2003 JEEP GRAND CHEROKEE 1500

OPERATION
The master cylinder bore contains a primary and
secondary piston. The primary piston supplies
hydraulic pressure to the front brakes. The secondary
piston supplies hydraulic pressure to the rear brakes.
The master cylinder reservoir stores reserve brake
fluid for the hydraulic brake circuits.
DIAGNOSIS AND TESTING - MASTER
CYLINDER/POWER BOOSTER
NOTE: Inspect and repair any external fluid leaks
before performing test.
(1) Start engine and check booster vacuum hose
connections. A hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2)
Stop engine and shift transmission into Neutral.
(3) Pump brake pedal until all vacuum reserve in
booster is depleted.
(4) Press and hold brake pedal under light foot
pressure. The pedal should hold firm, if the pedal
falls away the master cylinder or HCU may be faulty
(internal leakage).
(5) Start engine and note pedal action. It should
fall away slightly under light foot pressure then hold
firm. If no pedal action is discernible, power booster,
vacuum supply, or vacuum check valve is faulty. Pro-
ceed to the POWER BOOSTER VACUUM TEST.
(6) If the POWER BOOSTER VACUUM TEST
passes, rebuild booster vacuum reserve as follows:
Release brake pedal. Increase engine speed to 1500
rpm, close the throttle and turn off the engine.
(7) Wait a minimum of 90 seconds and try brake
action again. Booster should provide two or more vac-
uum assisted pedal applications. If vacuum assist is
not provided, some component of the booster is faulty.
POWER BOOSTER VACUUM TEST
(1) Connect vacuum gauge to booster check valve
with short length of hose and T-fitting (Fig. 48).
(2) Start and run engine at curb idle speed for one
minute.
(3) Observe the vacuum supply. If vacuum supply
is not adequate, repair vacuum supply.
(4) Clamp hose shut between vacuum source and
check valve.
(5) Stop engine and observe vacuum gauge.
(6) If vacuum drops more than one inch HG (33
millibars) within 15 seconds, booster diaphragm,
check valve or check valve seal/grommet is faulty.
POWER BOOSTER CHECK VALVE TEST
(1) Disconnect vacuum hose from check valve.
(2)
Remove check valve and valve seal from booster.
(3) Use a hand operated vacuum pump for test.(4) Apply 51-67 kPa (15-20 in.) vacuum at large
end of check valve (Fig. 49).
(5) Vacuum should hold steady. If gauge on pump
indicates vacuum loss the check valve and seal
should be replaced.
Fig. 48 Typical Booster Vacuum Test Connections
1 - TEE FITTING
2 - SHORT CONNECTING HOSE
3 - CHECK VALVE
4 - CHECK VALVE HOSE
5 - CLAMP TOOL
6 - INTAKE MANIFOLD
7 - VACUUM GAUGE
Fig. 49 Vacuum Check Valve And Seal
1 - BOOSTER CHECK VALVE
2 - APPLY TEST VACUUM HERE
3 - VALVE SEAL
5 - 24 BRAKES - BASEWJ
MASTER CYLINDER (Continued)

(8) Start engine and let idle long enough to circu-
late power steering fluid through flow/pressure test
gauge.
(9) Shut off the engine and check the fluid level,
add fluid as necessary. Start engine again and let
idle.
(10) The initial pressure reading should be
345-552 kPa (50-80 psi). If pressure is higher inspect
the hoses for restrictions and repair as necessary.
(11) Increase the engine speed to 1500 RPM and
read the flow meter. The reading should be 2.4 - 2.8
GPM, if the reading is below this specification the
pump should be replaced.
CAUTION: This next step involves testing maximum
pump pressure output and flow control valve oper-
ation. Do not leave valve closed for more than three
seconds as the pump could be damaged.
(12) Close valve fully three times for three seconds
and record highest pressure indicated each time.All
three readings must be at pump relief pressure
specifications and within 345 kPa (50 psi) of
each other.
²Pressures above specifications but not within
345 kPa (50 psi) of each other, replace pump.
