1993 DODGE TRUCK Service Repair Manual

7-10 COOLING SYSTEM
•
DIESEL
COOLING SYSTEM
DIAGNOSIS

CONDITION AND CHECKS
DIAGNOSIS

OPTIONAL
60»F
GAUGE
READS
LOW 30° TO 40°
GAUGE
TRAVEL
IS
NORMAL
(1)
Verify
gauge reading. Is a low
temperature
indicated?
(2) Thermostat stuck in open position?
(3) Is the gauge reading in the cold range?
(4) Low coolant
level
during cold ambient temperatures (accom­ panied
with
poor
heater
performance).
(5) Coolant
level
is correct.
MID

Normal
Gauge
Travel

(1) Inspect
temperature
gauge sending unit. Refer to Group 8,
Electrical. Repair or replace sending
unit
as necessary.
(2) If
Yes,
replace the thermostat. If not, the thermostat is not the
cause
of the low gauge
reading.

(3) Inspect for disconnected sending
unit
electrical
connector or
incorrect
sending unit. Ensure
that
gauge sending
unit
is in­
stalled and not an indicator light switch.
(4) WARNING: DO NOT REMOVE THE RADIATOR CAP
OF
A HOT, PRESSURIZED ENGINE. SERIOUS IN­
JURY CAN RESULT FROM SCALDING COOLANT. Inspect coolant
level
in the coolant reserve tank and radiator. Inspect system for leaks.
(5) Inspect
heater
door
controls.
Refer to Group 24, Heating and
Air Conditioning.

GAUGE
READING HIGH. NO PRESSURE BLOW OFF FROM RADIATOR PRESSURE CAP OR STEAM FROM
COOLANT
RESERVE
TANK.
X

(1)
Verify
gauge reading. Is a high
temperature
reading indi­
cated?

(2) Gauge reading at "H"
without
signs
of boiling.
(3) Low coolant
level
in radiator and coolant reserve tank.
MAXIMUM
HOT

WEATHER

HEAVY
LOAD

MAXIMUM
UP

TO
TOP AMBIENT High Gauge
Reading
— Hot
Weather
—
Heavy
Load

(1) Compare gauge reading to High Gauge Reading Illustration
above.
(2) Inspect for grounded
gauge,
sending
unit
or circuit. Refer to

Group
8, Electrical.
(4) Coolant
level
in radiator
is
low.
But
not low in coolant reserve tank.
(5) Test coolant
freeze
point. (3) a-
b — (4) a-
b —
d —
(5) a- (6) Ensure proper coolant flow.
(6) a-
b —
Fill
to
full.

Inspect for leaks in system and
repair

as
necessary.
Ensure
radiator pressure cap was shut
tight.
Verify
proper operation of the radiator

cap
upper and lower
seals.
Fill
to
full.

Inspect for leaks in the system and
repair

as
necessary.
Inspect for leaks in the coolant reserve
tank to radiator hose.
Verify
proper operation of the radiator cap
upper and lower
seals.

Adjust coolant solution to
50/50
mixture
of
anti-freeze
and
water.
Refer to Coolant
in this group. If a reading is not recorded or below - 50.
the
mixture
is too rich. Clean system and
fill

with
a
50/50
mixture
of
anti-freeze
and
water.
Refer to Coolant in this group.
With the thermostat open and a slight amount
of coolant removed, inspect for coolant flow
through the radiator at the
filler
neck opening. Determine reason for lack of coolant flow
and
repair
as necessary.
J9107-22

•

COOLING
SYSTEM
7-11 DIESEL COOLING SYSTEM DIAGNOSIS-CONTINUED
Condition and Chocks
Diagnosis

(7) Other possible
causes.
(7) a — If
symptom
occurs
during high speed operation inspect for

plugged
air
inlet
side of the radiator or condenser,

plugged
radiator core tubes, add on
A/C
package without
proper radiator, engine not operating
within
specifications,

dragging
brakes,
trailer
towing or
hill
climbing, or an insect screen.
b — If
symptom
occurs
during
high
or low speed operation inspect for: thermostat being stuck
partially
open if ambient

temperature
is
below 70°F
and
the vehicle
has
high

mileage,
plugged
air
inlet
side of the radiator or
condenser, add on
A/C
with
incorrect radiator.

c
— If
symptom
occurs
during low
speed
operation only, inspect the radiator fan drive. Repair
as
necessary.

