Lesson 5/Learning Event 1
Oil. Lubricating oil helps to keep the engine running cool in two ways. First, it prevents a lot of heat from
being produced by friction. Second, it absorbs and carries heat away from parts, such as the pistons and
cylinder walls, as it comes in contact with them.
Exhaust. The exhaust system aids cooling by carrying hot exhaust gases away from the engine. You have
probably already noticed how hot the exhaust is that comes out of the exhaust system on a vehicle. All three
of these methods put together do not even come close to cooling the engine as much as needed. The rest of
the unwanted heat is carried away by the cooling system.
LIQUID-COOLING SYSTEM
At sometime, everyone has cooled something that was too hot by either blowing on it or pouring water over it.
Both of these two methods are used in liquid-cooling systems. For a more detailed understanding of how this
is done, let's discuss the different parts of the cooling system.
Coolant Jacket
You could think of a basic engine as each cylinder and combustion chamber being a separate part, and then all
of them enclosed by one container. Thus, if the container is filled with water, the cylinders and combustion
chambers would be completely surrounded by a jacket of coolant.
In actual practice, the engine block contains the cylinders which are surrounded by coolant passages. The
combustion chambers in the cylinder head also have coolant passages all around them. Coolant transfer ports in
the block, head, and head gasket align when the head is bolted to the block so the coolant can flow between
the block and head. When coolant is placed in these passages, the cylinders and combustion chambers are then
surrounded by a jacket of coolant, generally known as a water jacket.
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