• Ashley Bradish

Cool it!- with Coolant

Updated: Aug 2

Last month, we went over vehicle A/C systems and some common questions you may have had about them. But the hot weather is just getting started, so let's talk about your coolant.

What does coolant do?

Coolant Being Poured Into the Reservoir

Coolant prevents the engine and underhood from overheating. It travels back and forth from the engine to the radiator to keep the temperature low in more than one spot.

But coolant does more than protect your engine from heat. Coolant contains antifreeze, which prevents your engine from freezing. It does so by lowering the water's freezing point, so it's harder for the water to crystalize. It's like how coolant raises the boiling point of water to prevent overheating. Without enough antifreeze, an engine would freeze up every time it got cold outside.

I know what you're thinking: "How could coolant prevent freezing?" Well, that's where the antifreeze comes in. Coolant is a blend of water and antifreeze, usually a 50/50 ratio. Antifreeze has ethylene glycol (C2H6O2) or propylene glycol (C3H8O2).

Ethylene glycol and propylene glycol are very similar and great at preventing corrosion. The only difference between the two is that propylene glycol is a bit less effective at lowering the freezing point.

Antifreeze has to be diluted with water before use, thus making coolant. Pure antifreeze will not fight corrosion, freezing, or overheating as efficiently.

You also can't use water to replace coolant. Water alone won't prevent freezing and, in the summer, overheating.

Coolant and antifreeze have corresponding purposes, but they are not the same. Think of antifreeze as an ingredient in your coolant recipe.

What's the difference between Coolant and Refrigerant?

Freon Refrigerant Container Compared to Coolant Reservoir

So now we know the difference between coolant and antifreeze. But what's the difference between coolant and refrigerant?

They may sound like they would be the same, but Coolant and Refrigerant are very different fluids. As you've read above, coolant keeps the temperature low under the hood. Meanwhile, refrigerant controls the temperature inside the vehicle's cabin, AKA where you are.

Refrigerant is a crucial part of your A/C system that absorbs heat. It cycles between a gas and liquid state to continuously provide cold air.

If you want to learn more about refrigerants, read our blog on Air Conditioning.

How do I know if I'm leaking coolant?

Coolant Leak

Did you know that around 75% of coolant sold in the U.S. is because of leaks? If your vehicle is leaking coolant, have a technician repair it before the low levels cause damage.

Common causes of coolant loss include:

  • External leaks from radiator hoses, connections between hoses, or from the radiator itself

  • A radiator cap leak from a faulty seal

  • Internal leaks from areas where coolant can leak out, i.e., an engine head gasket.

If you top-off your coolant, make sure you are using the correct kind. Different vehicles need different coolants. There's pink, blue, yellow, etc. Some concentrated, some diluted; some can mix, some cannot.

What would happen if my car ran out of coolant?