TEMPERATURE
GAUGE
READS
HOT.
PRESSURE
CAP VENTS
RESULTING
IN
STEAM
AND COOLANT
TRANSFER
TO

COOLANT
RESERVE
TANK.

(1)
Coolant
level
low in radiator and coolant reserve tank. (1) a —
Fill
cooling
system
and vent trapped air.
b — Inspect for leaks. Repair as necessary.

c
—
Ensure
that
pressure cap
is
completely shut and
seals.

d
— If
level
is low in radiator but normal in the coolant reserve tank, check the
filler
cap to coolant reserve
bottle
connection and pressure cap seal.
(2) Test coolant
freeze
point. (2) Adjust coolant to 50/50 mix of
anti-freeze
and
water.
Refer to

Coolant
section
in this group.
(3)
Ensure
coolant
is
flowing through system. (3) a — With the coolant
level
low and the thermostat open, check
for coolant flow through the radiator at the
filler
neck.
b — If a
metal
cracking
sound
is
heard, inspect for core sand restricting coolant flow through the
water
jacket
and/or a

faulty
cylinder head casting.
(4) Thermostat stuck in the
closed
position (prevalent in cold ambient temperatures). (4) Replace thermostat if found to be stuck in
closed
position. Refer
to the Thermostat Testing section in this group.
(5) Cylinder head gasket leak. (5) Inspect for leaking cylinder head
gasket
with
a commercially
available Block Leak Tester.
J9007-57

7
- 12
COOLING
SYSTEM

• DIESEL COOLING SYSTEM DIAGNOSIS-CONTINUED

CONDITION
AND
CHECKS
DIAGNOSIS

TEMPERATURE GAUGE
IS
INCONSISTENT,
CYCLES
AND/OR
IS
ERRATIC.
J
(1)
Is
cycle
normal.

(a)
Normal
Gauge
Reaction
to Thermostat
Cycle.
Normal
Gauge
Reaction
to Thermostat
Cycle.

MID

(b)
Normal
Gauge
Reaction
at
Stop
After
Heavy
Use.
(c)
Hot
Water
Build-Up
Is
Normal
at
Stop
after
Heavy

Use.

(2)
Is
coolant
in
radiator
low
(air
will
build
up in
the
cooling
system and cause
the
thermostat
to
open
late). (2)

Fill
system,
vent
trapped
air
and
check
for
leaks.

(3)
Is
a
cylinder
head
gasket
leak
allowing
exhaust
gas
to
enter
cooling
system
(exhaust
gas
building
up in
the

cooling
system
will
cause
the
thermostat
to
open
late).
(3)

a
—
Test
for
leaking
cylinder
gasket
leak
with
a

commercially
available
Block
Leak
Tester,

b
—
Check
for
coolant
in
enaine
oil.

c
—
Inspect
for
white
steam
from
exhaust
system.

(4)
Water
pump
impeller
loose
on
shaft.
Loose
accessory
drive
belt. (4)

Repair or
replace
as
necessary.

(5)
Air
leak
on
the
suction
side
of the
water
pump
(allows
air
to
build
up in
cooling
system causing
thermostat
to
open
late). (5)

Find
leak
and
repair.

PRESSURE
CAP
VENTS
TO
ATMOSPHERE
AND
COOL­

ANT
RESERVE
TANK.
TEMPERATURE GAUGE
READ­

ING ABOVE NORMAL
BUT NOT
HIGH.

(1)
Test
radiator
pressure
cap
relief
pressure.
Refer
to
Radiator
Pressure
cap
section
in
this
group.
ID

Replace
cap
if relief
pressure
is
lower
than
14
psi.
COOLANT
LOSS
VISIBLE
ON
GROUND BELOW VEHI­

CLE,
BUT NO
PRESSURE
CAP
BLOW
OFF.

