2003 DODGE RAM cooling system flow

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)

water pump while removing pump from vehicle. Do
not remove the clamp from the bypass hose.
(9) Discard the old gasket.
CAUTION: Do not pry the water pump at timing
chain case/cover. The machined surfaces may be
damaged resulting in leaks.
CLEANING
Clean gasket mating surfaces as necessary.
INSPECTION
Visually inspect the water pump and replace if it
has any of the following conditions:
²The body is cracked or damaged
²Water leaks from the shaft seal. This is evident
by traces of coolant below the vent hole
²Loose or rough turning bearing.
²Impeller rubbing the pump body
INSTALLATION
(1) Clean the gasket mating surfaces.
(2) Using a new gasket, install the water pump to
the engine as follows: Guide the water pump tube
into the bypass hose as the pump is being installed.
Install the water pump bolts (Fig. 43). Tighten the
water pump mounting bolts to 40 N´m (30 ft. lbs.)
torque.
(3) Position the bypass hose clamp to the bypass
hose.
(4) Spin the water pump to be sure that the pump
impeller does not rub against the timing chain case/
cover.
(5) Install a new o-ring to the heater hose coolant
return tube (Fig. 42). Coat the new o-ring with anti-
freeze before installation.(6) Install the coolant return tube and its mount-
ing bolt to the engine (Fig. 42). Be sure the slot in
the tube bracket is bottomed to mounting bolt. This
will properly position return tube.
(7) Connect the radiator lower hose to the water
pump.
(8) Connect the heater hose and hose clamp to the
coolant return tube.
(9) Install drive belt (Refer to 7 - COOLING/AC-
CESSORY DRIVE/DRIVE BELTS - INSTALLATION)
(Fig. 41).
(10) Install the fan (Refer to 7 - COOLING/EN-
GINE/RADIATOR FAN - INSTALLATION)
(11) Fill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(12) Connect negative battery cable.
(13) Start and warm the engine. Check for leaks.
WATER PUMP - 3.7L/4.7L
DESCRIPTION
DESCRIPTIONÐWATER PUMP
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
single serpentine drive belt.
The water pump impeller is pressed onto the rear
of a shaft that rotates in bearings pressed into the
housing. The housing has two small holes to allow
seepage to escape. The water pump seals are lubri-
cated by the antifreeze in the coolant mixture. No
additional lubrication is necessary.
Both heater hoses are connected to fittings on the
timing chain front cover. The water pump is also
mounted directly to the timing chain cover and is
equipped with a non serviceable integral pulley (Fig.
44).
DESCRIPTIONÐWATER PUMP BYPASS
The 3.7L and 4.7L engine uses an internal water/
coolant bypass system. The design uses galleries in
the timing chain cover to circulate coolant during
engine warm-up preventing the coolant from flowing
through the radiator. The thermostat uses a stub
shaft located at the rear of the thermostat (Fig. 45)
to control flow through the bypass gallery.
OPERATION
OPERATIONÐWATER PUMP
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
Fig. 43 Water Pump Bolts - 5.9L V-8 Gas Engine -
Typical
1 - WATER PUMP MOUNTING BOLTS
7 - 64 ENGINEDR
WATER PUMP - 5.9L (Continued)

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.
OPERATIONÐWATER PUMP BYPASS
When the thermostat is in the closed position the
bypass gallery is not obstructed allowing 100% flow.
When the thermostat is in the open position the stub
shaft enters the bypass gallery obstructing bypass
coolant flow by 50%. This design allows the coolant
to reach operating temperature quickly when cold,
while adding extra cooling during normal tempera-
ture operation.
REMOVAL
The water pump on 3.7L/4.7L engines is bolted
directly to the engine timing chain case cover.
(1) Disconnect the negative battery cable.
(2) Drain cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(3) Remove fan/viscous fan drive assembly from
water pump (Fig. 46) (Refer to 7 - COOLING/EN-
GINE/FAN DRIVE VISCOUS CLUTCH - REMOV-
AL). Do not attempt to remove fan/viscous fan drive
assembly from vehicle at this time.
