Content .. 268 269 270 271 ..

Subaru Legacy III (2000-2003 year). Manual - part 270

ME(H6DO)-68

MECHANICAL

CYLINDER BLOCK

2. CYLINDER AND PISTON

1) The cylinder bore size is stamped on the cylinder
block's front upper surface.

NOTE:
Measurement should be performed at a tempera-
ture 20

C (68

F).

NOTE:
Standard sized pistons are classified into two
grades, “A” and “B”. These grades should be used
as a guide line in selecting a standard piston.

Standard diameter:

A: 89.205 — 89.215 mm (3.5120 — 3.5124
in)
B: 89.195 — 89.205 mm (3.5116 — 3.5120
in)

2) How to measure the inner diameter of each cyl-
inder
Measure the inner diameter of each cylinder in both
the thrust and piston pin directions at the heights
shown in the figure, using a cylinder bore gauge.

CAUTION:
Measurement should be performed at a temper-
ature 20

°°°°

C (68

°°°°

F).

Taper:

Limit

0.050 mm (0.0020 in)

Out-of-roundness:

Limit

0.050 mm (0.0020 in)

3) When piston is to be replaced due to general or
cylinder wear, determine a suitable sized piston by
measuring the piston clearance.

(A) Main journal size mark

(B) Cylinder bore size mark

ME-00585

#6
#5
#4
#3
#2
#1

BBB

4
2B

( A )

( B )

( C )

(A) Thrust direction

(B) Piston pin direction

ME-00586

10 (0.39)

45 (1.77)

80 (3.15)

Unit: mm (in)

( A )

( B )

ME(H6DO)-69

MECHANICAL

CYLINDER BLOCK

4) How to measure the outer diameter of each pis-
ton
Measure the outer diameter of each piston at the
height shown in the figure. (Thrust direction)

CAUTION:
Measurement should be performed at a temper-
ature of 20

°°°°

C (68

°°°°

F).

Piston grade point H:

39.0 mm (1.535 in)

Piston outer diameter:

Standard

A: 89.185 — 89.195 mm
(3.5112 — 3.5116 in)
B: 89.175 — 89.185 mm
(3.5108 — 3.5112 in)

0.25 mm (0.0098 in) oversize

89.425 — 89.435 mm
(3.5207 — 3.5211 in)

0.50 mm (0.0197 in) oversize

89.675 — 89.685 mm
(3.5305 — 3.5309 in)

5) Calculate the clearance between cylinder and
piston.

CAUTION:
Measurement should be performed at a temper-
ature of 20

°°°°

C (68

°°°°

F).

Cylinder to piston clearance at 20

°°°°

C (68

°°°°

F):

Standard

0.010 — 0.030 mm (0.0004 — 0.0012 in)

Limit

0.050 mm (0.0020 in)

6) Boring and honing

(1) If the value of taper, out-of-roundness, or
cylinder-to-piston clearance measured exceeds
the specified limit or if there is any damage on
the cylinder wall, rebore it to use an oversize pis-
ton.

NOTE:
When any of the cylinders needs reboring, all other
cylinders must be bored at the same time, and use
oversize pistons. Do not perform boring on one cyl-

inder only, nor use an oversize piston for one cylin-
der only.

(2) If the cylinder inner diameter exceeds the
limit after boring and honing, replace the crank-
case.

NOTE:
Immediately after reboring, the cylinder diameter
may differ from its real diameter due to temperature
rise. Thus, pay attention to this when measuring
the cylinder diameter.

Limit of cylinder enlarging (boring):

0.5 mm (0.020 in)

3. PISTON AND PISTON PIN

1) Check pistons and piston pins for damage,
cracks, and wear and the piston ring grooves for
wear and damage. Replace if defective.
2) Measure the piston-to-cylinder clearance at
each cylinder. <Ref. to ME(H6DO)-68, CYLINDER
AND PISTON, INSPECTION, Cylinder Block.> If
any of the clearances is not to specification, re-
place the piston or bore the cylinder to use an over-
size piston.
3) Make sure that piston pin can be inserted into
the piston pin hole with a thumb at 20

C (68

F). Re-

place if defective.

