DOWN, ROTATE
IT

COUNTER-CLOCKWISE
TO
FIRST STOP. ALLOW FLUID
TO
ESCAPE THROUGH
THE
COOLANT RE­
SERVE/OVERFLOW HOSE
INTO
RESERVE/OVER­ FLOW TANK. SQUEEZE RADIATOR UPPER HOSE
TO DETERMINE WHEN PRESSURE HAS BEEN RE­
LEASED.
WHEN COOLANT AND STEAM STOP BE­
ING PUSHED
INTO
TANK AND SYSTEM PRESSURE
DROPS,
REMOVE RADIATOR CAP COMPLETELY.
PRESSURE
TESTING
RADIATOR
CAPS
Remove cap from radiator. Be sure that sealing
surfaces are clean. Moisten rubber gasket with water
and install cap on pressure tester 7700 or an equiv­
alent (Fig. 43). Operate tester pump to bring pressure to 104 kPa
(15 psi) on gauge. If pressure cap fails to hold pres­
sure of at least 97 kPa (14 psi) replace cap. Refer to
CAUTION below. The pressure cap may test properly while posi­
tioned on tool 7700 (or equivalent). It may not hold
pressure or vacuum when installed on radiator. If so,
Fig.
43
Pressure
Testing Radiator Cap
inspect radiator filler neck and cap's top gasket for
damage. Also inspect for dirt or distortion that may
prevent cap from sealing properly.

CAUTION:
Tool
7700
is
very
sensitive
to
small
air
leaks,
which
will
not
cause
cooling
system
prob­

lems.
A
pressure
cap
that
does
not
have
a
history

of
coolant
loss
should
not be
replaced
just
because
it
leaks
slowly
when
tested
with
this
tool.
Add
water

to
tool.
Turn
tool
upside
down
and
recheck
pres­
sure
cap to
confirm
that
cap
needs
replacement.

INSPECTION
Hold cap at eye level, right side up. The vent valve
(Fig. 42) at bottom of cap should open. If rubber gas­
ket has swollen and prevents vent valve from open­ ing, replace cap.
Hold cap at eye level, upside down. If any light can
be seen between vent valve and rubber gasket, re­ place cap. Do not use a replacement cap that has a spring to hold vent shut. A replacement cap
must be the type designed for a coolant reserve/over­
flow system with a completely sealed diaphragm spring and a rubber gasket. This gasket is used to
seal to radiator filler neck top surface. Use of proper
cap will allow coolant return to radiator.

RADIATORS
3.9L, 5.2L and 5.9L Gas Engines: The radiator is a
down-flow type (vertical tubes). 5.9L Diesel Engines: The radiator is a cross-flow
type (horizontal tubes).

•

COOLING
SYSTEM
7 - 33 The radiator supplies sufficient heat transfer to
cool the engine and automatic transmission (if equipped).

RADIATOR COOLANT FLOW CHECK
Use the following procedure to determine if coolant
is flowing through the cooling system.
(1) Idle engine until operating temperature is
reached. If the upper radiator hose is warm to the
touch, the thermostat is opening and coolant is flow­ ing to the radiator.

WARNING:
HOT,
PRESSURIZED COOLANT
CAN
CAUSE
INJURY
BY
SCALDING. USING
A
RAG
TO

COVER
THE
RADIATOR
PRESSURE
CAP,
OPEN RADIATOR
CAP
SLOWLY
TO THE
FIRST STOP.
THIS
WILL
ALLOW
ANY
BUILT-UP
PRESSURE
TO
VENT
TO
THE
RESERVE/OVERFLOW TANK. AFTER
PRESSURE
BUILD-UP
HAS
BEEN RELEASED,
RE­

MOVE
CAP
FROM FILLER NECK.

(2) Drain a small amount of coolant from the radi­
ator until the ends of the radiator tubes are visible
through the filler neck. Idle the engine at normal op­
erating temperature. If coolant is flowing past the
exposed tubes, the coolant is circulating.

RADIATOR REMOVAL-EXCEPT DIESEL
(1) Disconnect negative battery cable from battery.

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.

(2) Drain the cooling system. Refer to Draining
Cooling System.
(3) Disconnect throttle cable from clip at radiator
fan shroud. (4) Remove hose clamps and hoses from radiator.
Special Clamp Tool number 6094 (Fig. 44) may be
used to remove the constant tension clamps.
(5) Remove coolant reserve/overflow tank hose
from radiator filler neck nipple.
(6) If equipped with an automatic transmission
(except diesel), disconnect oil cooler hoses at radiator
lower tank.
(7) Remove fan shroud mounting bolts/clips and
position shroud rearward on engine (Fig. 45). (8) Loosen radiator lower mounting bolts. Remove
the upper mounting bolts. Lift radiator straight up and out of engine compartment. Take care not to
damage radiator cooling fins or tubes.

INSTALLATION
(1) Position shroud rearward on engine.
(2) Slide radiator into position. Place behind radi­
ator support with lower mounting holes (slots) rest-
HOSE
CLAMP
TOOL
6094
HOSE

CLAMP

J9207-36

Fig.
44
Hose
Clamp
Tool
RADIATOR SHROUD
MOUNTING MOUNTING
BOLTS
CUPS
RADIATOR
V1

FAN SHROUD^
J9207-44
Fig.
45 Radiator and Fan
Shroud—Gas Engines

ing on loosened bottom mounting bolts. Install upper
mounting bolts. Tighten all mounting bolts to 11
N*m (95 in. lbs.) torque.
(3) Connect radiator hoses.
(4) Connect transmission oil cooler lines to bottom
tank. Tighten hose clamps to 4 N#m (35 in. lbs.)
torque.
(5) Position fan shroud on radiator flange. Install
mounting clips (Fig. 45).
(6) Connect throttle cable to fan shroud.
(7) Position heater controls to full heat position.
(8) Fill cooling system with coolant. Refer to Refill­
ing Cooling System in this group.
(9) Operate engine until it reaches normal temper­
ature. Check cooling system and automatic transmis­
sion (if equipped) fluid levels.

RADIATOR REMOVAL-DIESEL
(1) Disconnect negative battery cable from battery.