2003 JEEP GRAND CHEROKEE Hoses

HEATER CORE
DESCRIPTION
The heater core is located in the HVAC housing,
under the instrument panel. It is a heat exchanger
made of rows of tubes and fins.
OPERATION
Engine coolant is circulated through heater hoses
to the heater core at all times. As the coolant flows
through the heater core, heat removed from the
engine is transferred to the heater core fins and
tubes. Air directed through the heater core picks up
the heat from the heater core fins. The temperature
control door allows control of the heater output air
temperature by controlling how much of the air flow-
ing through the HVAC housing is directed through
the heater core. The blower motor speed controls the
volume of air flowing through the HVAC housing.
The heater core cannot be repaired and, if faulty or
damaged, it must be replaced. Refer to Cooling for
more information on the engine cooling system, the
engine coolant and the heater hoses.
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)
(1) Remove the HVAC housing from the vehicle.
(Refer to 24 - HEATING & AIR CONDITIONING/
DISTRIBUTION/HVAC HOUSING - REMOVAL)
(2) Remove the foam gasket surrounding the core
tubes.
NOTE: Notice the orientation of the irregularly
shaped gasket on the tubes. The gasket must be
placed correctly to ensure proper sealing against
the body during reinstallation.(3)
Remove the screws and retainers that secure the
heater core and tubes to the HVAC housing (Fig. 12).
(4) Remove the mode door actuator if necessary,
for clearance to remove the core.
(5) Lift the heater core straight up and out of the
HVAC housing (Fig. 13).
(6) When replacing individual tubes, loosen and
remove the round tube-to-core clamp, and pull tube
from core.
INSTALLATION
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)
Any kinks or sharp bends in the refrigerant plumb-
ing will reduce the capacity of the entire air condi-
tioning system. Kinks and sharp bends reduce the
flow of refrigerant in the system. A good rule for the
flexible hose refrigerant lines is to keep the radius of
all bends at least ten times the diameter of the hose.
In addition, the flexible hose refrigerant lines should
be routed so they are at least 80 millimeters (3
inches) from the exhaust manifold.
High pressures are produced in the refrigerant sys-
tem when the air conditioning compressor is operat-
ing. Extreme care must be exercised to make sure
that each of the refrigerant system connections is
Fig. 12 HEATER CORE, TUBES, AND RETAINERS
1 - TUBE-TO-CORE CLAMPS
2 - GROUND STRAP
3 - HVAC HOUSING
4 - TUBE RETAINERS AND SCREWS
5 - HEATER CORE
WJPLUMBING 24 - 71

VISCOUS HEATER
DESCRIPTION
DESCRIPTION
The diesel engine has an engine mounted mechan-
ical device called a Viscous Heater that is used to
heat the coolant coming from the engine to the
heater core. The Viscous Heater is driven by the
engine fan belt and has a electro-mechanical clutch
which is controlled by the HVAC control unit.
DESCRIPTION - VISCOUS HEATER CLUTCH
The basic viscous heater clutch assembly consists
of a stationary electromagnetic coil, a hub bearing
and pulley assembly and a clutch plate. The electro-
magnetic coil unit and the hub bearing and pulley
assembly are each retained on the nose of the com-
pressor front housing with snap rings (Fig. 17). The
clutch plate is keyed to the viscous heater shaft and
secured with a nut. These components provide the
means to engage and disengage the viscous heater
from the engine accessory drive belt.
OPERATION
OPERATION - VISCOUS HEATER
The Viscous Heater is driven by the engine fan
belt. The Viscous Heater has an electro-mechanical
clutch that receives a signal from the HVAC control
head and the Viscous Heater controller that ener-
gizes and engages the clutch. Once engaged theclutch allows the Viscous Heater to increase the tem-
perature of the coolant flowing to the heater core,
which provides heat the passenger compartment
quicker than normal engines without the Viscous
Heater. The Viscous Heater generates heat by means
of friction which heats a special Silicon Oil within its
housing which is then transferred to the engine cool-
ant when the coolant passes over fins within the
pump. Please note that the coolant is isolated from
the silicon oil within the pump housing. When
demand for passenger compartment heat decreases
the Viscous Heater clutch will receive an input from
the Viscous heater controller to disengage.
OPERATION - VISCOUS HEATER CLUTCH
When the clutch coil is energized, it magnetically
draws the clutch into contact with the pulley and
drives the viscous heater shaft. When the coil is not
energized the pulley freewheels on the clutch hub
bearing, which is part of the pulley. The viscous
heater clutch and coil are the only serviced parts on
the viscous heater assembly. If the viscous heater is
inoperative or damaged the entire assembly must be
replaced. The viscous heater clutch engagement is
controlled by several components: the viscous heater
controller, the engine powertrain control module and
the HVAC control head.
