2003 DODGE RAM cooling

CONDITION POSSIBLE CAUSES CORRECTION
TEMPERATURE GAUGE
READS HIGH OR THE
COOLANT WARNING LAMP
ILLUMINATES. COOLANT MAY
OR MAY NOT BE LOST OR
LEAKING FROM THE COOLING
SYSTEM1. Trailer is being towed, a steep
hill is being climbed, vehicle is
operated in slow moving traffic,
or engine is being idled with
very high ambient (outside)
temperatures and the air
conditioning is on. Higher
altitudes could aggravate these
conditions.1. This may be a temporary condition and
repair is not necessary. Turn off the air
conditioning and attempt to drive the
vehicle without any of the previous
conditions. Observe the temperature
gauge. The gauge should return to the
normal range. If the gauge does not return
to the normal range, determine the cause
for overheating and repair. Refer to
Possible Causes (2-18).
2. Is the temperature gauge
reading correctly?2. Check gauge. (Refer to 8 -
ELECTRICAL/INSTRUMENT CLUSTER -
SCHEMATIC - ELECTRICAL). Repair as
necessary.
3. Is the temperature warning
illuminating unnecessarily?3. (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER - SCHEMATIC -
ELECTRICAL).
4. Coolant low in coolant
reserve/overflow tank and
radiator?4. Check for coolant leaks and repair as
necessary. (Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).
5. Pressure cap not installed
tightly. If cap is loose, boiling
point of coolant will be lowered.
Also refer to the following Step
6.5. Tighten cap
6. Poor seals at the radiator
cap.6. (a) Check condition of cap and cap
seals. Refer to Radiator Cap. Replace cap
if necessary.
(b) Check condition of radiator filler neck.
If neck is bent or damaged, replace
radiator (5.9L) or degas bottle (3.7L, 4.7L).
7. Coolant level low in radiator
but not in coolant reserve/
overflow tank. This means the
radiator is not drawing coolant
from the coolant reserve/
overflow tank as the engine
cools (5.9L).7. (a) Check condition of radiator cap and
cap seals. Refer to Radiator Cap in this
Group. Replace cap if necessary.
(b) Check condition of radiator filler neck.
If neck is bent or damaged, replace
radiator.
(c) Check condition of the hose from the
radiator to the coolant tank. It should fit
tight at both ends without any kinks or
tears. Replace hose if necessary.
(d) Check coolant reserve/overflow tank
and tanks hoses for blockage. Repair as
necessary.
8. Incorrect coolant
concentration8. Check coolant. (Refer to LUBRICATION
& MAINTENANCE/FLUID TYPES -
DESCRIPTION).
9. Coolant not flowing through
system9. Check for coolant flow at radiator filler
neck with some coolant removed, engine
warm and thermostat open. Coolant
should be observed flowing through
radiator. If flow is not observed, determine
area of obstruction and repair as
necessary.
7 - 12 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
Temperature gauge reading is
inconsistent (flucttuates, cycles
or is erratic)1. During cold weather
operation, with the heater blower
in the high position, the gauge
reading may drop slightly.1. A normal condition. No correction
necessary.
2. Temperature gauge or engine
mounted gauge sensor defective
or shorted. Also, corroded or
loose wiring in this circuit.2. Check operation of gauge and repair if
necessary. (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER - DIAGNOSIS
AND TESTING).
3. Gauge reading rises when
vehicle is brought to a stop after
heavy use (engine still running)3. A normal condition. No correction is
necessary. Gauge should return to normal
range after vehicle is driven.
4. Gauge reading high after
re-starting a warmed up (hot)
engine.4. A normal condition. No correction is
necessary. The gauge should return to
normal range after a few minutes of
engine operation.
5. Coolant level low in radiator
(air will build up in the cooling
system causing the thermostat
to open late).5. Check and correct coolant leaks. (Refer
to 7 - COOLING - DIAGNOSIS AND
TESTING).
6. Cylinder head gasket leaking
allowing exhaust gas to enter
cooling system causing a
thermostat to open late.6. (a) Check for cylinder head gasket
leaks. (Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).
(b) Check for coolant in the engine oil.
Inspect for white steam emitting from the
exhaust system. Repair as necessary.
7. Water pump impeller loose on
shaft.7. Check water pump and replace as
necessary. (Refer to 7 - COOLING/
ENGINE/WATER PUMP - REMOVAL).
8. Loose accessory drive belt.
(water pump slipping)8. (Refer to 7 - COOLING/ACCESSORY
DRIVE/DRIVE BELTS - DIAGNOSIS AND
TESTING). Check and correct as
necessary.
9. Air leak on the suction side of
the water pump allows air to
build up in cooling system
causing thermostat to open late.9. Locate leak and repair as necessary.
