Isuzu engine 4j series. Manual - part 24

6A – 32

  GENERAL ENGINE MECHANICAL

5. Timing Gear Housing

5a. Timing Pulley Housing

6. Oil Pump Assembly

7. Piston Cooling Oil Pipe

8. Piston and Connecting Rod

9. Flywheel

10. Cylinder Block Rear Plate

11. Crankshaft Rear Oil Seal (Gear and Belt Drive Model)

•

With the oil seal pushed in deep, install the special tool
as shown in the illustration to remove the oil seal.
Remover: Rear Oil Seal 5-8840-2360-0

NOTE:

Take care not to damage sealing surface of rear plate
and crankshaft when removing oil seal.

12. Main Bearing Cap

13. Crankshaft

INSPECTION AND REPAIR

Make the necessary adjustments, repairs, and part
replacements if excessive wear or damage is discovered
during inspection.

1. Crankshaft

Thrust clearance
Set the dial indicator as shown in the illustration and
measure the crankshaft thrust clearance.
If the thrust clearance exceeds the specified limit, replace
the thrust bearing as a set.
Thrust clearance

mm (in)

Standard

Limit

0.10 (0.0039)

0.30 (0.0118)

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GENERAL ENGINE MECHANICAL   6A – 33

2. Main bearing clearance

1) Remove the main bearing caps in the sequence

shown in the illustration.
Arrange the removed main bearing caps in the cylinder
number order.

2) Remove the crankshaft. Remove the main bearings.
3) Clean the upper and lower bearings as well as the

crankshaft main journal.

4) Check the bearings for damage or excessive wear.

The bearings must be replace as a set if damage or
excessive wear is discovered during inspection.

5) Set the upper bearings and the thrust washers to their

original positions. Carefully install the crankshaft.

6) Set the lower bearings to the bearing cap original

position.

7) Apply plastigage to the crankshaft journal unit as

shown in the illustration.

8) Install the main bearing caps. Apply engine oil to the

bolt threads and the seats. Tighten the bolts to the
specified torque.

N∙m (kg∙m/lb∙ft)

                                                                                                                   

167 (17/123)

                                                                                                                   

NOTE:

Do not allow the crankshaft to rotate.
9) Remove the main bearing caps.
10) Measure the plastigage width and determine the oil

clearance. If the oil clearance exceeds the specified
limit, replace the main bearings as a set and/or
replace the crankshaft.

11) Clean the plastigage from the bearings and the

crankshaft.

12) Remove the crankshaft and the bearings.
Oil Clearance

mm (in)

Standard

Limit

4JB1
/4JB1T
4JB1TC

0.035 - 0.080

(0.0014 - 0.0036)

4JG2

0.031 - 0.063

(0.0012 - 0.0025)

0.11 (0.0043)

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6A – 34

  GENERAL ENGINE MECHANICAL

3. Run-out

1) Carefully set the crankshaft on the V-blocks.

Slowly rotate the crankshaft and measure the runout.
If the crankshaft runout exceeds the specified limit, the
crankshaft must be replaced.

Run-Out

mm (in)

Standard

Limit

0.05 (0.0020)

or less

0.08 (0.0031)

Measure the diameter and the uneven wear of main
journal and crank pin.
If the crankshaft wear exceeds the specified limit,
crankshaft must be replaced.

mm (in)

Standard

Limit

Main journal
diameter

69.917-69.932

(2.7526 - 2.7532)

69.91 (2.7524)

Crank pin
diameter

52.915 - 52.930

(2.0833)

52.90 (2.0843)

Uneven wear
limit

0.05 (0.0020)

or less

0.08 (0.0031)

Crankshaft inspection

Inspect the surface of the crankshaft journals and crank
pins for excessive wear and damage.
Inspect the oil seal fitting surfaces for excessive wear and
damage.
Inspect the oil ports for obstructions.

Crankshaft tufftriding inspection

The portion to be tested must be held horizontally so as
not let the test solution flow.
Test liquid should not be applied to the area around the oil
port.
The sliding surface of the pin or journal.
Approximately 10mm

NOTE:

To increase crankshaft strength, Tufftride Method
(Soft nitriding) has been applied. Because of this, it is
not possible to regrind the crankshaft surfaces.
1. Use an organic cleaner to thoroughly clean the

crankshaft. There must be no traces of oil the surfaces
to be inspected.

2. Prepare a 5-10% solution of ammonium cupric

chloride (dissolved in distilled water).

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GENERAL ENGINE MECHANICAL   6A – 35

3. Use a syringe to apply the solution to the surface to be

inspected.
Hold the surface to be inspected perfectly horizontal to
prevent the solution from running.

NOTE:
Do not allow the solution to come in contact with the
oil ports and their surrounding area.

Testing
1. Wait for thirty to forty seconds.

If there is no discoloration after thirty or forty seconds,
the crankshaft is usable.
If discoloration appears (the surface being tested will
become the color copper), the crankshaft must be
replaced.

2. Steam clean the crankshaft surface immediately after

completing the test.

NOTE:
The ammonium cupric chloride solution is highly
corrosive. Because of this, it is imperative that the
surfaces being tested be cleaned immediately after
completing the test.

CRANKSHAFT BEARING SELECTION

When installing new crankshaft bearings or replacing old
bearings, refer to the selection table.

NOTE:

Please note that some Crankshaft No. 4 journals made
during a limited production period have their number
(No. 4) marked on either their front or rear side of
webs as shown below.

NOTE:

Although all upper journal bearings (cylinder body
side) have oil grooves and holes, all lower bearings
(bearing cap side) have no groove and hole.

Play close attention to the distinction during the
installation procedure.

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