REMOVAL
REMOVAL - VISCOUS HEATER
(1) Drain the engine coolant(Refer to 7 - COOL-
ING/ENGINE - STANDARD PROCEDURE).
(2) Remove the engine accessory drive belt(Refer to
7 - COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(3) Remove the heater hose clamps at the Viscous
Heater.
(4) Remove the heater hoses from the Viscous
Heater.
(5) Unplug the Viscous Heater clutch electrical
connector.
(6) Remove the bolts holding the Viscous Heater to
the mounting bracket.
(7) Remove the Viscous Heater from the vehicle.
REMOVAL - VISCOUS HEATER CLUTCH
(1) The viscous heater clutch can be serviced in
the vehicle and the cooling system does not have to
be drained.
(2) Disconnect and isolate the battery negative
cable.
(3) Remove the serpentine drive belt(Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
Fig. 17 CLUTCH ASSEMBLY- typical
1 - CLUTCH PLATE
2 - SHAFT KEY
3 - PULLEY
4 - COIL
5 - CLUTCH SHIMS
6 - SNAP RING
7 - SNAP RING
24 - 76 PLUMBINGWJ

(14) Remove the snap ring from the hub and
remove the clutch field coil (Fig. 22). Slide the clutch
field coil off of the hub.
INSTALLATION
INSTALLATION
(1) Install Viscous Heater to engine mounting
bracket.
(2) Install the Viscous Heater mounting bolts and
tighten to 33 N´m ( 25 ft. lbs.).
(3) Plug the wiring harness electrical connector to
the Viscous Heater clutch.
(4) Install heater hoses to the Viscous Heater con-
nections.
(5) Install heater hose clamps to Viscous Heater
connections.
(6) Install the engine accessory drive belt(Refer to
7 - COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION).
(7) Refill the engine cooling system(Refer to 7 -
COOLING/ENGINE - STANDARD PROCEDURE).
(8) Reconnect the battery negative cable.
(9) Operate vehicle and check for any coolant
leaks, repair as required.
INSTALLATION - VISCOUS HEATER CLUTCH
(1) Install the clutch field coil and snap ring.
(2) Install the screw and retainer on the clutch coil
lead wire harness on the viscous heater housing.
Tighten the screw to 2.2 N´m (20 in. lbs.)
(3) Align the rotor assembly squarely on the front
housing hub.
(4) Install the rotor bearing asembly with the
installer (Special Tool C-6871 or equalivent). Threadthe installer on the shaft, then turn the nut until the
rotor asembly is seated.
(5) Install the external front housing snap ring
with snap ring pliers. The bevel side of the snap ring
must be facing outward. Press the snap ring to make
sure it is properly seated in the groove.
CAUTION: If the snap ring is not fully seated in the
groove it will vibrate out, resulting in a clutch fail-
ure and severe damage to the front housing of the
compressor.
(6) Install the original clutch shims on the shaft.
(7) Install the clutch plate. Install the shaft hex
nut and tighten to 15±20 N´m (11±15 ft. lbs.).
(8) Check the clutch air gap with a feeler gauge
(Fig. 23). If the gap does not meet specification, add
or substract shims as required. The air gap specifica-
tion if 0.41 to 0.79 millimeters (0.016 to 0.031 inch-
es).
NOTE: The air gap is determined by the spacer
shims. When installing an original, or a new clutch
assembly, try the original shims first. When install-
ing a new clutch (and not having the old shims
available) use a 1.0, 0.50 and 0.13 millimeter (0.040,
0.020 and 0.005 inch) shim from the new clutch
hardware package that is provided with the new
clutch.
(9) Reinstall the viscous heater to the mounting
bracket. Tighten the mounting screws to 33 N´m (25
ft. lbs.).
(10) Reinstall the battery negative cable.
