21-3 Cylinder Liner, Pistons
Piston Rings, Measurement and
Inspection
1 Remove the piston rings with piston ring pliers.
2
Remove the piston pin retainer rings and remove
the piston pin carefully, using a suitable mandrel.
3 Check that the rings do not bind in the piston ring
grooves.
4 Check the piston ring gap. Push the ring down
below bottom dead center with a piston. Change
the piston ring if the gap exceeds 1.0 mm (0.04").
Also check the piston ring gap on new rings. Refer
to Group 21: Engine page 14
for measurements.
In general, piston rings should be changed if there
is any noticeable wear or out-of-roundness in the
cylinders, since piston rings frequently do not end
up in the same positions as they had before
removal.
Oil consumption is also of decisive importance for
the point in time when a piston ring change should
be done.
5 Check the clearance in the piston ring grooves.
Rotate the ring in its piston groove and measure
the clearance at several points with a feeler
gauge. Refer to Group 21: Engine page 14 for
measurements.
Piston and Cylinder Bore,
Inspection and Measurement
Check the pistons for cracks and worn piston ring
grooves. Change the piston if it has deep lines in the
skirt surface. Also if the piston has one or more cracks
in the piston pin hole. If any such damage is found, the
injection equipment must also be checked.
Measure the piston diameter with a micrometer at right
angles to the piston pin hole and 10 mm (0.4") from the
bottom edge of the piston. Then measure the cylinder
bore and calculate the clearance between the cylinder
and piston.
Replace the piston if the clearance exceeds permitted
values or if the piston diameter is lower than the per-
mitted value.
21-3 Cylinder Liner, Pistons
47701798 05-2013 © AB VOLVO PENTA 65
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