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19.4.13 C hecking/measuring
the
piston
D05033-
10
-
Check the piston
bearing
surface for damage.
»
If the
pist
on
bearing surface is
damaged:
-
Replace the
pist
on and, if
necessary,
the
cylinder.
-
Check that the piston
rings
move
easily
in the
piston ring
grooves.
»
If the piston ring is
sti
ff:
-
Clean the
piston ring
groove.
ENGINE 19
•
Tip
I
An old piston
ring
can
be used
t
o clean the
pis-
ton
ring
groove.
-
Check
the
piston rings
for
damage.
»
If the
piston ring is
damaged:
-
Change
the
piston ring.
•
Info
I
Mount the
piston ring
with the marking facing
upward.
-
Use the special
tool
to measure
c
learance
O
of
the
pist on
rings in the
piston ring
groove.
Guideline
Piston ring
-
groove
clearance
First ring (rectangular
s 0
.08 mm
(s
0.0031
in)
ring)
Second
r ing
(lower com-
s
0 .08 mm
(s
0.0031
in)
pression ring)
Oil
scraper
ring
s 0.06
mm
(s 0.0024 in)
I
Feeler gauge (59029041100)
(
~
p. 471)
•
If
clearance
O
is
larger
than the specified
value:
-
Change
the
piston and
piston rings.
-
Check/measure the cyl
inder.
(!..;..
p.
292)
-
Check
piston pin
for
discoloration, signs of wear
or
flaking of
the
coating.
•
If the piston pin
exhibits
significant discoloration/signs of
wec1r, or the coating is
flok ing:
-
Change
the
piston pin.
-
Place the
piston pin
in the connecting rod and check
the
seat-
ing
for
play.
•
If
the
pist
on pin seating has excessive play:
-
Change
the connecting
rod and
piston
pi
n.
293
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