WARNING: CONSTANT TENSION HOSE CLAMPS
ARE USED ON MOST COOLING SYSTEM HOSES.WHEN REMOVING OR INSTALLING, USE ONLY
TOOLS DESIGNED FOR SERVICING THIS TYPE OF
CLAMP. ALWAYS WEAR SAFETY GLASSES WHEN
SERVICING CONSTANT TENSION CLAMPS.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only an original equipment clamp
with matching number or letter and width.
(4) If the water pump is being replaced, do not
unbolt the fan blade assembly from the thermal vis-
cous fan drive.
(5) Remove the radiator fan (Refer to 7 - COOL-
ING/ENGINE/RADIATOR FAN - REMOVAL).
(6) Remove accessory drive belt (Fig. 47) (Refer to
7 - COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(7) Remove the lower radiator hose clamp and
remove the lower hose at the water pump.
(8) Remove the water pump mounting bolts.
Fig. 44 Water Pump and Timing Chain Cover
1 - INTEGRAL WATER PUMP PULLEY
2 - TIMING CHAIN COVER
3 - THERMOSTAT HOUSING
4 - HEATER HOSE FITTINGS
5 - WATER PUMP
Fig. 45 Water/Coolant Bypass Flow and Thermostat
1 - FROM HEATER AND DEGAS CONTAINER
2 - FROM RADIATOR
3 - TO WATER PUMP
4 - ENGINE BYPASS
5 - THERMOSTAT
DRENGINE 7 - 65
WATER PUMP - 3.7L/4.7L (Continued)

ers are supplied as standard equipment on diesel
engine powered models when equipped with an auto-
matic transmission.
The main water-to-oil transmission oil cooler is
mounted to a bracket on the intake side of the engine
(Fig. 4).
The air-to-oil cooler is located in front of and to the
left side of the radiator (Fig. 5).
OPERATION
The transmission oil is routed through the main
cooler first, then the auxiliary cooler where addi-
tional heat is removed from the transmission oil
before returning to the transmission. The cooler has
an internal thermostat that controls fluid flow
through the cooler. When the transmission fluid is
cold (less then operating temperature), the fluid is
routed through the cooler bypass. When the trans-
mission fluid reaches operating temperatures and
above, the thermostat closes off the bypass allowing
fluid flow through the cooler. The thermostat is ser-
vicable.
REMOVAL
REMOVALÐAIR TO OIL COOLER
(1) Remove Charge Air Cooler (Refer to 11 -
EXHAUST SYSTEM/TURBOCHARGER SYSTEM/
CHARGE AIR COOLER AND PLUMBING -
REMOVAL).(2) Place a drain pan under the oil cooler.
(3) Raise the vehicle.
(4) Disconnect the oil cooler quick-connect fittings
from the transmission lines.
(5) Remove the charge air cooler-to-oil cooler bolt
(Fig. 6).
(6) Remove two mounting nuts.
(7) Remove the oil cooler and line assembly
towards the front of vehicle. Cooler must be rotated
and tilted into position while removing.
REMOVALÐWATER TO OIL COOLER
CAUTION: If a leak should occur in the water-to-oil
cooler mounted to the side of the engine block,
engine coolant may become mixed with transmis-
sion fluid. Transmission fluid may also enter engine
cooling system. Both cooling system and transmis-
sion should be drained and inspected in case of oil
cooler leakage.
(1) Disconnect both battery negative cables.
(2) Remove starter (Refer to 8 - ELECTRICAL/
STARTING/STARTER MOTOR - REMOVAL).
(3) Drain cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(4) Disconnect coolant lines from cooler.
Fig. 4 Transmission Water-To-Oil CoolerÐDiesel
EngineÐTypical
1 - TRANSMISSION WATER-TO-OIL COOLER
Fig. 5 Auxiliary Transmission Oil CoolerÐDiesel
Engine
1 - MOUNTING BOLTS
2 - RADIATOR
3 - QUICK-CONNECT FITTINGS
4 - TRANSMISSION OIL COOLER
7 - 74 TRANSMISSIONDR
TRANS COOLER - 5.9L DIESEL (Continued)

(9) Position and install heater hoses and tubes
onto intake manifold.
(10) Install the heater hoses to the heater core and
engine front cover.