²Pressures within 345 kPa (50 psi) of each other
but below specifications, replace pump.
CAUTION: Do not force the pump to operate against
the stops for more than 2 to 4 seconds at a time
because, pump damage will result.
(13) Open the test valve and turn the steering
wheel to the extreme left and right positions against
the stops. Record the highest pressure reading at
each position. Compare readings to the pump specifi-
cations chart. If pressures readings are not within 50
psi. of each other, the gear is leaking internally and
must be repaired.
GEAR INLET SPECIFICATIONS 4.0L & 4.7L
ENGINERELIEF
PRESSURE   50FLOW RATE
(GPM)
4.0L 9653 kPa (1400 psi)
1500 RPM 2.4 - 2.8
GPM
4.7L 9653 kPa (1450 psi)
PUMP MOTOR SPECIFICATIONS 4.7L
ENGINERELIEF
PRESSURE   50FLOW RATE
(GPM)
4.7L 9653 kPa (1900 psi)1100 RPM 2.4-2.8
GPM Minium
@ 200 psi
DIAGNOSIS AND TESTING - 4.7L -
HYDRAULIC
The following procedures are used to test the oper-
ation of the power steering and hydraulic fan sys-
tems on the vehicle. This test will provide the gallons
per minute (GPM) or flow rate of the power steering
pump along with any maximum relief pressure. Per-
form test anytime a power steering system problem
is present. This test will determine if the power
steering pump, hydraulic fan, and power steering
gear are not functioning properly. It will also deter-
mine if the flow coming out of the hydraulic fan
motor is sufficient for the power steering gear. The
following pressure and flow test is performed using
the Power Steering Analyzer Tool kit 6815 (Fig. 2)
and Adapter kit 8630 (Fig. 3).
FLOW TEST - FLOW FROM POWER STEERING
PUMP
(1) Check the power steering belt to ensure it is in
good condition and adjusted properly.
(2) Connect the pressure gauge hose from the
Power Steering Analyzer to Tube 8630-2.
(3) Connect Adapter 8630-3 to Power Steering
Analyzer test valve end.
(4) Disconnect the high pressure hose from the
power steering pump.
(5) Connect Tube 8630-2 to the pump hose fitting.
(6) Connect the power steering hose from the fan
motor to Adapter 8630-3.
(7) Open the test valve completely.
(8) Start engine and let idle long enough to circu-
late power steering fluid through the flow/pressure
test gauge.
(9) Shut off the engine and check the fluid level,
add fluid ass necessary. Start engine again and let
idle.
(10) The initial pressure reading should be 483 -
690 kPa (70 - 100 psi). If pressure is higher inspect
the hoses for restrictions and repair as necessary.
Fig. 3 4.7L HYDRAULIC POWER STEERING TEST
ADAPTERS
WJSTEERING 19 - 5
STEERING (Continued)

(11) Increase the engine speed to 1100 rpm and
read the flow meter. The reading should be 2.6 GPM
minimum, if the reading is below this specification,
the pump should be replaced.
FLOW AND PRESSURE TEST - FLOW FROM
HYDRAULIC FAN MOTOR TO STEERING GEAR
(should be done if necessary after the Pump flow
test)
(1) Connect the pressure gauge hose from the
Power Steering Analyzer to Fitting 8630-1.
(2) Connect Adapter 8630-4 to Power Steering
Analyzer test valve end.
(3) Disconnect the high pressure hose from the
power steering gear.
(4) Connect Fitting 8630-1 to the high pressure
hose.
(5) Connect Adapter 8630-4 to the power steering
gear.
(6) Open the test valve completely.
(7) Start engine and let idle long enough to circu-
late power steering fluid through the flow/pressure
test gauge.
(8) Shut off the engine and check the fluid level,
add fluid ass necessary. Start engine again and let
idle.
(9) The initial pressure reading should be 345-552
kPa (50-80 psi). If pressure is higher inspect the
hoses for restrictions and repair as necessary.(10) Increase the engine speed to 1500 RPM and
read the flow meter. The reading should be 2.4 - 2.8
GPM if the reading is below this specification the fan
should be replaced.
