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Ensurethebatteryiscompletelychargedandtheenginestartermotorisingood operating condition. Otherwise the
indicated compression pressures may not be valid for diagnosis purposes.
1. Clean the spark plug recesses with compressed air.
2. Remove the spark plugs.
3. Disable the fuel system (Refer to 14 - FUEL SYSTEM/FUEL DELIVERY - DESCRIPTION).
4. Remove the ASD relay (Refer to 8 - ELECTRICAL/IGNITION CONTROL/AUTO SHUTDOWNRELAY-
REMOVAL).
5. Insert a compression pressure gauge and rotate the engine with the engine starter motor for three revolutions.
6. Record the compression pressure on the 3rd revolution. Continue the test for the remaining cylinders.
7. (Refer to 9 - ENGINE - SPECIFICATIONS) for the correct engine compression pressures.
DIAGNOSIS AND TESTING - CYLINDERCOMBUSTION 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 seating).
Leaks between adjacent cylinders or into water jacket.
Any causes for combustion/compression pressure loss.
1. Check the coolant level and fill as required. DO NOT install the radiatorcap.
2. Start and operate the engine until it attains normal operating temperature, then turn the engine OFF.
3. Remove the spark plugs.
4. Remove the oil filler cap.
5. Remove the air cleaner hose.
6. Calibrate the tester according to the manufacturer’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) recommended.
7. Perform the test procedures on each cylinder according to the tester manufacturer’s instructions. Set piston of
cylinder to be tested at TDC compression,While testing, listen for pressurized air escaping through the throttle
body, tailpipe and 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 pressure, a minimum of 414 kPa (60 psi) should be maintained in the
cylinder.
Refer to CYLINDER COMBUSTION PRESSURE LEAKAGE DIAGNOSIS CHART .
CYLINDER COMBUSTION PRESSURE LEAKAGE DIAGNOSIS CHART
CONDITION POSSIBLE CAUSE CORRECTION
AIR ESCAPES THROUGH
THROTTLE BODYIntake valve bent, burnt, or not
seated properlyInspect valve and valve seat.
Reface or replace, as necessary.
Inspect valve springs. Replace as
necessary.
AIR ESCAPES THROUGH
TAILPIPEExhaust valve bent, burnt, or not
seated properlyInspect valve and valve seat.
Reface or replace, as necessary.
Inspect valve springs. Replace as
necessary.
AIR ESCAPES THROUGH
RADIATORHead gasket leaking or cracked
cylinder head or blockRemove cylinder head and inspect.
Replace defective part
MORE THAN 50% LEAKAGE
FROM ADJACENT CYLINDERSHead gasket leaking or crack in
cylinder head or block between
adjacent cylindersRemove cylinder head and inspect.
Replace gasket, head, or block as
necessary
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CONDITION POSSIBLE CAUSE CORRECTION
MORE THAN 25% LEAKAGE AND
AIR ESCAPES THROUGH OIL
FILLER CAP OPENING ONLYStuckorbrokenpistonrings;
cracked piston; worn rings and/or
cylinder wallInspect for broken rings or piston.
Measure ring gap and cylinder
diameter, taper and out-of-round.
Replace defective part as necessary
DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - LUBRICATION
CONDITION POSSIBLE CAUSES CORRECTION
OIL LEAKS 1. Gaskets and O-Rings. 1. Replace as necessary.
(a) Misaligned or damaged. (a) Replace as necessary.
(b) Loose fasteners, broken or
porous metal parts.(b) Tighten fasteners, Repair or
replace metal parts.
2. Crankshaft rear seal 2. Replace as necessary.
3. Crankshaft seal flange.
Scratched, nicked or grooved.3. Polish or replace crankshaft.
4. Oil pan flange cracked. 4. Replace oil pan.
5.Front cover seal, damaged or
misaligned.5. Replace seal.
6. Scratched or damaged vibration
damper hub.6. Polish or replace damper.
7. Crankshaft Rear Flange
Microporosity7. Replace Crankshaft
OIL PRESSURE DROP 1. Low oil level. 1. Check and correct oil level.
2. Faulty oil pressure sending unit. 2. Replace sending unit.
3. Low oil pressure. 3. Check pump and bearing
clearance.
4. Clogged oil filter. 4. Replace oil filter.
5. Worn oil pump. 5. Replace as necessary.
6. Thin or diluted oil. 6. Change oil and filter.
7. Excessive bearing clearance. 7. Replace as necessary.
8. Oil pump relief valve stuck. 8. Replace oil pump.
9. Oil pickup tube loose or
damaged.9. Replace as necessary.
