63
Repair Instructions
Piston rings, inspection and
alignment
Checking piston ring gap
Check contact areas and sides. Black fleck on the
surfaces are due to bad contact and mean that the
rings should be replaced.
Oil consumption can also affect the moment that a
piston ring replacement should happen.
Check the piston ring gap (see illustration above).
When measuring the ring is slid down below the low-
er limit using a piston.
The piston rings are replaced if the gap exceeds the
stipulated values in the Workshop Manual “Technical
data”
Otherwise the piston rings are replaced if there a no-
ticeable wear (within wear tolerances) in the cylin-
ders, because the rings often return to the same posi-
tions that they were in before removal.
Check the piston ring gap on new rings as well. For
measurement details see, Workshop manual “Techni-
cal data” for engine variant.
Note.New cylinder liners are supplied complete with
pistons and piston rings.
Piston rings, installing
C
B
A
Install the piston rings on the piston using piston ring
pliers.
The oil ring (C) is installed first and can be freely
turned. The opening in the expander ring is placed op-
posite the oil ring gap.
The compression rings are marked. The lower
(chromed) ring (B) must have the marking TOPCD up-
wards.
Piston ring location all engines except
TAMD41H-B
Piston ring location TAMD41H-B
NOTE! TAMD41H-B are different to other engines.
These engines have a unique second compression
ring the internal chamfer of which should point down-
wards (other engines have the champfering upwards).
The upper keystone type ring (A) must be used with
the marking TOPCD upwards.
