How do engine coolants work?

Question

How do engine coolants work?

In: 1

Answer 1

Basically water that you send through the engine to cool it, then you take the hot water to a heat exchanger that cools the water using outside air.

The coolant can’t be simple water cause water is full of salt and at high temperature it becomes corrosive to metals. Coolant you buy is likely made with purified water and additives.

Additives can be chemicals that make water less corrosive.

then some other additive is present to prevent the water to freeze (more of it or less of it according to the temperatures of the place/country, the recommended temperature is written on the coolant container and should match the specs of your car manual, adjusted for local temperatures)

Then there are additives that may raise the boiling point so the coolant will not boil in the engine. Boiling creates vapors that create pressure and this pressure can blow a hole in a pipe or make other mechanical damage.

Then there are additives that keep the circuit clean. Imagine a sort of soap that prevents debris to build up in the pipes.

Distilled water is a decent substitute for coolant if you need it. But at that point, you are in a shop so just buy the coolant is a better option.

Tap water is usable in an emergency, not recomended long term. At the end of the emergency is better to drain the system and refill with proper coolant for all the above reasons.

For all this reasons, some engines are oil cooled or air cooled, it’s more common on machinery and aviation, and in both cases it’s a trade off, losing some performance in order to achieve higher reliability. Again water cooling is the cheapest way to cool powerful engines, not the most reliable.