The oil filter
removes most of the impurities that have been picked up by the oil, as it circulates
through the engine. Designed to be replaced readily, the filter is mounted in an
accessible location outside the engine.
There are two
basic filter element configurationsthe cartridge type and spin-on type.
cartridge-type element (fig. 6-24) fits into a permanent metal container. Oil is pumped
under pressure into the container where it passes from the outside of the filter element
to the center. From here, the oil exits the container. The element is changed easily by
removing the cover from the container.
spin-on filter (fig. 6-24)
is completely self-contained, consisting of an integral metal container and filter
element. Oil is pumped into the container on the outside of the filter element. The oil
then passes through the filter medium to the center of the element where it exits the
container. This type of filter is screwed onto its base and is removed by spinning it off.
themselves may be either metallic or nonmetallic. Cotton waste or resin-treated paper is
the most popular filter mediums. They are held in place by sandwiching them between two
perforated metal sheets. Some heavy-duty applications use layers of metal that are thinly
spaced apart. Foreign matter is strained out, as the oil passes between the metal layers.
There are two
filter configurations. These are the full-flow system and the bypass system. Operations of
each system is as follows:
full-flow system (fig. 6-25)
is the most oil filter to allow the oil to circulate through common. All oil in a
full-flow system is the system without passing through the element circulated through the
filter before it reaches the in the event that it becomes clogged. This engine. When a
full-flow system is used, it is prevents the oil supply from being cut off to the
necessary to incorporate a bypass valve in the engine.
bypass system (fig. 6-25)
diverts only a small quantity of oil each time it is circulated and returns it directly to
the oil pan after it is filtered. This type of system does not filter the oil before it is
sent to the engine. The oil from the main oil gallery enters the filter and flows through
the filter element. It then passes into the collector in the center of the filter. The
filtered oil then flows out a restricted outlet preventing the loss of pressure. The oil
then returns directly to the oil pan.
Figure 6-24.Oil filters.