Isuzu KB P190. Manual — part 673

Engine Mechanical – V6

Page 6A1–213

Piston Inspection Procedure

1

Inspect the pistons for the following conditions:
•

eroded areas at the top of the piston (1),

•

piston pin retainer grooves for burrs (2),

•

worn piston pin bores or worn piston pins (3),

•

scuffed or damaged skirt coating (4),

•

ring grooves for cracks, nicks or burrs that may
cause binding (5), and

•

warped or worn ring lands.

2

Replace pistons that show any signs of damage or
excessive wear.

Figure 6A1 – 384

Piston Measurement

1

Measure piston width using the following procedure:

a

Using an outside micrometer, measure the
width of the piston at 30 mm below the crown
top (1), at the thrust surfaces of the piston,
perpendicular to the piston pin centreline.

b

Compare the measurement of the piston to its
original cylinder by subtracting the piston width
from the cylinder diameter.

c

Check your measurements with specifications,
refer to 5

Specifications.

d

If the clearance obtained through measurement
is greater than the provided specifications and
the cylinder bores are within specification,
replace the piston.

Figure 6A1 – 385

2

Measure the piston pin bore to piston pin (2)
clearances using the following procedure:

a

Piston pin bores and pins must be free of
varnish or scuffing.

b

Use an outside micrometer (1) to measure the
piston pin in the piston contact areas.

Figure 6A1 – 386

Engine Mechanical – V6

Page 6A1–214

3

Using an inside micrometer, measure the piston pin
bore (1). Compare the result with the piston pin
diameter and piston pin to piston pin bore clearance
listed in the specifications, refer to 5

Specifications.

4

If the clearance is excessive, determine which piece
is out of specification and replace as required.

5

Replace the piston if any of its dimensions are out of
specification.

6

If the new piston does not meet clearance
specifications, the cylinder block may need to be
oversized to 0.25 mm. There is only one size of
oversized pistons and rings available for service.

Figure 6A1 – 387

Piston Ring Measurement

1

Measure the piston ring end gap using the following
procedure:

a

Place the piston ring (1) in the area of the bore where
the piston ring will travel, approximately 25 mm below
the deck surface. Ensure the ring is square with the
cylinder bore by positioning the ring with the piston
head.

b

Measure the end gap of the piston ring with feeler
gauges (2), refer to 5 Specifications.

c

If the clearance exceeds the provided specifications,
the piston rings must be replaced.

d

Repeat the procedure for all piston rings.

Figure 6A1 – 388

2

Measure the piston ring side clearance using the
following procedure:

a

Roll the piston ring (1) entirely around the piston ring
groove. If any binding is caused by the ring groove,
dress the groove with a fine file. If any binding is
caused by a distorted piston ring, replace the ring.

b

With the piston ring on the piston, use feeler
gauges (2) to check clearance at multiple locations.

c

Compare the measurements with piston ring side
clearance listed in the specifications, refer to 5
Specifications.

d

If the clearance is greater than specifications, replace
the piston rings.

Figure 6A1 – 389

Engine Mechanical – V6

Page 6A1–215

3

There is a locating dimple (1) on the compression
rings. Install the compression rings with the dimple
facing up.

4

If the new ring does not reduce the clearance to the
correct specification, install a new piston.

5

If the new piston does not meet clearance
specifications, the cylinder block may need to be
oversized to 0.25 mm. There is only one size of
oversized pistons and rings available for service.

Figure 6A1 – 390

Connecting Rod Cleaning Procedure

1

Clean the connecting rods in solvent.

Safety glasses must be worn when using
compressed air.

2

Dry the connecting rod using compressed air.

3

Remove the connecting rod cap and clean the threads.

4

Remove the connecting rod bearing and discard. Never reuse a connecting rod bearing that has been used in a
running engine.

Connecting Rod Visual Inspection Procedure

1

Inspect the piston pin bushing (4) for scoring or
damage.

2

Inspect the connecting rod beam (1) for twisting or
bending.

3

Inspect the rod cap (2) for any nicks or damage
caused by possible interference.

4

Inspect for scratches or abrasion on the rod bearing
seating surface.

5

If the connecting rod bores contain minor scratches or
abrasions, clean the bores in a circular direction with
a light emery paper.

6

Retain the original bolts (3) for preliminary assembly.
They must be replaced for final assembly.

Figure 6A1 – 391

Engine Mechanical – V6

Page 6A1–216

Connecting Rod Measurement Procedure

Piston Pin End

N O T E

Measurements of all components should be
taken with the components at normal room
temperature.

1

Using an outside micrometer (1), take two
measurements of the piston pin (2) in the area of the
connecting rod contact.

Figure 6A1 – 392

2

Using an inside micrometer, measure the connecting
rod piston pin bore (1).

3

Subtract the piston pin diameter from the piston pin
bore.

4

Compare the clearance measurements listed in the
specifications, refer to 5

Specifications.

5

If the clearance is excessive, replace the piston pin. If
a new pin does not resolve the clearance problem,
replace the connecting rod.

Figure 6A1 – 393

Crankshaft Bearing End

N O T E

Measurements of all components should be
taken with the components at normal room
temperature.

1

Using an inside micrometer, measure the connecting
rod crankshaft bearing bore (1).

2

Compare the bore measurements listed in the
specifications, refer to 5

Specifications.

3

Replace the connecting rod if the bore is out of
specification. Do not recondition the connecting rod.

Figure 6A1 – 394