(11) Connect electrical connectors for the following
components:
²Manifold Absolute Pressure (MAP) Sensor
²Intake Air Temperature (IAT) Sensor
²Throttle Position (TPS) Sensor
²Coolant Temperature (CTS) Sensor
²Idle Air Control (IAC) Motor
²Ignition coil towers
²Fuel injectors
(12) Install top oil dipstick tube retaining bolt and
ground strap.
(13) Connect generator electrical connections.
(14) Connect Vapor purge hose, Brake booster
hose, Speed control servo hose, Positive crankcase
ventilation (PCV) hose.
(15) Fill cooling system.
(16) Install resonator assembly and air inlet hose.
(17) Connect negative cable to battery.
EXHAUST MANIFOLD
DESCRIPTION
The exhaust manifolds (Fig. 91) are log style with
a patented flow enhancing design to maximize perfor-
mance. The exhaust manifolds are made of high sili-
con molybdenum cast iron. A perforated core graphiteexhaust manifold gasket is used to improve sealing
to the cylinder head. The exhaust manifolds are cov-
ered by a three layer laminated heat shield for ther-
mal protection and noise reduction. The heat shields
(Fig. 92) are fastened with a torque prevailing nut
that is backed off slightly to allow for the thermal
expansion of the exhaust manifold.
REMOVAL
RIGHT EXHAUST MANIFOLD
(1) Disconnect the negative cable from the battery.
(2) Raise and support the vehicle.
(3) Remove the bolts and nuts attaching the
exhaust pipe to the engine exhaust manifold.
(4) Lower the vehicle.
(5) Remove the exhaust heat shield (Fig. 93).
(6) Remove bolts, nuts and washers attaching
manifold to cylinder head.
(7) Remove manifold and gasket from the cylinder
head.
Fig. 91 EXHAUST MANIFOLDS
1 - LEFT SIDE EXHAUST MANIFOLD
2 - RIGHT SIDE EXHAUST MANIFOLD
Fig. 92 Exhaust Manifold Heat Shields
1 - RIGHT SIDE EXHAUST MANIFOLD HEAT SHIELD
2 - RIGHT SIDE EXHAUST MANIFOLD FLANGE
3 - LEFT SIDE EXHAUST MANIFOLD HEAT SHIELD
4 - LEFT SIDE EXHAUST MANIFOLD FLANGE
DRENGINE - 3.7L 9 - 73
INTAKE MANIFOLD (Continued)

SPECIFICATIONS
5.7L ENGINE
DESCRIPTION SPECIFICATION
GENERAL SPECIFICATIONS
Engine Type 90É V-8 OHV
Bore and Stroke 99.5 x 90.9 mm
(3.91 x 3.58 in.)
Displacement 5.7L (345 c.i.)
Compression Ratio 9.6:1
Firing Order 1±8±4±3±6±5±7±2
Lubrication Pressure Feed ± Full
Flow
Filtration
Cooling System Liquid Cooled ± Forced
Circulation
Cylinder Block Cast Iron
Cylinder Head Aluminum
Crankshaft Nodular Iron
Camshaft Hollow assembled
camshaft
Pistons Aluminum Alloy w/strut
Connecting Rods Powdered metal
CAMSHAFT
Bearing Journal Diameter
No. 1 58.2 mm
(2.29 in.)
No. 2 57.8 mm
(2.27 in.)
No. 3 57.4 mm
(2.26 in.)
No. 4 57.0 mm
(2.24 in.)
No. 5 43.633 mm
(1.72 in.)
DESCRIPTION SPECIFICATION
Bearing to Journal
Clearance Standard
No. 1 0.040 ± 0.080 mm
(.0015 ± .003 in.)
No. 2 0.050 ± 0.090 mm
(0.0019 ± .0035 in.)
No. 3 0.040 ± 0.080 mm
(.0015 ± .003 in.)
No. 4 0.050 ± 0.090 mm
(0.0019 ± .0035 in.)
No. 5 0.040 ± 0.080 mm
(.0015 ± .003 in.)
Camshaft End Play 0.080 - 0.290 mm
(0.0031 - 0.0114 in.)
CONNECTING RODS
Piston Pin bore Diameter 23.955 ± 23.975 mm
(0.9431 ± 0.9438 in.)