(1)
Inspect
system
for
leaks.
(1)
Repair
as
necessary.
J9107-23

•
COOLING SYSTEM 7-13
DIESEL COOLING SYSTEM DIAGNOSIS-CONTINUED

CONDITION
AND
CHECKS
DIAGNOSIS

COOLANT
LOSS
PAST
PRESSURE
CAP
TOP
SEAL,

VISIBLE
ON
RADIATOR
FILLER
NECK.
(1)
With
normal gauge reading. (1) a — Pressure cap not installed
tightly.

b — Pressure cap top seal leaks.

c
— Pressure cap diaphragm bowed.

d
— Damaged
radiator
filler
neck.
e — Pressure cap top seal out of position.
(2)
With
high or low gauge reading on new vehicle. (2) a — Kinked coolant reserve system hose.
(2)
With
high or low gauge reading on new vehicle.
b — Coolant reserve system
tank
plastic
tube
plugged.

c
— Pressure cap seal out of position.

DETONATION
OR
PREIGNITION.
NOT
CAUSED
BY
IGNI­

TION OR
ENGINE
CONDITIONS.

(1)
Check engine coolant
freeze
point.
If the
tester
does
not
regis­
(1) a — Adjust coolant solution to
50/50
water

ter a reading or if the reading is below 50°F, inspect
ethyl­
ethylene-glycol
mixture.

ene-glycol/
water
ratio.
A 100
percent
solution of
ethylene-
b — If 100
percent
ethylene-glycol
solution is found
glycol
in
the
system
causes
the engine
to
run
hotter
and
possi­
in system,
clean
and flush system
before

bly overheat.
replacing
with
50/50
mixture
of

ethylene-glycol
and
water.

COOLING
SYSTEM
HOSES
COLLAPSE
ON
COOLDOWN.
(1) Inspect pressure cap
vent
valve. (1) a — Gasket swell can
prevent
valve
from
opening.
b — Replace pressure cap.
(2) Coolant reserve
tank
hose plugged or kinked. (2) Repair as necessary.
(3) Inside of pressure cap plugged. (3) Clean cap or
replace
if necessary.

COOLING
SYSTEM
SUSPECTED
AS
CAUSE
OF
INADE­
QUATE
AIR CONDITIONING
SYSTEM
PERFORMANCE.

(1) Inspect for plugged
radiator
and/or condenser. (D Clean
with
low pressure
water
from
fan side.
(2) Inspect for
missing
air
seals
in the
recirculating
air path. (2) Repair
as
necessary.

EXCESSIVE
FAN
NOISE

(1)
Inspect for loose or
bent
fan blades. (1) Replace fan.
(2) Inspect clearance
between
fan and
adjacent
part.
(2) Repair or
replace
as necessary.
(3) Inspect
radiator
and condenser for incoming air obstructions. (3) Clean air path
with
low pressure
water
from
fan side.
(4) Inspect
viscous
fan drive. (4) Replace if
viscous
drive
does not
operate
properly.

HEAT
ODOR

(1)
Was
temperature
gauge reading high? (1) If
YES,
refer
to
GAUGE
READING
HIGH.
If
NO,
refer
to
steps

2, 3, and 4.
(2) Are all
heat
shields in place? (2) If
YES,
refer
to steps 3 and 4. If NO,
repair
as
required.

(3)
Is
the air side of the
heat
exchanger plugged? (3) Clean as necessary.
(4) Engine running rich causing
catalytic
converter
to overheat. (4) Repair
as
necessary.

POOR
DRIVEABILITY.
SUSPECT
THERMOSTAT FAILED
IN OPEN POSITION.

(1)
Thermostat stuck in open position? 01 Replace thermostat. ._ _0 .
Jy
107-24

7 - 14 COOLING SYSTEM
• DIESEL COOLING SYSTEM DIAGNOSIS-CONTINUED

CONDITION
AND
CHECKS
DIAGNOSIS

POOR
HEATER
PERFORMANCE.
SUSPECT

THERMOSTAT
FAILED
IN
OPEN
POSITION.

