Jeep Wrangler TJ. Manual - part 423

CAUTION: Use extreme caution when crankshaft
polishing is necessary to remove minor nicks and
scratches. The crankshaft seal flange is especially
machined to complement the function of the rear oil
seal.

(6) For bubbles that remain steady with shaft

rotation, no further inspection can be done until dis-
assembled.

(7) After the oil leak root cause and appropriate

corrective action have been identified, replace compo-
nent(s) as necessary.

ENGINE DIAGNOSIS

Engine diagnosis is helpful in determining the

causes of malfunctions not detected and remedied by
routine maintenance.

These malfunctions may be classified as either

mechanical (e.g., a strange noise), or performance
(e.g., engine idles rough and stalls).

Refer to the Engine Mechanical and the Engine

Performance diagnostic charts, for possible causes

and corrections of malfunctions (Refer to 9 - ENGINE
- DIAGNOSIS AND TESTING - MECHANICAL)
(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING
- PERFORMANCE).

For fuel system diagnosis, (Refer to 14 - FUEL

SYSTEM/FUEL DELIVERY

DIAGNOSIS AND

TESTING).

Additional tests and diagnostic procedures may be

necessary for specific engine malfunctions that can-
not be isolated with the Service Diagnosis charts.
Information concerning additional tests and diagno-
sis is provided within the following:

• Cylinder Compression Pressure Test

• Cylinder Combustion Pressure Leakage Test

• Engine Cylinder Head Gasket Failure Diagnosis

• Intake Manifold Leakage Diagnosis

• Lash Adjuster (Tappet) Noise Diagnosis

• Engine Oil Leak Inspection

ENGINE MECHANICAL

CONDITION

POSSIBLE CAUSES

CORRECTION

VALVETRAIN NOISE

1. High or low oil level in
crankcase.

1. Check and correct engine oil
level.

2. Thin or diluted oil.

2. Change oil to correct viscosity.

3. Thick oil

3. (a) Change engine oil and filter.

(b) Run engine to operating
temperature.

4. Low oil pressure.

4. Check and correct engine oil
level.

5. Dirt in tappets/lash adjusters.

5. Replace rocker arm/hydraulic
lash adjuster assembly.

6. Worn rocker arms.

6. Inspect oil supply to rocker arms.

7. Worn tappets/lash adjusters.

7. Install new rocker arm/hydraulic
lash adjuster assembly.

8. Worn valve guides.

8. Replace cylinder head assembly.

9. Excessive runout of valve seats
on valve faces.

9. Grind valve seats and valves.

10. Missing adjuster pivot.

10. Replace rocker arm/hydraulic
lash adjuster assembly.

ENGINE 2.4L

9 - 7

ENGINE 2.4L (Continued)

CONDITION

POSSIBLE CAUSES

CORRECTION

CONNECTING ROD NOISE

1. Insufficient oil supply.

1. Check engine oil level.

2. Low oil pressure.

2. Check engine oil level. Inspect oil
pump relief valve and spring.

3. Thin or diluted oil.

3. Change oil to correct viscosity.

4. Thick oil

4. (a) Change engine oil and filter.

(b) Run engine to operating
temperature.

5. Excessive bearing clearance.

5. Measure bearings for correct
clearance. Repair as necessary.

6. Connecting rod journal
out-of-round.

6. Replace crankshaft or grind
surface.

7. Misaligned connecting rods.

7. Replace bent connecting rods.

MAIN BEARING NOISE

1. Insufficient oil supply.

1. Check engine oil level.

2. Low oil pressure.

2. Check engine oil level. Inspect oil
pump relief valve and spring.

3. Thin or diluted oil.

3. Change oil to correct viscosity.

4. Thick oil

4. (a) Change engine oil and filter.

(b) Run engine to operating
temperature.

5. Excessive bearing clearance.

5. Measure bearings for correct
clearance. Repair as necessary.

6. Excessive end play.

6. Check thrust bearing for wear on
flanges.

7. Crankshaft journal out-of-round
or worn.

7. Replace crankshaft or grind
journals.

8. Loose flywheel or torque
converter.

8. Tighten to correct torque.

9 - 8

ENGINE 2.4L

ENGINE 2.4L (Continued)