PRESSURE CAP IS BLOWING
OFF STEAM AND/OR
COOLANT TO COOLANT TANK.
TEMPERATURE GAUGE
READING MAY BE ABOVE
NORMAL BUT NOT HIGH.
COOLANT LEVEL MAY BE
HIGH IN COOLANT RESERVE/
OVERFLOW TANK1. Pressure relief valve in
radiator cap is defective.1. Check condition of radiator cap and cap
seals. (Refer to 7 - COOLING/ENGINE/
RADIATOR PRESSURE CAP -
DIAGNOSIS AND TESTING). Replace cap
as necessary.
COOLANT LOSS TO THE
GROUND WITHOUT
PRESSURE CAP BLOWOFF.
GAUGE READING HIGH OR
HOT1. Coolant leaks in radiator,
cooling system hoses, water
pump or engine.1. Pressure test and repair as necessary.
(Refer to 7 - COOLING - DIAGNOSIS
AND TESTING).
7 - 14 COOLINGDR
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
DETONATION OR PRE-
IGNITION (NOT CAUSED BY
IGNITION SYSTEM). GAUGE
MAY OR MAY NOT BE
READING HIGH1. Engine overheating. 1. Check reason for overheating and
repair as necessary.
2. Freeze point of coolant not
correct. Mixture is too rich or too
lean.2. Check coolant concentration. (Refer to
LUBRICATION & MAINTENANCE/FLUID
TYPES - DESCRIPTION).
HOSE OR HOSES COLLAPSE
WHILE ENGINE IS RUNNING1. Vacuum created in cooling
system on engine cool-down is
not being relieved through
coolant reserve/overflow system.1. (a) Radiator cap relief valve stuck.
(Refer to 7 - COOLING/ENGINE/
RADIATOR PRESSURE CAP -
DIAGNOSIS AND TESTING). Replace if
necessary
(b) Hose between coolant
reserve/overflow tank and
radiator is kinked. Repair as
necessary.
(c) Vent at coolant reserve/
overflow tank is plugged. Clean
vent and repair as necessary.
(d) Reserve/overflow tank is internally
blocked or plugged. Check for blockage
and repair as necessary.
NOISY VISCOUS FAN/DRIVE 1. Fan blades loose. 1. Replace fan blade assembly. (Refer to 7
- COOLING/ENGINE/RADIATOR FAN -
REMOVAL)
2. Fan blades striking a
surrounding object.2. Locate point of fan blade contact and
repair as necessary.
3. Air obstructions at radiator or
air conditioning condenser.3. Remove obstructions and/or clean
debris or insects from radiator or A/C
condenser.
4. Thermal viscous fan drive has
defective bearing.4. Replace fan drive. Bearing is not
serviceable. (Refer to 7 - COOLING/
ENGINE/FAN DRIVE VISCOUS CLUTCH
- REMOVAL).
5. A certain amount of fan noise
may be evident on models
equipped with a thermal viscous
fan drive. Some of this noise is
normal.5. (Refer to 7 - COOLING/ENGINE/FAN
DRIVE VISCOUS CLUTCH -
DESCRIPTION) for an explanation of
normal fan noise.
DRCOOLING 7 - 15
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)

CAUTION: Follow manufacturers instructions when
using these products.
STANDARD PROCEDUREÐDRAINING COOLING
SYSTEM 3.7L/4.7L/5.7L ENGINE
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS (Fig. 6) OR LOOSEN THE
RADIATOR DRAINCOCK WITH SYSTEM HOT AND
UNDER PRESSURE. SERIOUS BURNS FROM
COOLANT CAN OCCUR.
(1) With the engine cold, raise the vehicle on a
hoist and locate the radiator draincock.
NOTE: Radiator draincock is located on the left/
lower side of radiator facing to rear of vehicle.
(2) Attach one end of a hose to the draincock. Put
the other end into a clean container. Remove the
radiator cap, open the draincock and drain the cool-
ing system.
(3) If draining the entire engine is required,
remove the cylinder block drain plugs.
STANDARD PROCEDURE - REFILLING
COOLING SYSTEM 3.7L/4.7L/5.7L ENGINE
DO NOT WASTE REUSABLE COOLANT.Ifthe
solution is clean, drain the coolant into a clean con-
tainer for reuse.(1) Install the cylinder block drain plugs (if
removed). Coat the threads with MopartThread
Sealant with Teflon.
(2) Close the radiator draincock.
CAUTION: Failure to purge air from the cooling sys-
tem can result in an overheating condition and
severe engine damage.
(3) Fill system using a 50/50 mixture antifreeze
and low mineral content water. Stop filling when the
level in the degas bottle has reached the top of the
COLD FILL RANGE.
(4) Start and operate the engine until the thermo-
stat opens (upper radiator hose is warm to the
touch).
