Car Wars: Air-cooled vs. Water-cooled Engines

The engine is the most important part of any car- after all, it's what makes it go and you wouldn't have much of a car without one.

When it comes to choosing what kind of engine you want in a classic car you've got two choices: air-cooled or water-cooled (ok, you can also go for an electric engine conversion too, but I'm thinking original car engines here).

​There's plenty of strengths and weaknesses for both engines, and as with most things it may just come down to personal preference in the end. But let's take a look in more detail at some of the things to consider when choosing what kind of engine you want for your classic car project.

Why do Engines Need a Cooling System?

Internal combustion engines (what you're most likely to have in your car) operate at high temperatures. These engines need intense pressure and heat to "combust" or explode, which generates kinetic energy to make the car drive. Basically, if your engine isn't getting up to a high temperature it won't work properly. 

But, as it turns out, you can have too much of a good thing. Too much heat in the engine can cause parts of it to distort and/or melt which is, by all accounts, VERY BAD. That's why it needs to be cooled.

Air-cooled Engines

An air-cooled engine is cooled by, not unsurprisingly, air. A big fan and shaped cowling blows and directs air all around the engine.

STRENGTHS

• Light- without water to weigh it down, the engine is lighter, meaning it can go faster and uses less fuel.

• Warms up quickly- the engine works best at a high temperature, so the quicker it warms up the better performance

• No risk of leaks- no water means no leaks- one less thing to worry about

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• No maintenance required- no need to change the coolant or perished hoses​ 

WEAKNESSES

• Loud- the big fan is noisy and the air ducting amplifies the mechanical sounds of the engine

• Harder to work on- the air ducting makes it hard to access some parts of the engine

• Less Compact- The cylinders need to be spaced far enough apart for air to flow freely around them

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• Interior heating- it's harder to set up decent interior heating

Other Stuff to Consider

• All air-cooled engines are petrol which generally have bad fuel economy (on classic cars anyway)

• While it's true that the fan and ducting system needs less maintenance compared to water cooled systems, air-cooled engines need an oil drop every 3000 miles or so

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• People (some people, not the good kind) are a bit snobby about air-cooled engines, regarding them as the only "true" type of classic car. If you buy an air-cooled car, you too can be part of this "exclusive" club!

Some Notable Examples of Air-Cooled Cars

Porsche 917

Citroen 2CV

Tempo Matador

Water-cooled Engines

Water-cooled engines on classic cars are similar to air-cooled only, instead of air, water circulates around the engine. This makes it a bit more complicated as an enclosed system is needed to carry the water around the engine for cooling.

​As the very basic diagram above shows, water absorbs heat from the engine and it rises to the top into the cylinder head (Fun Science Fact: this is because as water heats up it becomes lighter).

​The water then passes through the radiator where it's cooled (with the help of a small fan) in order to trickle down to the bottom and repeat the process again. Antifreeze is added to the water to stop it from corroding the metal in the engine and freezing in extreme cold temperatures.

STRENGTHS

WEAKNESSES

• Compact- unlike an air-cooled engine, the cylinders don't need to be spaced far apart, so the engine can be smaller

• Efficiency- there is a fan attached to the radiator, but it's smaller and uses less power than the one on an air-cooled engine

• Easier to Work On- with no air ducting in the way

• Quieter- the water and jackets insulate the engine making it less noisy than an air-cooled

• Heavy- all that water can add some serious drag on your car

• Takes longer to heat up- meaning reduced performance, at least from starting the engine

• Water can change- air is always air, but water can freeze if it gets too cold or boil if it gets too hot

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• Maintenance required- you need to keep a look out for leaks, change the coolant regularly and replace any perished hoses

Other Stuff to Consider

• While the lack of air ducting makes it easier to access parts of the engine, water-cooled engines tend to have more electronics, making them harder to work on yourself at home (although not impossible!) without the use of diagnostic equipment.

Some Notable Examples of Water-Cooled Cars

Citroen H Van

Classic Mini

VW MK1 Golf

And the Winner Is...?

A tough call, but I'd say water-cooled has the edge. Even with the extra weight, hassle of maintenance and constant fear of springing a leak, water-cooled engines are more efficient and better equipped to deal with the demands of modern life, which is probably why all engines are water-cooled these days! (Although, modern water-cooled engines are quite different from the classic ones I've described here).

That being said, in terms of classic car status air-cooled engines are definitely the most admired and the simplicity of them (if you can  get past the obstructive tinware!) makes them a top choice for car enthusiasts who enjoy working on their own vehicles.  

Got an opinion? Let us know in the comments

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