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Checking Car Coolant: How to Stay Safe

Check your car coolant

Car coolant isn’t very complicated — it’s mostly ethylene glycol and typically mixed with water — but it can be one of the most dangerous fluids in your automobile. This is because your car’s cooling system is kept under pressure in order to maximize its efficiency, and whenever you are dealing with a pressurized liquid that’s hot enough to severely burn your skin, you need to be as careful as possible.

What’s the best way to check car coolant? Read on for tips and tricks to keep tabs on your coolant as safely as you can.

Never Open a Hot Radiator Cap
Radiator cap

The easiest way to verify how much coolant is in your radiator is to open the cap — but only when it’s cool. You should never open a hot-to-the-touch radiator cap, as you are risking a spray of pressurized coolant that could cause serious burns. Wait until your car’s engine has cooled down completely before opening the cap, or simply check the coolant level before turning on your engine. If you can see coolant in the radiator, and it’s near the top (approaching the cap spout), then you don’t need to add any additional antifreeze.

Use the Overflow Tank

This small tank is attached to the radiator with a hose, and many overflow tanks show a hot and cold fill line etched into the side. If the coolant sitting in the tank reaches one of those two marks, then you know there is enough in the entire system. Your overflow tank might have a cap for filling should you need to add more. Make sure to check your owner’s manual for your car’s specific procedure.

Check for Discoloration and Concentration

As the additives in your car coolant become used up after prolonged exposure to heat, it can turn the color darker, indicating it should be changed. You might also notice debris floating in the coolant, which typically results from deposits on the walls of the cooling system itself being flushed out. Either of these indicators means it’s time to flush and refill your car’s cooling system. It’s also worth using a small testing device to determine the freezing point of your coolant each fall to make sure it’s still concentrated enough to deal with the colder weather that’s approaching.

Checking your car’s coolant is certainly something you can do on your own—just be sure to take the proper safety precautions.

Check out all the chemical & lubricant products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on how to check car coolant, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Wikimedia Commons.

Benjamin Hunting View All

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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