What is a Coolant in a Car?

Coolant is more well knowns as antifreeze. It is either a bright yellow or green liquid that mixes with the water in your cars as well as trucks and other vehicles. The coolants main job is to keep the radiators from freezing or overheating. Made from either ethylene glycol or propylene glycol, antifreeze and coolant change the freezing and boiling points of water.

Engine coolant is actually a mixture of antifreeze and water and the ratio can vary from vehicle to vehicle. Antifreeze is not just for keeping cool either – engine coolant ensures that the water in your vehicle’s radiator system does not freeze in winter, or boil and evaporate in summer. It is a highly important product for the health of your vehicle.

A 50:50 mix of antifreeze and water is the most common. This mix raises the boiling point of water to between 240°C – 270°C and lowers the freezing point to around -37°C. However, don’t be tempted to fill up with pure antifreeze. Pure antifreeze actually has a much higher freezing point at around -20°C……

Does a Car Really Need Coolant?

Almost one third of the energy produced by the engine ends up as waste, this is either through the exhaust or as an excess heat energy. This excess heat energy must be cooled quickly to prevent engine overheating and a possible subsequent breakdown.
Coolant is pumped through the engine cooling system where the water absorbs excess heat energy. This is then carried through to the radiator. Through a process of heat exchange, the heat is removed and the water is cooled before it circulates the system once more.

With coolant or antifreeze in the cooling system, the water doesn’t freeze or boil under extreme temperatures. This ensure that the engine can be cooled effectively in any weather.

How Often Do I Need to Replace my Antifreeze?

Antifreeze does not expire, but the additives that prevent engine corrosion do. This means that the antifreeze must be changed to the manufacturer recommended guidelines. For some vehicles this can be every 30,000 miles.

It’s always good to get into the habit to regularly check that your coolant level is within the min/max marks on the coolant expansion tank. This can be found under the bonnet and be done in conjunction with you checking washer fluid and engine oil levels. N.B It can be easy to confuse coolant with washer fluid, but be very careful as these are two very different lubricants and you don’t want to get them mixed up!

If the coolant level is below the minimum mark, this could indicate a leak as most modern cars have sealed engine cooling systems. If this is the case, you should ask advice from our mechanics so they can nip this in the bud and before more costly engine problems develop.

How Do I Replace My Antifreeze?

If you do decide to replace it yourself…

• Ensure you replace like for like as different types of antifreeze are not compatible and do not mix well.
• Double check in your car manual which is the coolant filler cap, it can be an expensive mistake to put coolant in the washer fluid or engine oil tank so it’s worth making sure you’re in the right place!
• Last but not least, NEVER remove the coolant filler cap while the engine is hot. Coolant does get exceptionally hot and high engine pressures mean that releasing this cap when the engine isn’t cold could cause hot coolant to gush from the tank and potentially burn you.

Dec 8, 2019


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