2003 DODGE RAM Heater core

DESCRIPTIONÐCOOLING SYSTEM FLOW -
5.9L DIESEL
The diesel engine cooling system consists of :
²Cross-flow radiator
²Belt driven water pump
²Belt driven mechanical cooling fan
²Electronic viscous fan drive
²Fan shroud
²Radiator pressure cap²Vertically mounted thermostat
²Coolant reserve/recovery system
²Transmission oil cooler
²Coolant
Coolant flow circuits for the 5.9L diesel engine are
shown in (Fig. 3).
Fig. 1 Engine Cooling System Flow - 3.7L/4.7L
1 - LH CYL. HEAD
2 - BLEED
3 - THERMOSTAT LOCATION
4 - RH CYL. HEAD
5 - RH BANK CYL. BLOCK6 - LH BANK CYL. BLOCK
7 - COOLANT TEMP. SENSOR
8 - FROM HEATER CORE
9 - TO HEATER CORE
7 - 2 COOLINGDR
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
TEMPERATURE GAUGE READS
HIGH. COOLANT MAY OR MAY
NOT BE LEAKING FROM
SYSTEMNOTE:
Information on dash cluster is
displayed based on broadcast data
from ECM. DTC will be set for
engine sensor circuit concern.1. Vehicle overloaded, high ambient
(outside) temperatures with A/C
turned on, stop and go driving or
prolonged operation at idle speeds.1. Temporary condition, repair not
required. Notify customer of vehicle
operation instructions located in
Owners Manual.
2. Temperature gauge not
functioning correctly.2. Check cluster (Refer to 8 -
ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND
TESTING)
3. Air trapped in cooling system 3. Drain cooling system (Refer to 7 -
COOLING - STANDARD
PROCEDURE) and refill (Refer to 7
- COOLING - STANDARD
PROCEDURE)
4. Radiator cap faulty. 4. Replace radiator cap.
5. Plugged A/C or radiator cooling
fins.5. Clean all debris away from A/C
and radiator cooling fins.
6. Coolant mixture incorrect. 6. Drain cooling system (Refer to 7 -
COOLING - STANDARD
PROCEDURE) refill with correct
mixture (Refer to 7 - COOLING -
STANDARD PROCEDURE).
7. Thermostat stuck shut. 7. Inspect and test thermostat.
Replace thermostat if necessary.
8. Bug screen or winter front being
used.8. Remove bug screen or winter
front.
9. Electronically controlled viscous
fan drive not operating properly.9. Check viscous fan (Refer to 7 -
COOLING/ENGINE/FAN DRIVE
VISCOUS CLUTCH - DIAGNOSIS
AND TESTING)
10. Cylinder head gasket leaking. 10. Check for leaking head gaskets
(Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).
11. Heater core leaking. 11. Replace heater core.
12. Cooling system hoses leaking. 12. Tighten clamps or Replace
hoses.
13. Brakes dragging. 13. Check brakes. (Refer to 5 -
BRAKES/HYDRAULIC/
MECHANICAL - DIAGNOSIS AND
TESTING)
14. Accessory drive belt. 14. Inspect. Replace as necessary.
15. Water Pump. 15. Inspect and replace as
necessary.
7 - 8 COOLINGDR
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
10. Radiator or A/C condenser
fins are dirty or clogged.10. Remove insects and debris. (Refer to
7 - COOLING - STANDARD
PROCEDURE).
11. Radiator core is corroded or
plugged.11. Have radiator re-cored or replaced.
12. Fuel or ignition system
problems.12. Refer to 14 - Fuel System or 8 -
Electrical for diagnosis and testing
procedures.
13. Dragging brakes. 13. Check and correct as necessary.
(Refer to 5 - BRAKES - DIAGNOSIS AND
TESTING) for correct procedures.
14. Bug screen or cardboard is
being , reducing airflow.14. Remove bug screen or cardboard.