Fig. 22 CLUTCH FIELD COIL SNAP RING REMOVE-
typical
1 - COIL
2 - SNAP RING PLIERS
Fig. 23 CHECK CLUTCH AIR GAP-typical
1 - FEELER GAUGE
24 - 78 PLUMBINGWJ
VISCOUS HEATER (Continued)

EVAPORATIVE EMISSIONS
TABLE OF CONTENTS
page page
EVAPORATIVE EMISSIONS
DESCRIPTION
DESCRIPTION - EVAPORATION CONTROL
SYSTEM............................24
DESCRIPTION - CCV SYSTEM...........25
DESCRIPTION - PCV SYSTEM...........25
OPERATION
OPERATION - 4.0L CCV SYSTEM.........26
OPERATION - 4.7L PCV SYSTEM.........26
SPECIFICATIONS
TORQUE - EVAPORATION SYSTEM.......27
CCV HOSE
DIAGNOSIS AND TESTING - CCV SYSTEM -
4.0L................................28
REMOVAL - FIXED ORIFICE FITTING........28
INSTALLATION - FIXED ORIFICE FITTING....29
EVAP/PURGE SOLENOID
DESCRIPTION.........................29
OPERATION...........................29
REMOVAL.............................29
INSTALLATION.........................29
FUEL FILLER CAP
DESCRIPTION.........................29
OPERATION...........................29REMOVAL.............................29
LEAK DETECTION PUMP
DESCRIPTION.........................30
OPERATION...........................31
DIAGNOSIS AND TESTING - ENABLING
CONDITIONS TO RUN EVAP LEAK
DETECTION TEST.....................32
REMOVAL.............................35
INSTALLATION.........................35
ORVR
DESCRIPTION.........................37
OPERATION...........................37
P C V VA LV E
DIAGNOSIS AND TESTING - PCV VALVE/PCV
SYSTEM - 4.7L.......................37
REMOVAL - PCV VALVE - 4.7L.............39
INSTALLATION - PCV VALVE - 4.7L.........39
VACUUM LINES
DESCRIPTION.........................39
VAPOR CANISTER
DESCRIPTION.........................39
OPERATION...........................39
REMOVAL.............................40
INSTALLATION.........................40
EVAPORATIVE EMISSIONS
DESCRIPTION
DESCRIPTION - EVAPORATION CONTROL
SYSTEM
The evaporation control system prevents the emis-
sion of fuel tank vapors into the atmosphere. When
fuel evaporates in the fuel tank, the vapors pass
through the control valve, through the fuel manage-
ment valve, and through vent hoses and tubes to a
charcoal filled evaporative canister. The canister tem-
porarily holds the vapors. The Powertrain Control
Module (PCM) allows intake manifold vacuum todraw vapors into the combustion chambers during
certain operating conditions.
Gas powered engines use a duty cycle purge sys-
tem. The PCM controls vapor flow by operating the
duty cycle EVAP purge solenoid. Refer to Duty Cycle
EVAP Canister Purge Solenoid.
When equipped with certain emissions packages, a
Leak Detection Pump (LDP) will be used as part of
the evaporative system for OBD II requirements.
Also refer to Leak Detection Pump.
Vehicles powered with gasoline engines are also
equipped with ORVR (On-Board Refueling Vapor
Recovery). Refer to ORVR for additional information.
25 - 24 EVAPORATIVE EMISSIONSWJ

NOTE: The evaporative system uses specially man-
ufactured lines/hoses. If replacement becomes nec-
essary, only use fuel resistant, low permeation
hose.
Certain components can be found in (Fig. 1).
DESCRIPTION - CCV SYSTEM
The 4.0L 6±cylinder engine is equipped with a
Crankcase Ventilation (CCV) system. The system
consists of:
²A fixed orifice fitting of a calibrated size. This
fitting is pressed into a rubber grommet located on
the top/rear of cylinder head (valve) cover (Fig. 2).
²a pair of breather tubes (lines) to connect the
system components.
²the air cleaner housing.
²an air inlet fitting (Fig. 2).
DESCRIPTION - PCV SYSTEM
The 4.7L V-8 engine is equipped with a closed
crankcase ventilation system and a Positive Crank-
case Ventilation (PCV) valve.
This system consists of:
Fig. 1 ORVR / LDP COMPONENTS
1 - FUEL TANK (LEFT SIDE) 6 - EVAP CANISTER
2 - FRAME RAIL (LEFT-REAR OUTSIDE) 7 - LDP FILTER
3 - FUEL VENT TUBE 8 - TWO-PIECE SUPPORT BRACKET
4 - FUEL FILL TUBE 9 - LEAK DETECTION PUMP (LDP)
5 - CONTROL VALVE
Fig. 2 CCV SystemÐ4.0L Engine
1 - AIR INLET FITTING
2 - FIXED ORIFICE FITTING
3 - CCV BREATHER TUBE (REAR)
4 - INT. MAN. FITTING
5 - CCV BREATHER TUBE (FRONT)
WJEVAPORATIVE EMISSIONS 25 - 25
EVAPORATIVE EMISSIONS (Continued)

²a PCV valve mounted to the oil filler housing
(Fig. 3). The PCV valve is sealed to the oil filler
housing with an o-ring.
