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Figure 3-4.—Cylinder sleeves. | Up
Construction Mechanic Basic Volume 01 - Construction methods and practices | Next
Figure 3-8.—Aircooled crankcase. |
In liquid-cooled engines CYLINDER SLEEVES
or LINERS (fig. 3-4) are used to provide a wearing
surface, other than the cylinder block, for the pistons to
ride against. This is important for the following
reasons:
Alloys of steel can be used that wears longer than
the surfaces of the cylinder block. This increases
engine life while keeping production costs
down.
Because the cylinders wear more than any other
area of the block, the life of the block can be
greatly extended by using sleeves. When
overhaul time comes, the block can be renewed
by just replacing the sleeves.
Using a sleeve allows an engine to be made of
other materials, such as aluminum, by providing
the wearing qualities necessary for cylinders that
aluminum cannot.
There are two types of cylinder sleeves: the DRY-
TYPE and the WET-TYPE. A dry-type sleeve does
not contact the coolant. The dry-type sleeve is pressed
into a full cylinder that completely covers the water
jacket. Because the sleeve has the block to support it, it
can be very thin. The wet-type sleeve comes in direct
contact with the coolant. It is also press-fitted into the
cylinder. The difference is that the water jacket is open
in the block and is completed by the sleeve. Because it
gets no central support from the block, it is made thicker
Figure 3-5.—Cylinder sleeve casualties.
than a dry sleeve. Also because the sleeve completes
the water jacket, it must fit so it seals in the coolant. This
is accomplished by using a metallic sealing ring at the
top and a rubber sealing ring at the bottom. There are
three basic ways of securing the sleeves in the cylinder
block as follows:
Press in a sleeve that is tight enough to be held by
friction.
Provide a flange at the top of the block that locks
the sleeve into place when the cylinder head is
bolted into place. This is more desirable than a
friction fit, because it locks the sleeve tightly.
Cast the sleeve into the cylinder wall. This is a
popular means of securing a sleeve in an
aluminum block.
Whatever method is used to secure the sleeves, it is
very important for the sleeve to fit tightly. This is so the
sleeve can transfer heat effectively to the water jackets.
Most cylinder sleeve casualties are directly related
to a lack of maintenance or improper operating
procedures. Figure 3-5 shows two common types of
cylinder sleeve casualties: cracks and scoring. Both
types of casualties require replacement of the sleeve.
The cylinder block also provides the foundation for
the cooling and lubricating systems. The cylinders of a
liquid-cooled engine are surrounded by interconnecting
passages cast in the block. Collectively, these passages
form the WATER JACKET that allows the circulation
of coolant through the cylinder block and the cylinder
head to carry off excessive heat created by combustion.
The water jacket is accessible through holes machined
in the head and block to allow removal of the material
used for casting of the cylinder block. These holes are
called core holes and are sealed by CORE HOLE
PLUGS (freeze plugs). These plugs are of two types:
cup and disk. Figure 3-6 shows a typical installation of
these plugs.
Figure 3-6.—Core hole plugs installed in cylinder block.
3-5
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