Different Types of Cooling Systems -

There are two types of cooling systems; liquid cooling and air cooling. Most auto engines are cooled by the liquid type; air cooling is used more frequently for airplanes, motorcycles and lawnmowers.
Liquid cooled engines have passages for the liquid, or coolant, through the cylinder block and head. The coolant has to have indirect contact with such engine parts as the combustion chamber, the cylinder walls, and the valve seats and guides. Running through the passages in the engine heats the coolant (it absorbs the heat from the engine parts), and going through the radiator cools it. After getting "cool" again in the radiator, the coolant comes back through the engine. This business continues as long as the engine is running, with the coolant absorbing and removing the engine's heat, and the radiator cooling the coolant.

1) AIR COOLED ENGINES:
First when automobiles were invented they were air- cooled. But this did not last very long, they had problems of getting heated up when subjected to loads, climbing hills or travelling continuously.
2) WATER -COOLED ENGINES:
So then, finally water- cooled engines were invented, which had a radiator & water jackets in its engine block. This lasted for over a century, they were the most accepted internal combustion engine till the 1970's.
3) COOLANT COOLED ENGINES:
This was the successor of the very popular water -cooled engine.
Water cooled engines has many drawbacks, such as:
The water in the internal combustion engine evaporates in the engine jackets leaving behind steam, which in turn develops pressure that tries to escape through the hose pipes & the radiator, as a result of this there are portions of area which are not cooled & partially cooled. This in long run leads to micro cracks, fractures in the casting of the engine blocks & scaling, sludge formation on the jackets of the engine walls. All the rust & sludge are then washed by the pressure of water which is running through the channels of the engine and then they finally settle in the radiator & the full system gets jammed. Which in turn gets the engine to over heat, which gets the oil consumption high. The high oil consumption leads to high carbon formation in the engine head & blocks the valves, valve seats in the engine head and increases your fuel consumption, decreases your pickup & performance of your vehicle. The heat generated in the engine expands the bore of the cylinders & the pistons which increase the wear and tear of the engine so in a matter of several thousand kilometers overhauling is must to keep the engine in running condition. So in the long run the cost of the coolant may be just the fraction of the cost, to maintain the engine not using coolants.
MODERN ENGINES: COOLANT COOLED ENGINES
Today most of the engines in use today, use coolants. People have realized that it is sensible to use coolants than spending your valuable time & money on repairs, maintenance works & overhauling of your vehicle engines. All the commercial vehicles, small cars, luxury cars, heavy weight Trucks, Truck trailers, crane machines, generators, tractors etc. All these vehicles have switched over to using coolants, in their O.E. (original equipment) as standard equipment on the new vehicles.