CAUTION: This next step involves testing maximum
fan motor steering relief pressure. Do not leave the
valve closed for more than three seconds.
(11) Close the valve fully three times for three sec-
onds and record highest pressures indicated each
time. All three readings must be at fan motor steer-
ing relief pressures.
(12) Open the test valve and turn the steering
wheel to the extreme left and right positions against
the stops. Record the highest pressure readings at
each position. If pressure readings are not within 50
psi from each other, the gear is leaking internally
and must be repaired.
PUMP MOTOR SPECIFICATIONS 4.7L
ENGINERELIEF
PRESSURE   50FLOW RATE
(GPM)
4.7L 9653 kPa (1900 psi)1100 RPM 2.4-2.8
GPM Minium
@ 200 psi
19 - 6 STEERINGWJ
STEERING (Continued)

DIAGNOSIS AND TESTING - HYDRAULIC
PRESSURE TEST
An accurate tachometer and pressure test gauges
are required. Test Gauge C-3293-SP has a 300 psi
range and is used at all locations where pressures
exceed 100 psi.
Pressure Test Port Locations
Only two pressure ports are supplied on the trans-
mission case. The torque converter clutch apply and
release ports are located on the right side of the
transmission case (Fig. 2).
To determine the line pressure, there are two avail-
able methods. The DRBtscan tool can be used to
read line pressure from the line pressure sensor. The
second method is to install Line Pressure Adapter
8259 (Fig. 4) into the transmission case and then
install the pressure gauge and the original sensor
into the adapter. This will allow a comparison of the
DRBtreadings and the gauge reading to determe the
accuracy of the line pressure sensor. The DRBtline
pressure reading should match the gauge reading
within  10 psi.
In order to access any other pressure tap locations,
the transmission oil pan must be removed, the pres-
sure port plugs removed and Valve Body Pressure
Tap Adapter 8258-A (Fig. 5) installed. The extensions
supplied with Adapter 8258-A will allow the installa-
tion of pressure gauges to the valve body. Refer to
(Fig. 3) for correct pressure tap location identifica-
tion.
TEST PROCEDURE
All pressure readings should be taken with the
transmission fluid level full, transmission oil at the
normal operating temperature, and the engine at
1500 rpm. Check the transmission for proper opera-
tion in each gear position that is in question or if a
specific element is in question, check the pressure
readings in at least two gear positions that employ
that element. Refer to the Hydraulic Schematics at
the rear of this section to determine the correct pres-
sures for each element in a given gear position.
Fig. 2 Torque Converter Pressure Locations
1 - TCC RELEASE
2 - TO COOLER
3 - TCC APPLY
4 - FROM COOLER
5 - LINE PRESSURE SENSOR
Fig. 3 Pressure Tap Locations
Fig. 4 Line Pressure Adapter 8259
1 - LINE PRESSURE SENSOR PORT
2 - LINE PRESSURE SENSOR
3 - TOOL 8259
4 - PRESSURE TAP
WJAUTOMATIC TRANSMISSION - 545RFE 21 - 181
AUTOMATIC TRANSMISSION - 545RFE (Continued)

PAINT TOUCH-UP
DESCRIPTION
When a painted metal surface has been scratched
or chipped, it should be touched-up as soon as possi-
ble to avoid corrosion. For best results, use Mopart
Scratch Filler/Primer, Touch-Up Paints and Clear Top
Coat. Refer to Introduction group of this manual for
Body Code Plate information.
WARNING: USE AN OSHA APPROVED BREATHING
FILTER WHEN SPRAYING PAINT OR SOLVENTS IN
A CONFINED AREA. PERSONAL INJURY CAN
RESULT.
OPERATION
(1) Scrape loose paint and corrosion from inside
scratch or chip.
(2) Clean affected area with MopartTar/Road Oil
Remover, and allow to dry.