²the air cleaner housing
²two interconnected breathers threaded into the
rear of each cylinder head (Fig. 4).
²tubes and hose to connect the system compo-
nents.
OPERATION
OPERATION - 4.0L CCV SYSTEM
The CCV system performs the same function as a
conventional PCV system, but does not use a vacuum
controlled PCV valve.
The fixed orifice fitting meters the amount of
crankcase vapors drawn out of the engine.
When the engine is operating, fresh air enters the
engine and mixes with crankcase vapors. Engine vac-uum draws the vapor/air mixture through the fixed
orifice and into the intake manifold. The vapors are
then consumed during engine combustion.
OPERATION - 4.7L PCV SYSTEM
The PCV system operates by engine intake mani-
fold vacuum. Filtered air is routed into the crankcase
through the air cleaner hose and crankcase breath-
ers. The metered air, along with crankcase vapors,
are drawn through the PCV valve and into a passage
in the intake manifold. The PCV system manages
crankcase pressure and meters blow-by gases to the
intake system, reducing engine sludge formation.
The PCV valve contains a spring loaded plunger.
This plunger meters the amount of crankcase vapors
routed into the combustion chamber based on intake
manifold vacuum.
TYPICALPCV valves are shown in (Fig. 5), (Fig.
6) and (Fig. 7).
When the engine is not operating, or during an
engine pop-back, the spring forces the plunger back
against the seat (Fig. 5). This will prevent vapors
from flowing through the valve.
Fig. 3 PCV Valve/Oil Filler Tube (Housing)Ð4.7L
Engine
1 - O-RING
2 - LOCATING TABS
3 - CAM LOCK
4 - OIL FILLER TUBE
5 - PCV LINE/HOSE
6 - P C V VA LV E
Fig. 4 PCV System Hoses/TubesÐ4.7L Engine
1 - FRESH AIR FITTING
2 - CONNECTING TUBES/HOSES
3 - CRANKCASE BREATHERS (2)
4 - RUBBER HOSE
5 - AIR CLEANER RESONATOR
25 - 26 EVAPORATIVE EMISSIONSWJ
EVAPORATIVE EMISSIONS (Continued)

CCV HOSE
DIAGNOSIS AND TESTING - CCV SYSTEM -
4.0L
Before attempting diagnosis, be sure locations of
fixed orifice fitting and air inlet fitting (Fig. 8) have
not been inadvertently exchanged. The fixed orifice
fitting is light grey in color and is located atrearof
valve cover. The air inlet fitting is black in color and
is located atfrontof valve cover.
(1) Pull fixed orifice fitting (Fig. 8) from valve
cover and leave tube attached.
(2) Start engine and bring to idle speed.
(3) If fitting is not plugged, a hissing noise will be
heard as air passes through fitting orifice. Also, a
strong vacuum should be felt with a finger placed at
fitting inlet.
(4) If vacuum is not present, remove fitting orifice
fitting from tube. Start engine. If vacuum can now be
felt, replace fixed orifice fitting. Do not attempt to
clean plastic fitting.
(5) If vacuum is still not felt at hose, check line/
hose for kinks or for obstruction. If necessary, clean
out intake manifold fitting at intake manifold. Do
this by turning a 1/4 inch drill (by hand) through the
fitting to dislodge any solid particles. Blow out thefitting with shop air. If necessary, use a smaller drill
to avoid removing any metal from the fitting.
(6) Return fixed orifice fitting to valve cover and
leave tube attached.
(7) Disconnect air inlet fitting and its attached
hose at front of valve cover (Fig. 8). Start engine and
bring to idle speed. Hold a piece of stiff paper (such
as a parts tag) loosely over the rubber grommet
(opening) of the disconnected air inlet fitting.
(8) The paper should be drawn against the rubber
grommet with noticeable force. This will be after
allowing approximately one minute for crankcase
pressure to reduce.
(9) If vacuum is not present, check breather hoses/
tubes/lines for obstructions or restrictions.
(10) After testing, reconnect all system hoses/
tubes/lines.
REMOVAL - FIXED ORIFICE FITTING
When installing fixed orifice fitting, be sure loca-
tions of fixed orifice fitting and air inlet fitting (Fig.
9) have not been inadvertently exchanged. The fixed
orifice fitting is light grey in color and is located at
rearof valve cover. The air inlet fitting is black in
color and is located atfrontof valve cover.
(1) Pull fixed orifice fitting (Fig. 9) from valve
cover grommet.
(2) Separate fitting from CCV breather tube.