15. Thermostat partially or
completely shut.15. Check thermostat operation and
replace as necessary. (Refer to 7 -
COOLING/ENGINE/ENGINE COOLANT
THERMOSTAT - REMOVAL) .
16. Viscous fan drive not
operating properly.16. Check fan drive operation and replace
as necessary. (Refer to 7 - COOLING/
ENGINE/FAN DRIVE VISCOUS CLUTCH
- REMOVAL).
17. Cylinder head gasket
leaking.17. Check for cylinder head gasket leaks.
(Refer to 7 - COOLING - DIAGNOSIS
AND TESTING).
18. Heater core leaking. 18. Check heater core for leaks. (Refer to
24 - HEATING & AIR CONDITIONING/
PLUMBING - DIAGNOSIS AND
TESTING). Repair as necessary.
DRCOOLING 7 - 13
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
INADEQUATE HEATER
PERFORMANCE.
THERMOSTAT FAILED IN
OPEN POSITION1. Has a Diagnostic trouble
Code (DTC) been set?1. (Refer to 25 - EMISSIONS CONTROL -
DESCRIPTION) for correct procedures
and replace thermostat if necessary
2. Coolant level low 2. (Refer to 7 - COOLING - DIAGNOSIS
AND TESTING).
3. Obstructions in heater
hose/fittings3. Remove heater hoses at both ends and
check for obstructions
4. Heater hose kinked 4. Locate kinked area and repair as
necessary
5. Water pump is not pumping
water to/through the heater core.
When the engine is fully warmed
up, both heater hoses should be
hot to the touch. If only one of
the hoses is hot, the water
pump may not be operating
correctly or the heater core may
be plugged. Accessory drive belt
may be slipping causing poor
water pump operation.5. (Refer to 7 - COOLING/ENGINE/
WATER PUMP - REMOVAL). If a slipping
belt is detected, (Refer to 7 - COOLING/
ACCESSORY DRIVE/DRIVE BELTS -
DIAGNOSIS AND TESTING). If heater
core obstruction is detected, (Refer to 24 -
HEATING & AIR CONDITIONING/
PLUMBING/HEATER CORE - REMOVAL).
STEAM IS COMING FROM THE
FRONT OF VEHICLE NEAR
THE GRILL AREA WHEN
WEATHER IS WET, ENGINE IS
WARMED UP AND RUNNING,
AND VEHICLE IS STATIONARY.
TEMPERATURE GAUGE IS IN
NORMAL RANGE1. During wet weather, moisture
(snow, ice or rain condensation)
on the radiator will evaporate
when the thermostat opens. This
opening allows heated water
into the radiator. When the
moisture contacts the hot
radiator, steam may be emitted.
This usually occurs in cold
weather with no fan or airflow to
blow it away.1. Occasional steam emitting from this
area is normal. No repair is necessary.
COOLANT COLOR 1. Coolant color is not
necessarily an indication of
adequate corrosion or
temperature protection. Do not
rely on coolant color for
determining condition of coolant.1. (Refer to LUBRICATION &
MAINTENANCE/FLUID TYPES -
DESCRIPTION). Adjust coolant mixture as
necessary.
COOLANT LEVEL CHANGES IN
COOLANT RESERVE/
OVERFLOW TANK.
TEMPERATURE GAUGE IS IN
NORMAL RANGE1. Level changes are to be
expected as coolant volume
fluctuates with engine
temperature. If the level in the
tank was between the FULL and
ADD marks at normal operating
temperature, the level should
return to within that range after
operation at elevated
temperatures.1. A normal condition. No repair is
necessary.
7 - 16 COOLINGDR
COOLING (Continued)

STANDARD PROCEDURE
STANDARD PROCEDURE - COOLANT LEVEL
CHECK
NOTE: Do not remove radiator cap for routine cool-
ant level inspections. The coolant level can be
checked at coolant recovery bottle or the coolant
degas bottle.
