1993 DODGE TRUCK coolant temperature

7 - 8
COOLING
SYSTEM

COOLING SYSTEM DIAGNOSIS (EXCEPT DIESEL)—CONTINUED

Condition and Check
Diagnosis

PRESSURE
CAP
VENTS
TO
ATMOSPHERE
AND COOLANT

RESERVE
TANK.
TEMPERATURE
GAUGE
READING
ABOVE

NORMAL
BUT NOT HIGH.
(1) Test radiator pressure cap
relief
pressure. Refer to Radiator Pressure cap section in this group. (1) Replace cap if
relief
pressure is lower than 14 psi.

COOLANT
LOSS
VISIBLE
ON
GROUND
BELOW
VEHICLE,
BUT
NO
PRESSURE
CAP
BLOW
OFF.
(1) Inspect
system
for leaks. (1) Repair as necessary.

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.
b — Coolant reserve
system
tank
plastic
tube
plugged,

c
— Pressure cap seal out of position.

DETONATION
OR
PREIGNITION.
NOT
CAUSED
BY IGNITION

OR
ENGINE
CONDITIONS.

(1) Check engine coolant
freeze
point. If the
tester
does
not register a reading or if
the
reading
is
below
50°F,
inspect
ethylene-

glycol/water
ratio.
A 100
percent
solution of ethylene-glycol in
the
system
causes
the engine to run
hotter
and
possibly
overheat. (1) a — Adjust coolant solution to
50/50
water
ethylene-glycol

mixture.

b — If 100
percent
ethylene-glycol solution
is
found in system, clean and flush
system
before
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
INADEQUATE

AIR
CONDITIONING
SYSTEM
PERFORMANCE.

(1) Inspect for plugged radiator and/or condenser. (1) 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) If 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
DRIVEABIUTY.
SUSPECT
THERMOSTAT
FAILED
IN
OPEN
POSITION.

(1) Check On-Board
Diagnostics.
Is code 17 set in memory? (1) If
YES,
replace thermostat. If NO,
refer
to the appropriate
Driveability Manual.

J9007-59

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

•

COOLING SYSTEM
7 - 23

•THERMOSTAT

MACHINED GROOVE
J9207-14
Fig.
26
Thermostat—
Gas Engines
Fig.
27 Thermostat—5.9L Diesel—Typical
tension and water pump pressure to force the valve
to open. Coolant leakage into the pellet container
will cause the thermostat to fail in the open position.
Thermostats very rarely stick. Do not attempt to free a thermostat with a prying device.
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 longer engine
warmup time, unreliable warmup performance, in­
creased exhaust emissions and crankcase condensa­
tion that can result in sludge formation.

CAUTION:
Do not operate an engine without a
ther­
mostat,
except for
servicing
or
testing.
THERMOSTAT OPERATION-EXCEPT DIESEL
The thermostat controls the operating temperature
of the engine by controlling the amount of coolant
flow to the radiator. The thermostat is closed below 88°C (192°F). When the coolant reaches this temper­
ature, the thermostat begins to open, allowing cool­
ant flow to the radiator. This provides quick engine
warm-up and overall temperature control. The ther­
mostat is designed to provide a minimum engine op­ erating temperature of 88 to 93°C (192 to 199°F). It
should be fully open for maximum coolant flow dur­
ing operation in hot ambient temperatures of approx­
imately 104°C (220°F). Above 104°C (220°F), coolant
temperature is controlled by the radiator, fan and ambient temperature.
An arrow plus the word UP is stamped on the
front flange next to the air bleed. The words TO RAD are stamped on one arm of the thermostat.
They indicate the proper installed position.
TESTING-ALL ENGINES The computer On-Board Diagnostics include a
mode for a thermostat open-too-soon failure condi­
tion. The Malfunction Indicator Light (formerly called the Check Engine Light) will not be lit by an
open-too-soon condition. But, if it has failed open, a
Diagnostic Trouble Code (DTC) number 17 will be
set. Do not change a thermostat for lack of heat as
indicated by the instrument panel gauge or heater
performance unless a DTC number 17 is present. Re­
fer to the Diagnosis section of this group for other
probable causes.
The more common type of thermostat failure, usu­
ally found on high milage vehicles, is a thermostat
failed in the shut position. The temperature gauge (if equipped) will give an indication of this condition.
Depending upon length of time that vehicle is oper­
ated, pressure cap may vent. This will expel steam
and coolant to coolant reserve/overflow tank and to
surface below vehicle. Refer to the Diagnosis section
of this group. Also refer to the DRB II diagnostic
scan tool.
On-Board Diagnostics for the 5.9L diesel engine
can be obtained through the DRB II scan tool.
Vehicles equipped with a 5.9L diesel engine do not
have the DTC number 17 malfunction indicator lamp (check engine lamp) feature.
REMOVAL-ALL GAS POWERED ENGINES

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.

•

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).