Standard clearance between piston pin and
hole in piston:

Standard

0.004 — 0.008 mm (0.0002 — 0.0003 in)

Limit

0.020 mm (0.0008 in)

ME-00587

ME-00588

ME-00589

ME(H6DO)-70

MECHANICAL

CYLINDER BLOCK

4) Check circlip installation groove on the piston for
burr. If necessary, remove burr (A) from the groove
so that piston pin can lightly move.

5) Check piston pin circlip for distortion, cracks and
wear.

4. PISTON RING

1) If piston ring is broken, damaged, or worn, or if
its tension is insufficient, or when the piston is re-
placed, replace piston ring with a new one of the
same size as the piston.

CAUTION:
• Marks are shown on the end of the top and
second rings. When installing the rings to the
piston, face this mark upward.
• The oil ring is a combined ring consisting of
two rails and a spacer in between. When install-
ing, be careful to assemble correctly.

2) Squarely place piston ring and oil ring in cylin-
der, and measure the piston ring gap with a thick-
ness gauge.

3) Measure the clearance between piston ring and
piston ring groove with a thickness gauge.

CAUTION:
Before measuring the clearance, clean the pis-
ton ring groove and piston ring.

(A) Top ring

(B) Second ring

(a) Upper rail

(b) Expander

( A )

ME-00590

ME-00591

( a )

( c )

( b )

( A )

( B )

( C )

Unit: mm (in)

Standard

Limit

Piston
ring gap

Top ring

0.20 — 0.35

(0.0079 — 0.0138)

1.0 (0.039)

Second
ring

0.35 — 0.50

(0.0138 — 0.0197)

1.0 (0.039)

Oil ring
rail

0.20 — 0.60

(0.0079 — 0.0236)

1.5 (0.059)

Unit: mm (in)

Standard

Limit

Clearance
between pis-
ton ring and
piston ring
groove

Top ring

0.040 — 0.080

(0.0016 —

0.0031)

0.15 (0.0059)

Second
ring

0.030 — 0.070

(0.0012 —

0.0028)

0.15 (0.0059)

Clearance between oil
ring and oil ring groove

0.065 — 0.155

(0.0026 —

0.0061)

—

ME-00592

ME-00593

ME(H6DO)-71

MECHANICAL

CYLINDER BLOCK

5. CONNECTING ROD

1) Replace connecting rod, if the large or small end
thrust surface is damaged.
2) Check for bend or twist using a connecting rod
aligner. Replace connecting rod if the bend or twist
exceeds the limit.

Limit of bend or twist per 100 mm (3.94 in) in
length:

0.10 mm (0.0039 in)

3) Install connecting rod fitted with bearing to
crankshaft and measure the side clearance (thrust
clearance). Replace connecting rod if the side
clearance exceeds the specified limit.

Connecting rod side clearance:

Standard

0.070 — 0.330 mm (0.0028 — 0.0130 in)

Limit

0.4 mm (0.016 in)

4) Inspect connecting rod bearing for scar, peeling,
seizure, melting, wear, etc.
5) Measure the oil clearance on individual connect-
ing rod bearings by means of plastigauge. If any oil
clearance is not within specification, replace the
defective bearing with a new one of standard size
or undersize as necessary. (See the table below.)

Connecting rod oil clearance:

Standard

0.020 — 0.046 mm (0.0008 — 0.0018 in)

Limit

0.050 mm (0.0020 in)

(A) Thickness gauge

(B) Connecting rod

( A )

( B )

( A )

( B )

ME-00594

ME-00595

Unit: mm (in)

Bearing

Bearing size

(Thickness at cen-

ter)

Outer diameter of

crank pin

Standard

1.490 — 1.502

(0.0587 — 0.0591)

51.984 — 52.000

(2.0466 — 2.0472)

0.03

(0.0012)

undersize

1.510 — 1.513

(0.0594 — 0.0596)

51.954 — 51.970

(2.0454 — 2.0461)

0.05

(0.0020)

undersize

1.520 — 1.523

(0.0598 — 0.0600)

51.934 — 51.950

(2.0446 — 2.0453)

0.25

(0.0098)

undersize

1.620 — 1.623

(0.0638 — 0.0639)

51.734 — 51.750

(2.0368 — 2.0374)

Content .. 268 269 270 271 ..