WARNING: DO NOT REMOVE OR LOOSEN THE
RADIATOR CAP WITH THE COOLING SYSTEM HOT
AND UNDER PRESSURE. SERIOUS BURNS FROM
COOLANT OR HIGH PRESSURE STEAM CAN
OCCUR.
The 5.9L, 5.9L Diesel, and 8.0L engine coolant
reserve / overflow system provides a quick method for
determining the coolant level without removing the
radiator pressure cap. With the engine at normal
operating temperature and idling, observe the level
of the coolant on the external level indicator on the
side of the coolant reserve / overflow bottle. The cool-
ant level should be between the MIN and MAX
marks. If the coolant is below the MIN mark, add a
50/50 mixture of antifreeze and water to the bottle
until the level reaches the MIN mark.Do Not Over-
fill the bottle by adding fluid above the MAX
line.This may cause coolant to spill onto the ground
during subsequent vehicle operation.
The 3.7L/4.7L/5.9L engine coolant degas system
provides a quick method for determining the coolant
level with out removing the radiator pressure cap.
With a cold engine, observe the level of coolant in the
degas bottle. The level should be in the COLD FILL
RANGE.DO NOT OVERFILLthe bottle by adding
fluid above the COLD FILL RANGE. This may cause
coolant to spill onto the ground during subsequent
vehicle operation.
STANDARD PROCEDURE - COOLING SYSTEM
CLEANING/REVERSE FLUSHING
CLEANING
Drain the cooling system and refill with water. Run
the engine with the radiator cap installed until the
upper radiator hose is hot. Stop the engine and drain
the water from system. If the water is dirty, fill the
system with water, run the engine and drain the sys-
tem. Repeat this procedure until the water drains
clean.
REVERSE FLUSHING
Reverse flushing of the cooling system is the forc-
ing of water through the cooling system. This is doneusing 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
inlet and outlet. Attach a section of the radiator hose
to the radiator bottom outlet fitting and insert the
flushing gun. Connect a water supply hose and air
supply hose to the flushing gun.
CAUTION: Internal radiator pressure must not
exceed 138 kPa (20 psi) as damage to radiator may
result.
Allow the radiator to fill with water. When the
radiator is filled, apply air in short blasts. Allow the
radiator to refill between blasts. Continue this
reverse flushing until clean water flows out through
the rear of the radiator cooling tube passages.
REVERSE FLUSHING ENGINE
Drain the cooling system. Remove the thermostat
housing and thermostat. Install the thermostat hous-
ing. Disconnect the radiator upper hose from the
radiator and attach the flushing gun to the hose. Dis-
connect the radiator lower hose from the water pump
and attach a lead-away hose to the water pump inlet
fitting.
CAUTION: On vehicles equipped with a heater water
control valve, 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.
Connect the water supply hose and air supply hose
to flushing gun. Allow the engine to fill with water.
When the engine is filled, apply air in short blasts,
allowing the system to fill between air blasts. Con-
tinue until clean water flows through the lead away
hose.
Remove the lead away hose, flushing gun, water
supply hose and air supply hose. Remove the thermo-
stat housing and install the thermostat. Install the
thermostat housing with a replacement gasket. Refer
to Thermostat Replacement. Connect the radiator
hoses. Refill the cooling system with the correct anti-
freeze/water mixture. Refer to Refilling the Cooling
System.
CHEMICAL CLEANING
In some instances, use a radiator cleaner (Mopart
Radiator Kleen or equivalent) before flushing. This
will soften scale and other deposits and aid flushing
operation.
DRCOOLING 7 - 17
COOLING (Continued)

(5) Install the lower fan shroud into position and
verify the locking tabs have seated.
(6) Connect the battery negative cables.
NOTE:
Viscous Fan Drive Fluid Pump Out Requirement:
After installing a new viscous fan drive, bring the
engine speed up to approximately 2000 rpm and
hold for approximately two minutes. This will
ensure proper fluid distribution within the drive.
