Understanding Cooling Systems

Overheated Engine

Most of the energy in the gasoline is converted into heat. It is the job of cooling systems to take care of that heat. Therefore the cooling system is quite an important part of the vehicle. In fact, the cooling system on a vehicle that is driving down the freeway will dissipate enough heat to be able to heat two average-sized houses. Thus the main job of the cooling system is to keep the engine from overheating. It does this by transferring this heat to the air.

The cooling system also has some other important jobs.

The engine in your vehicle runs best at a fairly high temperature. When the engine is cold, the components will wear out faster, and the engine is less efficient and will emit more pollution. Therefore, the job of the cooling system here is to allow the engine to heat up as quickly as possible, and then to keep the engine at a constant temperature.

Fuel is constantly burning inside your vehicle’s engine, and a lot of heat from this combustion goes right out the exhaust system. But, some of it will soak into the engine and heat it up.


The engine runs best when the coolant is about 200 deg F. It is at this temperature that:

  • The combustion chamber is hot enough to completely vaporize the fuel. It provides better combustion and reduces emissions.
  • The oil used to lubricate the engine is thinner, therefore the engine parts will move more freely and the engine will waste less power moving its own component around
  • The metal parts will wear less

You will find that vehicles have two kinds of cooling systems:

  • Liquid-cooled
  • Air-cooled

In a liquid cooled cooling system, the vehicle circulates a fluid through pipes and passageways in the engine. As this liquid passes through the hot engine it will absorb heat, and this then cools the engine. When the fluid leaves the engine, it will pass through a exchanger, or radiator, which will transfer the heat from the fluid to the air blowing through the exchanger.

Engine Cooling System Diagram

Air cooling systems are not often found in many modern vehicles. Instead of circulating fluid through the engine, the engine block is covered in aluminum fins that conduct the heat away from the cylinder. A powerful fan will then force the air over the fins, which then cools the engine by transferring the heat to the air.

There is a lot of plumbing involved in the cooling system. The pump sends fluid into the engine block, where it makes its way through passages in the engine around the cylinders. It will then return through the cylinder head. The thermostat is located where the fluid leaves the engine, and the plumbing around the thermostat will send the fluid back to the pump directly if the thermostat is closed. If however, the thermostat is open, the fluid will go through the radiator first and then back to the pump.

Radiators – Explained

About Roadkill Customs 313 Articles
Roadkill Customs has evolved into the de facto resource dedicated to low budget, back yard builders and do-it-yourself hot rodders...