Fig. 8 Fixed Orifice Fitting and CCV SystemÐ4.0L
Engine
1 - AIR INLET FITTING
2 - FIXED ORIFICE FITTING
3 - CCV BREATHER TUBE (REAR)
4 - INT. MAN. FITTING
5 - CCV BREATHER TUBE (FRONT)
Fig. 9 FIXED ORIFICE FITTING - 4.0L
1 - AIR INLET FITTING
2 - FIXED ORIFICE FITTING
3 - CCV BREATHER TUBE (REAR)
4 - INT. MAN. FITTING
5 - CCV BREATHER TUBE (FRONT)
25 - 28 EVAPORATIVE EMISSIONSWJ

set a temporary fault without turning on the MIL
and continue the leak portion of the test. However,
the PCM will assume that the system is already
pressurized and skip the rapid pump cycles.
Always diagnose leaks, if possible, before discon-
necting connections. Disconnecting connections may
mask a leak condition.
Keep in mind that if the purge solenoid seat is
leaking, it could go undetected since the leak would
end up in the intake manifold. Disconnect the purge
solenoid at the manifold when leak checking. In addi-
tion, a pinched hose fault (P1486) could set if the
purge solenoid does not purge the fuel system prop-
erly (blocked seat). The purge solenoid must vent the
fuel system prior to the LDP system test. If the
purge solenoid cannot properly vent the system the
LDP cannot properly complete the test for P1486 and
this fault can set due to pressure being in the EVAP
system during the test sequence.
Multiple actuation's of the DRB IIItLeak Detec-
tion Pump (LDP) Monitor Test can hide a 0.020 leak
because of excess vapor generation. Additionally, any
source for additional vapor generation can hide a
small leak in the EVAP system. Excess vapor gener-
ation can delay the fall of the LDP diaphragm thus
hiding the small leak. An example of this condition
could be bringing a cold vehicle into a warm shop for
testing or high ambient temperatures.
Fully plugged and partially plugged underhood
vacuum lines have been known to set MIL condi-
tions. P1494 and P0456 can be set for this reason.
Always, thoroughly, check plumbing for pinches or
blockage before condemning components.
TEST EQUIPMENT The Evaporative Emission
Leak Detector (EELD) Miller Special Tool 8404 is
capable of visually detecting leaks in the evaporative
system and will take the place of the ultrasonic leak
detector 6917A. The EELD utilizes shop air and a
smoke generator to visually detect leaks down to
0.020 or smaller. The food grade oil used to make the
smoke includes an UV trace dye that will leave tell-
tale signs of the leak under a black light. This is
helpful when components have to be removed to
determine the exact leak location. For detailed test
instructions, follow the operators manual packaged
with the EELD.
NOTE: Be sure that the PCM has the latest software
update. Reprogram as indicated by any applicable
Technical Service Bulletin. After LDP repairs are
completed, verify the repair by running the DRB IIIT
Leak Detection Pump (LDP) Monitor Test as
described in Technical Service Bulletin 18-12-99.REMOVAL
The Leak Detection Pump (LDP) is located under
the left quarter panel behind the left/rear wheel (Fig.
16). It is attached to a two-piece support bracket
(Fig. 17). The LDP and LDP filter are replaced (ser-
viced) as one unit.
(1) Remove stone shield behind left/rear wheel
(Fig. 18). Drill out plastic rivets for removal.
(2) Remove 3 LDP mounting bolts (Fig. 19).
(3) Remove support bracket brace bolt (Fig. 17).
(4) Loosen, but do not remove 2 support bracket
nuts at frame rail (Fig. 19).
(5) To separate and lower front section of two-piece
support bracket, remove 3 attaching bolts on bottom
of support bracket (Fig. 17). While lowering support
bracket, disconnect LDP wiring clip (Fig. 20).
(6) Disconnect electrical connector at LDP (Fig.
20).
(7) Carefully remove vapor/vacuum lines at LDP
(Fig. 20).
(8) Remove LDP.
INSTALLATION
The LDP is located in the left quarter panel behind
the left/rear wheel. It is attached to a two-piece sup-
port bracket (Fig. 17). The LDP and LDP filter are
replaced (serviced) as one unit.
(1) Position LDP and carefully install vapor/vac-
uum lines to LDP and LDP filter.The vapor/vac-
uum lines and hoses must be firmly connected.
Fig. 16 LOCATION, LDP / EVAP CANISTER
1 - LEAK DETECTION PUMP
2 - EVAP CANISTER
WJEVAPORATIVE EMISSIONS 25 - 35
LEAK DETECTION PUMP (Continued)