OIL PUMPING AT RINGS; SPARK
PLUGS FOULING1. Worn or damaged rings. 1. Hone cylinder bores and replace
rings.
2. Carbon in oil ring slots. 2. Replace rings.
3. Incorrect ring size installed. 3. Replace rings.
4. Worn valve guides. 4. Ream guides and replace valves.
5. Leaking intake gasket. 5. Replace intake gaskets.
6. Leaking valve guide seals. 6. Replace valve guide seals.
DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - MECHANICAL
ENGINE MECHANICAL DIAGNOSIS CHART
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CONDITION POSSIBLE CAUSES CORRECTION
NOISY VALVES/LIFTERS 1. High or low oil level in crankcase 1. Check for correct oil level. Adjust
oil level by draining or adding as
needed
2. Thin or diluted oil 2. Change oil. (Refer to 9 -
ENGINE/LUBRICATION/OIL -
STANDARD PROCEDURE)
3. Low oil pressure 3. Check engine oil level. If ok,
Perform oil pressure test. (Refer to
9 - ENGINE/LUBRICATION -
DIAGNOSIS AND TESTING) for
engine oil pressure test/
specifications
4. Dirt in tappets/lash adjusters 4. Clean/replace hydraulic
tappets/lash adjusters
5. Bent push rod(s) 5. Install new push rods
6. Worn rocker arms 6. Inspect oil supply to rocker arms
and replace worn arms as needed
7. Worn tappets/lash adjusters 7. Install new hydraulic tappets/lash
adjusters
8. Worn valve guides 8. Inspect all valve guides and
replace as necessary
9. Excessive runout of valve seats
or valve faces9. Grind valves and seats
CONNECTING ROD NOISE 1. Insufficient oil supply 1. Check engine oil level.
2. Low oil pressure 2. Check engine oil level. If ok,
Perform oil pressure test. (Refer to
9 - ENGINE/LUBRICATION -
DIAGNOSIS AND TESTING) engine
oil pressure test/specifications
3. Thin or diluted oil 3. Change oil to correct viscosity.
(Refer to 9 - ENGINE/
LUBRICATION/OIL - STANDARD
PROCEDURE) for correct
procedure/engine oil specifications
4. Excessive connecting rod
bearing clearance4. Measure bearings for correct
clearance with plasti-gage. Repair
as necessary
5. Connecting rod journal out of
round5. Replace crankshaft or grind
journals
6. Misaligned connecting rods 6. Replace bent connecting rods
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CONDITION POSSIBLE CAUSES CORRECTION
MAIN BEARING NOISE 1. Insufficient oil supply 1. Check engine oil level.
2. Low oil pressure 2. Check engine oil level. If ok,
Perform oil pressure test. (Refer to
9 - ENGINE/LUBRICATION -
DIAGNOSIS AND TESTING)
3. Thin or diluted oil 3. Change oil to correct viscosity.
4. Excessive main bearing
clearance4. Measure bearings for correct
clearance. Repair as necessary
5. Excessive end play 5. Check crankshaft thrust bearing
for excessive wear on flanges
6. Crankshaft main journal out of
round or worn6. Grind journals or replace
crankshaft
7. Loose flywheel or torque
converter7. Inspect crankshaft, flexplate/
flywheel and bolts for damage.
Tighten to correct torque
LOW OIL PRESSURE 1. Low oil level 1. Check oil level and fill if
necessary
2. Faulty oil pressure sending unit 2. Install new sending unit
3. Clogged oil filter 3. Install new oil filter
4. Worn oil pump 4. Replace oil pump assembly.
5. Thin or diluted oil 5. Change oil to correct viscosity.
6. Excessive bearing clearance 6. Measure bearings for correct
clearance
7. Oil pump relief valve stuck 7. Remove valve to inspect, clean
and reinstall
8. Oil pickup tube loose, broken,
bent or clogged8. Inspect oil pickup tube and pump,
and clean or replace if necessary
9. Oil pump cover warped or
cracked9. Install new oil pump
OIL LEAKS 1. Misaligned or deteriorated
gaskets1. Replace gasket
2. Loose fastener, broken or porous
metal part2. Tighten, repair or replace the part
3. Front or rear crankshaft oil seal
leaking3. Replace seal
4. Leaking oil gallery plug or cup
plug4. Remove and reseal threaded
plug. Replace cup style plug
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CONDITION POSSIBLE CAUSES CORRECTION
EXCESSIVE OIL CONSUMPTION
OR SPARK PLUGS OIL FOULED1. CCV System malfunction 1. (Refer to 25 - EMISSIONS
CONTROL/EVAPORATIVE
EMISSIONS - DESCRIPTION) for
correct operation
2. Defective valve stem seal(s) 2. Repair or replace seal(s)
3. Worn or broken piston rings 3. Hone cylinder bores. Install new
rings
4. Scuffed pistons/cylinder walls 4. Hone cylinder bores and replace
pistons as required
5. Carbon in oil control ring groove 5. Remove rings and de-carbon
piston
6. Worn valve guides 6. Inspect/replace valve guides as
necessary
7. Piston rings fitted too tightly in
grooves7. Remove rings and check ring end
gap and side clearance. Replace if
necessary
STANDARD PROCEDURE
STANDARD PROCEDURE - REPAIR DAMAGED OR WORN THREADS
CAUTION: Be sure that the tapped holes maintain the original center line.
