27
Design and Function
Piston rings
Each piston has two compression rings and an oil
ring.
The upper ring “A” is of the “Keystone” type (trapezi-
um shaped) The keystone is molybdenum coated and
should be used with the marking TOPCD upwards.
The other compression ring “B” (chromed) is a burred
“twist”-ring The ring is slightly tapered and has a
turned inner face which should be installed with the
TOPCF marking upwards.
NOTE! TAMD41H-B are different to other engines.
These engines have a unique second compression
ring of which the internal chamfer should point down-
wards.
The oil ring “C” (chromed) can be installed in either
way. The ring has two scraper edges which are
pressed against the cylinder walls, partly through its
own tension and partly through an expander spring on
the inside of the ring. The opening of the expander
ring should be placed on the opposite side of the gap
in the oil ring.
A
B
C
Cylinder liners
The cylinder liners are of the wet type and are re-
placeable. They are made of a special alloy cast iron
and are spun cast.
Four rubber O-rings are used as the cylinder liners
outer seals. The three lower rings (1, 2) are located in
machined grooves in the liner. The upper sealing
ring (3) seals under the liner flange by pressing the
flange down onto the liner against the collar in the
cylinder block. These rings are made of different ma-
terials. The two lower sealing rings (purple) are made
of fluroine rubber (FPM), the other ring is ethylene-
propene rubber (EPDM) and is black.
WARNING! Special safety precautions apply for
fluorine rubber exposed to high temperatures,
see page 8.
Piston ring location all engines except
TAMD41H-B
Piston ring location TAMD41H-B