(3) Fill the inside of the scratch or chip with a coat
of filler/primer. Do not overlap primer onto good sur-
face finish. The applicator brush should be wet
enough to puddle-fill the defect without running. Do
not stroke brush applicator on body surface. Allow
the filler/primer to dry hard.
(4) Cover the filler/primer with color touch-up
paint. Do not overlap touch-up color onto the original
color coat around the scratch or chip. Butt the new
color to the original color, if possible. Do not stroke
applicator brush on body surface. Allow touch-up
paint to dry hard.
(5) On vehicles without clear coat, the touch-up
color can be lightly finesse sanded (1500 grit) and
polished with rubbing compound.
(6) On vehicles with clear coat, apply clear top coat
to touch-up paint with the same technique as
described in Step 4. Allow clear top coat to dry hard.
If desired, Step 5 can be performed on clear top coat.
WARNING: AVOID PROLONGED SKIN CONTACT
WITH PETROLEUM OR ALCOHOL ± BASED CLEAN-
ING SOLVENTS. PERSONAL INJURY CAN RESULT.
AVOID PROLONGED SKIN CONTACT WITH PETRO-
LEUM OR ALCOHOL ± BASED CLEANING SOL-
VENTS. PERSONAL INJURY CAN RESULT.
FINESSE SANDING/BUFFING &
POLISHING
DESCRIPTION
CAUTION: Do not remove more than .5 mils of
clearcoat finish, if equipped. Base coat paint must
retain clear coat for durability.
Use a Paint Thickness Gauge #PR-ETG-2X or equiv-
alent to determine film thickness before and after
the repair.
Minor acid etching, orange peel, or smudging in
clearcoat or single-stage finishes can be reduced with
light finesse sanding, hand buffing, and polishing.If
the finish has been finesse sanded in the past,
it cannot be repeated. Finesse sanding opera-
tion should be performed by a trained automo-
tive paint technician.
23 - 82 PAINTWJ

STANDARD PROCEDURE - COMPRESSOR
CLUTCH BREAK-IN
After a new compressor clutch has been installed,
cycle the compressor clutch approximately twenty
times (five seconds on, then five seconds off). During
this procedure, set the A/C Heater control in the
Recirculation Mode, the A/C button in the on posi-
tion, the blower motor switch in the highest speed
position, and the engine speed at 1500 to 2000 rpm.
This procedure (burnishing) will seat the opposing
friction surfaces and provide a higher compressor
clutch torque capability.
REMOVAL
The refrigerant system can remain fully-charged
during compressor clutch, pulley, or coil replacement.
The compressor clutch can be serviced in the vehicle.
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the serpentine drive belt. Refer to
Cooling for the procedures.
(3) Remove the bolt that secures the compressor
clutch to the compressor shaft (Fig. 5). A band-type
oil filter wrench may be used to secure the clutch
during bolt removal.
(4) Tap the clutch plate with a plastic mallet to
release it from the splines on the compressor shaft.
Remove the clutch plate and shim(s) from the com-
pressor shaft (Fig. 6).
CAUTION: Do not pry between the clutch plate
assembly and the pulley to remove it from the com-
pressor shaft. Prying may damage the clutch plate
assembly.(5) Remove the external snap ring that secures the
compressor clutch pulley to the nose of the compres-
sor front housing with snap ring pliers (Special Tool
C-4574) and slide the pulley assembly off of the com-
pressor (Fig. 7).
(6) Remove the screw and retainer from the clutch
coil lead wire harness on the compressor front hous-
ing.
Fig. 5 COMPRESSOR SHAFT BOLT
1 - COMPRESSOR CLUTCH PLATE
2 - COMPRESSOR SHAFT BOLT
Fig. 6 CLUTCH PLATE AND SHIM(S)
1 - COMPRESSOR SHAFT
2 - CLUTCH PLATE
3 - CLUTCH PLATE SHIM
Fig. 7 PULLEY SNAP RING
1 - SNAP RING
24 - 14 CONTROLSWJ
A/C COMPRESSOR CLUTCH (Continued)