ENGINE BLOCK HEATER
DESCRIPTION
WARNING: DO NOT OPERATE ENGINE UNLESS
BLOCK HEATER CORD HAS BEEN DISCONNECTED
FROM POWER SOURCE AND SECURED IN PLACE.
THE POWER CORD MUST BE SECURED IN ITS
RETAINING CLIPS AND ROUTED AWAY FROM
EXHAUST MANIFOLDS AND MOVING PARTS.
An optional engine block heater is available with
all models. The heater is equipped with a power cord.
The cord is attached to an engine compartment com-
ponent with tie-straps. The heater warms the engine
providing easier engine starting and faster warm-up
in low temperatures. The heater is mounted in a core
hole of the engine cylinder block in place of a freeze
plug with the heating element immersed in engine
coolant. The 5.9L gas powered engine has the block
heater located on the right side of engine next to the
oil filter (Fig. 6). The 3.7L/4.7L gas powered engines
have the block heater located to the rear on the right
side of the engine (Fig. 7).
OPERATION
The heater warms the engine coolant providing
easier engine starting and faster warm-up in low
temperatures. Connecting the power cord to a
grounded 110-120 volt AC electrical outlet with a
grounded three wire extension cord provides the elec-
tricity needed to heat the element.
DIAGNOSIS AND TESTING Ð ENGINE BLOCK
HEATER
If the unit does not operate, possible causes can be
either the power cord or the heater element. Test the
power cord for continuity with a 110-volt voltmeter or
110-volt test light. Test heater element continuity
with an ohmmeter or a 12-volt test light.
CAUTION: To prevent damage, the power cord must
be secured in it's retainer clips and away from any
components that may cause abrasion or damage,
such as linkages, exhaust components, etc.
Fig. 6 Engine Block Heater - 5.9L
1 - FREEZE PLUG HOLE
2 - BLOCK HEATER
3 - SCREW
4 - POWER CORD (120V AC)
5 - HEATING COIL
6 - OIL FILTER
Fig. 7 Engine Block Heater - 3.7L/4.7L
1 - ENGINE BLOCK HEATER
7 - 42 ENGINEDR
RADIATOR FAN - 5.9L DIESEL (Continued)

(6) Remove the power steering cooler mounting
bolts and position the power steering cooler out of
the way.
(7) Disconnect the transmission cooler lines at the
transmission. The transmission cooler will remain on
the radiator and can be removed as an assembly.
(8) Remove the lower shroud assembly and the
electronic viscous fan wiring from the upper shroud
assembly.
(9) Remove the two radiator upper mounting bolts
(Fig. 36).
(10) Lift radiator straight up and out of engine
compartment. The bottom of the radiator is equipped
with two alignment dowels that fit into holes in the
lower radiator support panel. Rubber biscuits (insu-
lators) are installed to these dowels. Take care not to
damage cooling fins or tubes on the radiator and air
conditioning condenser when removing.
CLEANING
Clean radiator fins are necessary for good heat
transfer. The radiator and oil cooler fins should be
cleaned when an accumulation of debris has
occurred. With the engine cold, apply cold water and
compressed air to the back (engine side) of the radi-
ator to flush the radiator and/or oil coolers of debris.
INSPECTION
Inspect the radiator side tanks for cracks, broken
or missing fittings also inspect the joint where the
tanks seam up to the radiator core for signs of leak-
age and/or deteriorating seals.
Inspect radiator core for corroded, bent or missing
cooling fins. Inspect the core for bent or damaged
cooling tubes.
INSTALLATION
(1) Install rubber insulators to alignment dowels
at lower part of radiator.
(2) Lower the radiator into position while guiding
the two alignment dowels into lower radiator sup-
port. Different alignment holes are provided in the
lower radiator support for each engine application.
(3) Install two upper radiator mounting bolts.