(1)
Does
gauge
read
low?
(1) If
YES,
replace thermostat. If
NO,
inspect
the auxiliary

heater
vacuum
water
valve.
The valve
should
be open
except
when
the climate
controls
are
OFF
or in the
MAX

A/C
mode.
(2)
Is
coolant
level
low?
(2)
Fill
cooling
system
and
inspect
for
leaks.
Repair
as
neces­

sary.

(3) Thermostat failed in open
position?
(3) If
YES,
replace thermostat. If
NO,
inspect
the auxiliary

heater
vacuum
water
valve.
The valve
should
be open
except
when
the climate
controls
are
OFF
or in the
MAX

A/C
mode.
J9107-25

•

COOLING SYSTEM
7 - 15
SERVICE
PROCEDURES

INDEX
page
Coolant
26
Coolant Reserve/Overflow System
30

Cooling System Cleaning/Reverse Flushing
28

Cooling System Fan—Diesel Engine
. 37

Cooling System
Fan—Gas
Engines
36

Cooling System
Hoses
34
Draining Cooling System
27

Pressure
Testing
Radiator
Caps
............. 32

Radiator Pressure
Cap 31

Radiators
32

Refilling
the
Cooling System
28

WATER PUMPS—EXCEPT DIESEL
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
radiator core, cooling system hoses and heater core.
The pump is driven from the engine crankshaft by a drive belt. The water pump impeller is pressed onto the rear
of a shaft that rotates in a bearing pressed into the
water pump body. The body has a small hole for ven­
tilation. The water pump seals are lubricated by an­
tifreeze in the coolant mixture. Additional lubrication is not necessary. A quick test to determine if pump is working is to
check if heater warms properly. A defective water
pump will not be able to circulate heated coolant
through the long heater hose to the heater core. The water pump on all models can be removed
without discharging the air conditioning system (if equipped).
REMOVAL The water pump on all gas powered engines is
bolted directly to the engine timing chain case/cover.
A gasket is used as a seal between the water pump
and timing chain case/cover.
If water pump is replaced because of bearing/shaft
damage or leaking shaft seal, the mechanical cooling
fan assembly should also be inspected. Inspect for fa­ tigue cracks, loose blades or loose rivets that could
have resulted from excessive vibration. Replace fan if any of these conditions are found. Also check condi­
tion of the thermal viscous fan drive. Refer to Vis­
cous Fan Drive in this group. (1) Disconnect negative battery cable from battery.
(2) Drain cooling system. Refer to Draining Cool­
ing System in this group. Do not waste reusable coolant. If solution is clean,
drain coolant into a clean container for reuse.
(3)
Disconnect throttle cable from clip at top of fan
shroud.
page

Testing
Cooling System
for
Leaks
. 29

Thermostat
22

Transmission
Oil
Cooler—Diesel
35

Transmission
Oil
Cooler—Except Diesel
35

Transmission Oil-To-Air Cooler
36
Viscous
Fan
Drive
38

Water
Pump
Bypass
Hose—All
Gas
Powered
Engines
.............................. 19

Water
Pumps—5.9L Diesel
18

Water
Pumps—Except Diesel
15
(4) Unsnap coolant reserve/overflow tank (up and
out) from the T-slots on side of fan shroud (Fig. 1) and lay aside. Do not disconnect hose or drain cool­
ant from tank.
(5) Remove the fan shroud from the radiator. Do
not remove shroud from vehicle at this time.
FAN

SHROUD
J9107-67

Fig.
1 Fan
Shroud—Except
Diesel

(6) Remove upper radiator hose at radiator. Special
Clamp Tool number 6094 (Fig. 2) may be used to re­
move the constant tension clamps.
(7) The thermal viscous fan drive is attached
(threaded) to the water pump hub shaft (Fig. 3). Re­
move the fan/fan drive assembly from water pump by
turning the mounting nut counterclockwise (as viewed from front). Threads on the fan drive are RIGHT HAND. A Snap-On 36 MM Fan Wrench (number SP346 from Snap-On Cummins Diesel Tool
Set number 2017DSP) can be used. Place a bar or
screwdriver between the water pump pulley bolts (Fig. 3) to prevent the pulley from rotating.
If water pump is being replaced, do not unbolt fan
blade assembly (Fig. 3) from the thermal control fan drive.