Side Clearance 0.10 - 0.35mm
( 0.003 - 0.0137 in.)
CRANKSHAFT
Rod Journal
Diameter 53.992 ± 54.008 mm
(2.125 ± 2.126 in.)
Out of Round (Max.) 0.005 mm (0.0002 in.)
Taper (Max.) 0.003 mm ( 0.0001 in.)
Bearing Clearance 0.020 ± 0.060 mm
(0.0007 ± 0.0023 in.)
Main Bearing Journal
Diameter 64.988 ± 65.012 mm
(2.5585 ± 2.5595 in.)
Out of Round (Max.) 0.005 mm (0.0002 in.)
Taper (Max.) 0.003 mm (0.0001 in.)
Bearing Clearance
0.023 ± 0.051mm
(0.0009 ± 0.002 in.)
Crankshaft End Play 0.052 ± 0.282 mm
(0.002 ± 0.011 in.)
Service Limit 0.282 mm ( 0.011 in.)
9 - 188 ENGINE - 5.7LDR
ENGINE - 5.7L (Continued)

the outside in a crisscross pattern. Torque fasteners
to 12 N´m (105 in. lbs.).
(4) Connect electrical connectors for the following
components:
²Manifold Absolute Pressure (MAP) Sensor
²Intake Air Temperature (IAT) Sensor
²Throttle Position (TPS) Sensor
²Coolant Temperature (CTS) Sensor
²Idle Air Control (IAC) Motor
(5) Install generator.
(6) Install A/C compressor.
(7) Connect Brake booster hose and Positive crank-
case ventilation (PCV) hose.
(8) Install resonator assembly and air inlet hose.
(9) Connect negative cable to battery.
EXHAUST MANIFOLD
DESCRIPTION
The exhaust manifolds are log style with a pat-
ented flow enhancing design to maximize perfor-
mance. The exhaust manifolds are made of high
silicon molybdenum cast iron. A perforated core
graphite exhaust manifold gasket is used to improve
sealing to the cylinder head. The exhaust manifolds
are covered by a three layer laminated heat shield
for thermal protection and noise reduction. The heat
shields are fastened with a torque prevailing nut
that is backed off slightly to allow for the thermal
expansion of the exhaust manifold.
OPERATION
The exhaust manifolds collect the engine exhaust
exiting the combustion chambers, then channels the
exhaust gases to the exhaust pipes attached to the
manifolds.
REMOVAL
EXHAUST MANIFOLD
(1) Disconnect negative battery cable.
(2) Raise vehicle.
(3) Remove exhaust pipe to manifold bolts.
(4) Lower vehicle.
(5) Install engine support fixture special tool
#8534.
(6) Raise engine enough to remove manifolds.
CAUTION: Do not damage engine harness while
raising the engine.
(7) Remove heat shield.
(8) Remove manifold bolts.
(9) Remove manifold and gasket.
CLEANING
Clean mating surfaces on cylinder head and mani-
fold. Wash with solvent and blow dry with com-
pressed air.
INSPECTION
Inspect manifold for cracks.
Inspect mating surfaces of manifold for flatness
with a straight edge. Gasket surfaces must be flat
within 0.2 mm per 300 mm (0.008 inch per foot).
INSTALLATION
EXHAUST MANIFOLD
(1) Install manifold gasket and manifold.
(2) Install manifold bolts and tighten to 25 N´m
(18 ft. lbs.).
(3) Install heat shield and tighten nuts to 15 N´m
(11 ft. lbs.).
(4) Lower engine.
CAUTION: Do not damage engine harness while
lowering the engine.
(5) Remove engine support fixture from engine.
(6) Raise vehicle.
(7) Tighten right and left side engine mount
through bolts.
(8) Install exhaust flange to pipe bolts.
(9) Lower vehicle.
(10) Connect negative battery cable.
TIMING/CHAIN COVER
REMOVAL
(1) Disconnect the battery negative cable.
(2) Remove air cleaner assembly.
(3) Drain cooling system.
(4) Remove accessory drive belt.
(5) Remove fan and fan drive assembly (Refer to 7
- COOLING/ENGINE/FAN DRIVE VISCOUS
CLUTCH - REMOVAL).
