Directing a portion of the exhaust through a
passage in the intake manifold (fig. 3-17). The
heat from the exhaust transfers and heats the
mixture. The amount of exhaust that is diverted
into the intake manifold heat passage is
controlled by the manifold heat control valve.
Directing the engine coolant, which is heated by
the engine, through the intake manifold on its
way to the radiator (fig. 3-18).
Gaskets (fig. 3-19), otherwise known as static seals,
are used to form pressure-tight joints between
stationary members. They are usually made of a
deformable material in the shape of a sheet or ring,
which conforms to the irregularities in mating surfaces
when compressed. Steel, aluminum, copper, asbestos,
cork, synthetic rubber, paper, and felt are just a few of
the materials that are used singly or in combination to
produce leakproof joints. The proper material used in
gasket construction depends on the temperature, type of
fluid to be contained, smoothness of mating surfaces,
fastener tension, pressure of the substance to be
confined, material used in construction of mating parts,
and part clearance relationship. Some of the most
common engine gaskets are as follows:
CYLINDER HEAD GASKET which is placed
between the cylinder head and the cylinder block
to maintain a gastight and coolant-tight seal. It is
made in the form of two thin plates of soft metal
with asbestos tilling between them.
Figure 3-17.Exhaust-heated intake manifold.
INTAKE AND EXHAUST GASKETS are
made from asbestos and formed to a desired
shape. Some of them are metal-covered and
similarin construction to a cylinder head gasket.
OIL PAN GASKET is generally made from
pressed cork. It may be made in one piece but is
often made as two pieces.
Gaskets also can be formed by using a silicone
sealant. This type is formed by applying sealant from a
squeeze tube to the mating surfaces and allowing it to
dry, forming a sealed flexible joint. This type of seal is
becoming more popular on modern vehicles.
Oil seals used in vehicle assembly are designed to
prevent leakage between rotating and non-rotating
Figure 3-18.Water-heated intake manifold.