7 - 16
COOLING
SYSTEM

•

HOSE
CLAMP
HOSE

J9207-36
Fig.
2
Hose
Clamp
Tool
(8) Remove fan blade/fan drive and fan shroud as
an assembly from vehicle. After removing fan blade/fan drive assembly, do
not place the thermal viscous fan drive in the hori­
zontal position. If stored horizontally, the silicone
fluid in the viscous drive could drain into its bearing assembly and contaminate the bearing lubricant.
Do not remove the water pump pulley bolts at this

time.
FAN
BLADE
WATER WATER
PUMP

VISCOUS
FAN
DRIVE
J9307-32

Fig.
3 Fan Blade and
Viscous
Fan Drive—Typical (9) Remove accessory drive belt as follows: The
drive belt is equipped with a spring loaded automatic
tensioner (Figs. 4 or 5).
3.9L/5.2L/5.9L LDC-Gas Engines: Relax the tension
from the belt by rotating the tensioner clockwise (as
viewed from front) (Fig. 4). When all belt tension has
been relaxed, remove accessory drive belt. 5.9L HDC-Gas Engines: Relax the tension from the belt by rotating the tensioner counterclockwise (as
viewed from front) (Fig. 5). When all belt tension has
been relaxed, remove accessory drive belt.
Fig.
4 Belt Tensioner—3.9L/5.2L/5.9L
LDC-Gas

Engine

Fig.
5 Belt Tensioner—5.9L
HDC-Gas
Engine
(10) Remove the four water pump pulley-to-water
pump hub bolts (Fig. 3) and remove pulley from ve­ hicle.
(11) Remove the lower radiator hose and heater
hose from water pump.

•

COOLING
SYSTEM
7-17 (12) Loosen heater hose coolant return tube
mounting bolt (Figs. 6 or 7) and remove tube from
water pump. Discard the old tube O-ring.

Fig.
6 Coolant Return Tube—3.9L/5.2L/5.9L
LDC-Gas
Engine

Fig.
7 Coolant Return Tube—5.9L
HDC-Gas
Engine
(13) Remove the seven water pump mounting bolts
(Fig. 8). (14) Loosen the clamp at the water pump end of
bypass hose (Fig. 3). Slip the bypass hose from the water pump while removing pump from vehicle. Do not remove the clamp from the bypass hose.
Fig.
8
Water
Pump
Bolts—Typical
(15) Discard old gasket.

CAUTION:
Do not pry the
water
pump
at timing

chain
case/cover.
The machined
surfaces
may be

damaged
resulting in
leaks.

INSPECTION
Replace water pump assembly if it has any of the
following conditions: • The body is cracked or damaged
• Water leaks from the shaft seal. This is evident by
traces of coolant below the vent hole • Loose or rough turning bearing. Also inspect ther­mal fan drive
• Impeller rubs either the pump body or timing
chain case/cover

INSTALLATION
(1) Clean gasket mating surfaces. (2) Using a new gasket, install water pump to en­
gine as follows: Guide water pump nipple into bypass
hose as pump is being installed. Install water pump bolts (Fig. 8). Tighten water pump mounting bolts to 40 N-m (30 ft. lbs.) torque.
(3) Spin water pump to be sure that pump impeller
does not rub against timing chain case/cover.
(4) Install a new O-ring to the heater hose coolant
return tube (Figs. 6 or 7). Coat the new O-ring with antifreeze before installation.
(5) Install coolant return tube and its mounting
bolt to engine (Figs. 6 or 7). Be sure the slot in tube bracket is bottomed to mounting bolt. This will prop­ erly position return tube.
(6) Connect radiator lower hose to water pump.
(7) Connect heater hose and hose clamp to coolant
return tube.
(8) Install water pump pulley. Tighten bolts to 27
N*m (20 ft. lbs.) torque. Place a bar or screwdriver
between water pump pulley bolts (Fig. 3) to prevent pulley from rotating.