(6) Remove coolant bottle and washer bottle.
(7) Remove fan shroud.
NOTE: It is not necessary to disconnect A/C lines or
discharge freon.
(8) Remove A/C compressor and set aside.
(9) Remove the generator.
(10) Remove upper radiator hose.
(11) Disconnect both heater hoses at timing cover.
(12) Disconnect lower radiator hose at engine.
(13) Remove accessory drive belt tensioner and
both idler pulleys.
9 - 220 ENGINE - 5.7LDR
INTAKE MANIFOLD (Continued)

(19) Install the distributor cap and wiring.
(20) Install the intake manifold (Refer to 9 -
ENGINE/MANIFOLDS/INTAKE MANIFOLD -
INSTALLATION).
(21) Using a new gasket, install throttle body
(Refer to 14 - FUEL SYSTEM/FUEL INJECTION/
THROTTLE BODY - INSTALLATION).
(22) Connect the throttle linkage (Refer to 14 -
FUEL SYSTEM/FUEL INJECTION/THROTTLE
CONTROL CABLE - INSTALLATION).
(23) Install the air cleaner resonator and duct
work..
(24) Install the generator and wire connections
(Refer to 8 - ELECTRICAL/CHARGING/GENERA-
TOR - INSTALLATION).
(25) Install a/c compressor and lines (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/A/C
COMPRESSOR - INSTALLATION).
(26) Install the accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION).
(27) Install upper radiator support crossmember.
(28) Install radiator (Refer to 7 - COOLING/EN-
GINE/RADIATOR - INSTALLATION).
(29) Connect the radiator lower hose.
(30) Connect the transmission oil cooler lines to
the radiator.
(31) Install the fan shroud.
(32) Install the fan (Refer to 7 - COOLING/EN-
GINE/RADIATOR FAN - INSTALLATION).
(33) Connect the radiator upper hose.
(34) Install the washer bottle.
(35) Install the transmission oil cooler (Refer to 7 -
COOLING/TRANSMISSION/TRANS COOLER -
INSTALLATION).
(36) Connect the transmission cooler lines.
(37) If equipped, install the condenser (Refer to 24
- HEATING & AIR CONDITIONING/PLUMBING/
A/C CONDENSER - INSTALLATION).
(38) Evacuate and charge the air conditioning sys-
tem, if equipped (Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING - STANDARD PRO-
CEDURE).
(39) Add engine oil to crankcase (Refer to LUBRI-
CATION & MAINTENANCE/FLUID TYPES - SPEC-
IFICATIONS).
(40) Fill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(41) Connect battery negative cable.
(42) Start engine and inspect for leaks.
(43) Road test vehicle.SPECIFICATIONS
5.9L ENGINE
ENGINE SPECIFICATIONS
DESCRIPTION SPECIFICATION
GENERAL SPECIFICATIONS
Engine Type 90É V-8 OHV
Bore and Stroke 101.6 x 90.9 mm
(4.00 x 3.58 in.)
Displacement 5.9L (360 c.i.)
Compression Ratio 9.1:1
Firing Order 1±8±4±3±6±5±7±2
Lubrication Pressure Feed ± Full
Flow
Filtration
Cooling System Liquid Cooled ± Forced
Circulation
Cylinder Block Cast Iron
Cylinder Head Cast Iron
Crankshaft Nodular Iron
Camshaft Nodular Cast Iron
Pistons Aluminum Alloy w/strut
Connecting Rods Forged Steel
Compression Pressure 689.5 kPa (100 psi)
(Min.)
CAMSHAFT
Bearing Diameter
No. 1 50.800 ± 50.825 mm
(2.000 ± 2.001 in.)
No. 2 50.394 ± 50.419 mm
(1.984 ± 1.985 in.)
No. 3 50.013 ± 50.038 mm
(1.969 ± 1.970 in.)
No. 4 49.606 ± 49.632 mm
(1.953 ± 1.954 in.)
No. 5 39.688 ± 39.713 mm
(1.5625 ± 1.5635 in.)
DRENGINE - 5.9L 9 - 235
ENGINE - 5.9L (Continued)