Lesson 4/Learning Event 1
The crankcase ventilation system (also known as the breathing system) plays an important part in the life of an
engine. It has the responsibility of removing the vapors that form in the crankcase. If not removed, these
vapors form sludge when mixed with the engine oil and destroy the lubricating qualities of the oil.
What are these vapors and where do they come from? Well, part of the vapors are plain water which collects
on the walls of the crankcase the same way water forms on the outside of a glass of iced tea. As you know,
when the air containing water vapors strikes the cold outside of an iced tea glass, the vapors condense and
form drops of water on the glass. The same thing happens in an engine. When the engine is running, the air
in the crankcase starts to heat up. When the heated air strikes the cooler sides of the oil pan and crankcase,
the moisture in the air condenses and falls as drops of water into the engine oil.
Excess fuel from the combustion chamber can travel by the piston rings and collect in the crankcase oil along
with the water. Even with an engine in good condition, some unburned fuel gets by the rings into the
crankcase, especially during the time the engine is being cranked or is being operated while it is cold. The driver
usually has the choke pulled out or is pumping the accelerator to supply the engine with more fuel. Much of
the fuel that is not burned winds up in the crankcase where it dilutes the oil.
We cannot prevent the water and fuel from getting into the lubricating oil, but we can remove most of both of
them through the crankcase ventilation system.
OPERATION OF LUBRICATION SYSTEMS
The lubrication system has the job of supplying all of the moving parts in an engine with oil. As you know,
the oil helps to reduce friction, clean the moving parts, and cool them by carrying off part of the heat. In the
case of the pistons and rings, the oil helps to seal off the combustion chamber and helps to prevent the burning
gases from entering the crankcase.
There are four types of lubrication systems used in internal combustion engines. They are the splash, the
combination splash and force feed, the force feed, and the full-force feed.
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