Dodge Dakota Sport 2001 Service Manual page 1100

AN
ENGINE 3.9L (Continued)
DIAGNOSIS AND TESTING—CYLINDER
COMBUSTION PRESSURE LEAKAGE
The combustion pressure leakage test provides an
accurate means for determining engine condition.
Combustion pressure leakage testing will detect:
• Exhaust and intake valve leaks (improper seat-
ing)
• Leaks between adjacent cylinders or into water
jacket
• Any causes for combustion/compression pressure
loss
WARNING: DO NOT REMOVE THE RADIATOR CAP
WITH THE SYSTEM HOT AND UNDER PRESSURE.
SERIOUS BURNS FROM HOT COOLANT CAN
OCCUR.
Check the coolant level and fill as required. DO
NOT install the radiator cap.
Start and operate the engine until it attains nor-
mal operating temperature, then turn OFF the
engine.
CYLINDER COMBUSTION PRESSURE LEAKAGE DIAGNOSIS CHART
CONDITION
AIR ESCAPES THROUGH
THROTTLE BODY
AIR ESCAPES THROUGH
TAILPIPE
AIR ESCAPES THROUGH
RADIATOR
MORE THAN 50% LEAKAGE
FROM ADJACENT CYLINDERS
MORE THAN 25% LEAKAGE AND
AIR ESCAPES THROUGH OIL
FILLER CAP OPENING ONLY
STANDARD PROCEDURE—CYLINDER BORE
HONING
Before honing, stuff plenty of clean shop towels
under the bores and over the crankshaft to keep
abrasive materials from entering the crankshaft
area.
(1) Used carefully, the Cylinder Bore Sizing Hone
C-823, equipped with 220 grit stones, is the best tool
for this job. In addition to deglazing, it will reduce
taper and out-of-round, as well as removing light scuff-
ing, scoring and scratches. Usually, a few strokes will
clean up a bore and maintain the required limits.
Remove the spark plugs.
Remove the oil filler cap.
Remove the air cleaner.
Calibrate the tester according to the manufactur-
er's instructions. The shop air source for testing
should maintain 483 kPa (70 psi) minimum, 1,379
kPa (200 psi) maximum and 552 kPa (80 psi) recom-
mended.
Perform the test procedure on each cylinder accord-
ing to the tester manufacturer's instructions. While
testing, listen for pressurized air escaping through
the throttle body, tailpipe or oil filler cap opening.
Check for bubbles in the radiator coolant.
All gauge pressure indications should be equal,
with no more than 25% leakage.
FOR EXAMPLE: At 552 kPa (80 psi) input pres-
sure, a minimum of 414 kPa (60 psi) should be main-
tained in the cylinder.
Refer to CYLINDER COMBUSTION PRESSURE
LEAKAGE DIAGNOSIS CHART below
POSSIBLE CAUSE
Intake valve bent, burnt, or not
seated properly
Exhaust valve bent, burnt, or not
seated properly
Head gasket leaking or cracked
cylinder head or block
Head gasket leaking or crack in
cylinder head or block between
adjacent cylinders
Stuck or broken piston rings;
cracked piston; worn rings and/or
cylinder wall
CAUTION: DO NOT use rigid type hones to remove
cylinder wall glaze.
(2) Deglazing of the cylinder walls may be done if
the cylinder bore is straight and round. Use a cylin-
der surfacing hone, Honing Tool C-3501, equipped
with 280 grit stones (C-3501-3810). about 20-60
strokes, depending on the bore condition, will be suf-
ficient to provide a satisfactory surface. Using honing
oil C-3501-3880, or a light honing oil, available from
major oil distributors.
ENGINE 3.9L
CORRECTION
Inspect valve and valve seat.
Reface or replace, as necessary
Inspect valve and valve seat.
Reface or replace, as necessary
Remove cylinder head and inspect.
Replace defective part
Remove cylinder head and inspect.
Replace gasket, head, or block as
necessary
Inspect for broken rings or piston.
Measure ring gap and cylinder
diameter, taper and out-of-round.
Replace defective part as necessary
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