1993 DODGE TRUCK heater

•

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.

7 - 18
COOLING
SYSTEM

• (9) Relax tension from automatic belt tensioner

(Figs.
4 or 5). Install drive belt.

CAUTION:
When
installing
the
serpentine
accessory

drive
belt, belt
must
be
routed
correctly.
If not, en­

gine
may
overheat
due to
water
pump
rotating
in

wrong
direction.
Refer
to
(Figs,
i, 10 or 11) for
cor­
rect
belt
routing.
The
correct
belt with
correct

length
must
be
used.

*IF
VEHICLE
IS NOT
EQUIPPED
WITH
POWER
STEERING,
THIS
WILL
BE
AN
IDLER
PULLEY.
J9307-26
Fig.
9 Belt Routing—3.9U5.2L/5.9L
LDC-Gas
Engine

AUTOMATIC
TENSIONER
AUTOMATIC

TENSIONER

J9307-56

Fig.
11 Belt Routing—5.9L
HDC-Gas
Engine—Without
A/C (10) Position fan shroud and fan blade/viscous fan
drive assembly to vehicle as a complete unit. (11) Install fan shroud.
(12) Install fan blade/viscous fan drive assembly to
water pump shaft.
(13) Fill cooling system. Refer to Refilling Cooling
System in this group. (14) Connect negative battery cable.
(15) Start and warm the engine. Check for leaks.

WATER
PUMPS—5.9L
DIESEL
The diesel engine water pump draws coolant from
radiator outlet and circulates it through engine,
heater core and back to radiator inlet. The crank­ shaft pulley drives the water pump via a serpentine
drive belt (Fig. 12). An automatic belt tensioner (Fig. 12) is used to prevent the belt from slipping.
REMOVAL (1) Disconnect the negative battery cable at bat­
tery. (2) Drain cooling system. Refer to Draining Cool­
ing System in this section.
(3) Remove the accessory drive belt. Refer to the
Engine Accessory Drive Belt section of this group. (4) Remove water pump mounting bolts (Fig. 13).
(5) Clean water pump sealing surface on cylinder
block.
J9307-55

Fig.
10 Belt Routing—5.9L
HDC-Gas
Engine-With

A/C
INSTALLATION

(1) Install new O-ring seal in groove on water
pump (Fig. 14). (2) Install water pump. Tighten mounting bolts to
24 N-m (18 ft. lbs.) torque.

•

COOLING
SYSTEM
7 - 21

Fig.
19 Belt Tensioner—5.9L
HDC-Gas
Engine
(11) Remove heater hose coolant return tube
mounting bolt (Figs. 20 or 21) and remove tube from
engine. Discard the old tube O-ring,
Fig.
20 Coolant Return Tube-3.9U5.2U5.9L LDC-

Gas
Engine
(12) Remove bracket-to-intake manifold bolts
(number 1 and 2 Fig. 17).
(13) Remove remaining bracket-to-engine bolts

(Figs.
22 or 23). (14) Lift and position generator and A/C compres­
sor (along with their common mounting bracket) to
gain access to bypass hose. A block of wood may be
Fig.
21 Coolant Return Tube—5.9L
HDC-Gas
Engine

Fig.
22 Bracket Bolts-3.9U5.2U5.9L
LDC-Gas
Engine
used to hold assembly in position.
(15) Loosen and position both hose clamps to the
center of bypass hose. Special Clamp Tool number
6094 (Fig. 16) may be used to remove the constant
tension clamps. Remove hose from vehicle.

INSTALLATION
(1) Position bypass hose clamps to the center of

hose.

7 - 22
COOLING
SYSTEM

•

Fig.
23 Bracket
Bolts—5.9L
HDC-Gas Engine
(2) Install bypass hose to engine.
(3) Secure both hose clamps.
(4) Install generator-A/C mounting bracket assem­
bly to engine. Tighten bolts (number 1 and 2 Fig. 17)
to 54 Nnn (40 ft. lbs.) torque. Tighten bracket mount­ ing bolts (Figs. 22 or 23) to 40 N-m (30 ft. lbs.)
torque.
(5) Install a new O-ring to the heater hose coolant
return tube (Figs. 20 or 21). Coat the new O-ring
with antifreeze before installation. (6) Install coolant return tube and its mounting
bolt to engine (Figs. 20 or 21). (7) Connect throttle body control cables.
(8) Install oil dipstick mounting bolt.
(9) 3.9L/5.2L/5.9L LDC-Gas: Install idler pulley.
Tighten bolt to 54 Nnn (40 ft. lbs.) torque. 5.9L HDC-Gas: Install automatic belt tensioner
assembly to mounting bracket. A dowel pin is located
on back of tensioner (Fig. 24). Align this to dowel
hole (Fig. 25) in tensioner mounting bracket. Tighten
bolt to 41 N-m (30 ft. lbs.). (10) Install drive belt. Refer to Belt Removal/In­
stallation in the Engine Accessory Drive Belt section
of this group.

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 belt routing.
The
correct belt

with the
correct length must
be
used.

(11) Install air cleaner assembly.
BELT TENSIONER
DOWEL PIN
J9307-63

Fig.
24 Tensioner
Dowel
Pin—5.9L
HDC-Gas Engine Fig.
25 Tensioner
Mounting
Bracket
Dowel

Hote—5.9L
HDC-Gas Engine

(12) Install upper radiator hose to radiator.
(13) Connect throttle cable to clip at radiator fan
shroud.
(14) Connect wiring harness to A/C compressor. (15) Fill cooling system. Refer to Refilling Cooling
System in this group.
(16) Start and warm the engine. Check for leaks.

THERMOSTAT
GENERAL
INFORMATION
The thermostat on all gas powered engines is lo­
cated beneath the thermostat housing at the front of
the intake manifold (Fig. 26). The thermostat has an air bleed notch.
The thermostat of the 5.9L diesel engine is located
in the thermostat housing at front of cylinder head.
This is on exhaust manifold side of engine (Fig. 27). The thermostat is a wax pellet driven, reverse pop­
pet choke type. The wax pellet is located in a sealed container at the spring end of the thermostat. When
heated, the pellet expands, overcoming closing spring

•

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.

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).