CONDITION

POSSIBLE CAUSES

CORRECTION

OIL PRESSURE DROP

1. Low oil level.

1. Check engine oil level.

2. Faulty oil pressure sending unit.

2. Install new sending unit.

3. Low oil pressure.

3. Check sending unit and main
bearing oil clearance.

4. Clogged oil filter.

4. Install new oil filter.

5. Worn parts in oil pump.

5. Replace worn parts or pump.

6. Thin or diluted oil.

6. Change oil to correct viscosity.

7. Oil pump relief valve stuck.

7. Replace oil pump.

8. Oil pump suction tube loose.

8. Remove oil pan and install new
tube or clean, if necessary.

9. Oil pump cover warped or
cracked.

9. Install new oil pump.

10. Excessive bearing clearance.

10. Measure bearings for correct
clearance.

OIL LEAKS

1. Misaligned or deteriorated
gaskets.

1. Replace gasket(s).

2. Loose fastener, broken or porous
metal part.

2. Tighten, repair or replace the
part.

3. Misaligned or deteriorated cup or
threaded plug.

3. Replace as necessary.

OIL CONSUMPTION OR SPARK
PLUGS FOULED

1. PCV system malfunction.

1. Check system and repair as
necessary. (Refer to 25 -
EMISSIONS CONTROL/
EVAPORATIVE EMISSIONS/PCV
VALVE - DIAGNOSIS AND
TESTING)

2. Worn, scuffed or broken rings.

2. Hone cylinder bores. Install new
rings.

3. Carbon in oil ring slots.

3. Install new rings.

4. Rings fitted too tightly in grooves.

4. Remove rings and check
grooves. If groove is not proper
width, replace piston.

5. Worn valve guide(s).

5. Replace cylinder head assembly.

6. Valve stem seal(s) worn or
damaged.

6. Replace seal(s).

STANDARD PROCEDURE

REPAIR OF DAMAGED OR WORN THREADS

Damaged or worn threads (excluding spark plug

and camshaft bearing cap attaching threads) can be
repaired. Essentially, this repair consists of drilling
out worn or damaged threads, tapping the hole with
a special Heli-Coil Tap, (or equivalent) and installing
an insert into the tapped hole. This brings the hole
back to its original thread size.

CAUTION: Be sure that the tapped holes maintain
the original center line.

Heli-Coil tools and inserts are readily available

from automotive parts jobbers.

HYDROSTATIC LOCKED ENGINE

When an engine is suspected to be hydrostatically

locked, regardless of what caused the problem, the
following steps should be used.

ENGINE 2.4L

9 - 9

ENGINE 2.4L (Continued)

CAUTION: DO NOT use starter motor to rotate the
engine, severe damage may occur.

(1) Inspect

air

cleaner,

induction

system

and

intake manifold to insure system is dry and clear of
foreign material.

(2) Remove negative battery cable.
(3) Place a shop towel around the spark plugs

when removing them from the engine. This will catch
any fluid that may possibly be in the cylinder under
pressure.

(4) With all spark plugs removed, rotate engine

crankshaft using a breaker bar and socket.

(5) Identify the fluid in the cylinder(s) (i.e., cool-

ant, fuel, oil or other).

(6) Make sure all fluid has been removed from the

cylinders. Inspect engine for damage (i.e., connecting
rods, pistons, valves, etc.)

(7) Repair engine or components as necessary to

prevent this problem from re-occurring.

CAUTION: Squirt approximately one teaspoon of oil
into the cylinders, rotate engine to lubricate the cyl-
inder walls to prevent damage on restart.

(8) Install new spark plugs.
(9) Drain engine oil and remove oil filter.
(10) Install a new oil filter.
(11) Fill engine with specified amount of approved

oil.

(12) Connect negative battery cable.
(13) Start engine and check for any leaks.

ENGINE CORE AND OIL GALLERY PLUGS

Using a blunt tool such as a drift and a hammer,

strike the bottom edge of the cup plug. With the cup
plug rotated, grasp firmly with pliers or other suit-
able tool and remove plug (Fig. 2).

CAUTION: Do not drive cup plug into the casting as
restricted cooling can result and cause serious
engine problems.

Thoroughly clean inside of cup plug hole in cylin-

der block or head. Be sure to remove old sealer.
Lightly coat inside of cup plug hole with Mopar

Stud and Bearing Mount. Make certain the new plug
is cleaned of all oil or grease. Using proper drive
plug, drive plug into hole so that the sharp edge of
the plug is at least 0.5 mm (0.020 in.) inside the
lead-in chamfer.

It is not necessary to wait for curing of the sealant.

The cooling system can be refilled and the vehicle
placed in service immediately.

ENGINE GASKET SURFACE PREPARATION

To ensure engine gasket sealing, proper surface

preparation must be performed, especially with the
use of aluminum engine components and multi-layer
steel cylinder head gaskets.

Never use the following to clean gasket surfaces:

(Fig. 3)

• Metal scraper.

• Abrasive pad or paper to clean cylinder block

and head.

Fig. 2 Core Hole Plug Removal

1 - CYLINDER BLOCK
2 - REMOVE PLUG WITH PLIERS
3 - STRIKE HERE WITH HAMMER
4 - DRIFT PUNCH
5 - CUP PLUG

Fig. 3 Proper Tool Usage For Surface Preparation

1 - ABRASIVE PAD
2 - 3M ROLOC™ BRISTLE DISC
3 - PLASTIC/WOOD SCRAPER

9 - 10

ENGINE 2.4L

ENGINE 2.4L (Continued)

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