Tighten bolts to 11 N´m (95 in. lbs.) torque.
(4) Connect both radiator hoses and install hose
clamps.
(5) Connect transmission cooler lines to radiator
tank. Inspect quick connect fittings for debris and
install until an audible ªclickº is heard. Pull apart to
verify connection.
(6) Position power steering cooler on the radiator
and tighten nuts to 8.5M´N (75 in. lbs.)
(7) Attach electronic viscous fan wiring to upper
shroud ands install lower shroud.
(8) Position coolant recover tank hose, washer bot-
tle hose and the positive battery cable into the clips
located on the top of the radiator.
(9) Install air box and turbocharger inlet hose.
Tighten clamps to 4 N´M (35 in. lbs.).
(10) Position heater controls tofull heatposition.
(11) Fill cooling system with coolant (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(12) Operate engine until it reaches normal tem-
perature. Check cooling system and automatic trans-
mission (if equipped) fluid levels.
RADIATOR PRESSURE CAP
DESCRIPTION
All cooling systems are equipped with a pressure
cap (Fig. 37). For 5.9L engines, the pressure cap is
located on top of the radiator outlet tank. For the
3.7L/4.7L engines, the pressure cap is located on top
of the coolant degas container. The cap releases pres-
sure at some point within a range of 97-to-124 kPa
(14-to-18 psi). The pressure relief point (in pounds) is
engraved on top of the 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 contains a spring-
Fig. 36 Fan Shroud MountingÐ5.9L Diesel Engine
1 - RADIATOR SUPPORT
2 - UPPER FAN SHROUD
3 - BOLTS (2)
4 - LOWER FAN SHROUD
5 - RADIATOR
7 - 60 ENGINEDR
RADIATOR - 5.9L DIESEL (Continued)

The pressure cap may test properly while posi-
tioned on tool 7700 (or equivalent). It may not hold
pressure or vacuum when installed on the radiator. If
so, inspect the radiator filler neck and radiator cap's
top gasket for damage. Also inspect for dirt or distor-
tion that may prevent the cap from sealing properly.
CAUTION: Radiator pressure testing tools are very
sensitive to small air leaks which will not cause
cooling system problems. 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 pressure cap to confirm that cap
needs replacement.
CLEANING
Use only a mild soap and water to clean the radi-
ator cap. Using any type of solvent may cause dam-
age to the seal in the radiator cap.
INSPECTION
Hold cap at eye level, right side up. The vent valve
(Fig. 39) at bottom of cap should closed. A slight
downward pull on the vent valve should open it. If
the rubber gasket has swollen and prevents vent
valve from opening, replace cap.
Hold cap at eye level, upside down. If any light can
be seen between vent valve and rubber gasket,
replace cap. A replacement cap must be the typedesigned for a coolant reserve/overflow 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.
WATER PUMP - 5.9L
DESCRIPTION
The water pump is located on the engine front
cover, and has an integral pulley attached (Fig. 40).
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
antifreeze in the coolant mixture. Additional lubrica-
tion is not necessary.
OPERATION
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
radiator core, cooling system hoses and heater core,
this coolant absorbs the heat generated when the
engine is running. The pump is driven by the engine
crankshaft via a drive belt.
DIAGNOSIS AND TESTINGÐWATER PUMP
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.
Fig. 38 Pressure Testing Radiator Cap - Typical
1 - PRESSURE CAP
2 - TYPICAL COOLING SYSTEM PRESSURE TESTER
Fig. 39 Radiator Pressure Cap
1 - STAINLESS-STEEL SWIVEL TOP
2 - RUBBER SEALS
3 - VENT VALVE
4 - RADIATOR TANK
5 - FILLER NECK
6 - OVERFLOW NIPPLE
7 - MAIN SPRING
8 - GASKET RETAINER
7 - 62 ENGINEDR
RADIATOR PRESSURE CAP (Continued)