Damaged or worn threads can be repaired. Essentially, this repair consistsof:
Drilling out worn or damaged threads.
Tapping the hole with a special Heli-Coil Tap, or equivalent.
Installing an insert into the tapped hole to bring the hole back to its original thread size.
STANDARD PROCEDURE—HYDROSTATIC LOCK
CAUTION: DO NOT use the starter motor to rotate the crankshaft. Severe damage could occur.
When an engine is suspected of hydrostatic lock (regardless of what causedthe problem), follow the steps below.
1. Perform the Fuel Pressure Release Procedure (Refer to 14 - FUEL SYSTEM/FUEL DELIVERY - STANDARD
PROCEDURE).
2. Disconnect the negative cable(s) from the battery.
3. Inspect air cleaner, induction system, and intake manifold to ensure system is dry and clear of foreign material.
4. Place a shop towel around the spark plugs to catch any fluid that may possibly be under pressure in the cylinder
head. Remove the spark plugs.
5. With all spark plugs removed, rotate the crankshaft using a breaker bar and socket.
6. Identify the fluid in the cylinders (coolant, fuel, oil, etc.).
7. Be sure all fluid has been removed from the cylinders.
8. Repair engine or components as necessary to prevent this problem from occurring again.
9. Squirt a small amount of engine oil into the cylinders to lubricate the walls. This will prevent damage on restart.
10. Install new spark plugs. Tighten the spark plugs to 41 Nꞏm (30 ft. lbs.) torque.
11. Drain engine oil. Remove and discard the oil filter.
12. Install the drain plug. Tighten the plug to 34 Nꞏm (25 ft. lbs.) torque.
13. Install a new oil filter.
14. Fill engine crankcase with the specified amount and grade of oil. (Refer to LUBRICATION & MAINTENANCE -
SPECIFICATIONS).
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15. Connect the negative cable(s) to the battery.
16. Start the engine and check for any leaks.
REMOVAL
1. Perform the Fuel System Pressure Release proce-
dure (Refer to 14 - FUEL SYSTEM/FUEL DELIV-
ERY - STANDARD PROCEDURE).
2. Disconnect the battery negative cable.
3. Remove the air cleaner resonator and duct work as
an assembly.
4. Drain cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
5. Remove the viscous fan/drive (Refer to 7 - COOL-
ING/ENGINE/RADIATOR FAN - REMOVAL).
6. Remove the accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
7. Remove the fan shroud (3).
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8. Remove radiator (1) (Refer to 7 - COOLING/EN-
GINE/RADIATOR - REMOVAL).
9. Remove the upper crossmember and top core
support.
NOTE: It is not necessary to drain A/C system for
engine removal.
10. Remove the A/C compressor (2) with the lines
attached. Secure compressor out of the way.
Page 1768 of 5267
11. Remove generator assembly (2) (Refer to 8 -
ELECTRICAL/CHARGING/GENERATOR -
REMOVAL).
12. Remove the intake manifold and IAFM as an
assembly (Refer to 9 - ENGINE/MANIFOLDS/IN-
TAKE MANIFOLD - REMOVAL).
13. Disconnect the heater hoses.
NOTE: It is not necessary to disconnect P/S hoses
from pump, for P/S pump removal.
14. Remove the power steering pump and set aside.
15. Disconnect the fuel supply line (Refer to 14 -
FUEL SYSTEM/FUEL DELIVERY/QUICK CON-
NECT FITTING - STANDARD PROCEDURE).
16. Raise and support the vehicle on a hoist and
drain the engine oil.
17. Remove engine front mount thru-bolt nuts.
18. Remove right side axle retaining bolts.
19. Disconnect the transmission oil cooler lines from
their retainers at the oil pan bolts.
20. Disconnect exhaust pipe at manifolds (2).