(5) If necessary, add a 50/50 mixture of anti-freeze
and water to the degass bottle to maintain the proper
coolant level in the degas bottle.
(6) Install the radiator cap.
STANDARD PROCEDUREÐDRAINING COOLING
SYSTEM 5.9L/8.0L ENGINE
WARNING: DO NOT REMOVE CYLINDER BLOCK
DRAIN PLUGS OR LOOSEN RADIATOR DRAIN-
COCK WITH SYSTEM HOT AND UNDER PRESSURE.
SERIOUS BURNS FROM COOLANT CAN OCCUR.
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
(1) Attach one end of a hose to the draincock. Put
the other end into a clean container.
(2)DO NOT REMOVE THE RADIATOR CAP
when draining the coolant from the reservoir/over-
flow tank. Open radiator draincock and when the
tank is empty, remove the radiator cap and continue
draining the cooling system.
(3) If draining the entire engine, remove the cylin-
der block drain plugs. Refer to (Fig. 7).
STANDARD PROCEDUREÐREFILLING
COOLING SYSTEM 5.9L/8.0L ENGINE
WARNING: DO NOT REMOVE CYLINDER BLOCK
DRAIN PLUGS OR LOOSEN RADIATOR DRAIN-
COCK WITH SYSTEM HOT AND UNDER PRESSURE.
SERIOUS BURNS FROM COOLANT CAN OCCUR.
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
Clean cooling system prior to refilling. (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(1) Install cylinder block drain plugs. Coat the
threads with MopartThread Sealant with Teflon.
(2) Close radiator petcock.
Fig. 6 Drain Plug - 3.7L/4.7L Engine
1 - CYLINDER BLOCK DRAIN PLUG
2 - EXHAUST MANIFOLD AND HEAT SHIELD
7 - 18 COOLINGDR
COOLING (Continued)

(3) Fill cooling system with a 50/50 mixture of
water and antifreeze.
(4) Fill coolant reserve/overflow tank to MAX mark
on bottle.
(5) Start and operate engine until thermostat
opens (upper radiator hose warm to touch).
(6) If necessary, add a 50/50 water and antifreeze
mixture to the coolant reserve/overflow tank. This is
done to maintain coolant level between the MAX and
MIN marks. The level in the reserve/overflow tank
may drop below the MIN mark after three or four
warm-up and cool-down cycles.
STANDARD PROCEDUREÐDRAINING COOLING
SYSTEM 5.9L DIESEL ENGINE
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.
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.
(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,
(Refer to 7 - COOLING - DIAGNOSIS AND TEST-
ING). The coolant need not be removed from tank
unless the system is being refilled with fresh mix-
ture.
(4) Remove radiator pressure cap.
STANDARD PROCEDUREÐREFILLING
COOLING SYSTEM 5.9L DIESEL ENGINE
Clean cooling system prior to refilling (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(1) Close radiator drain plug.
CAUTION: Due to the use of the one-way check
valve, the engine must not be operating when refill-
ing the cooling system.
NOTE: The diesel engine is equipped with two one-
way check valves (jiggle pins). The check valves
are used as a servicing feature and will vent air
when the system is being filled. Water pressure (or
flow) will hold the valves closed.
(2) Fill the cooling system with a 50/50 mixture of
water and antifreeze.
(3) Fill coolant reserve/overflow tank to the FULL
mark.
(4) Start and operate engine until thermostat
opens. Upper radiator hose should be warm to touch.
(5) 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
ADD and FULL marks. The level in the reserve/over-
flow tank may drop below the ADD mark after three
or four warm-up and cool-down cycles.
STANDARD PROCEDURE - ADDING
ADDITIONAL COOLANT
The use of aluminum cylinder blocks, cylinder
heads and water pumps requires special corrosion
protection. Only MopartAntifreeze/Coolant, 5
Year/100,000 Mile Formula (glycol base coolant with
corrosion inhibitors called HOAT, for Hybrid Organic
Additive Technology) is recommended. This coolant
offers the best engine cooling without corrosion when
mixed with 50% distilled water to obtain a freeze
point of -37ÉC (-35ÉF). If it loses color or becomes con-
taminated, drain, flush, and replace with fresh prop-
erly mixed coolant solution.
CAUTION: Do not use coolant additives that are
claimed to improve engine cooling.
For 5.9L engines, do not remove the radiator cap to
add coolant to the system. When adding coolant to
maintain the correct level, do so only at the reserve/
overflow bottle. Remove the radiator cap only for
testing or when refilling the system after service.
Removing the cap unnecessarily can cause loss of
coolant and allow air to enter the system, which pro-
duces corrosion.
Fig. 7 Cylinder Block Drain Plug - 5.9L Engines
1 - BLOCK DRAIN PLUG
DRCOOLING 7 - 19
COOLING (Continued)