As the name suggests, coolant keeps your engine cool—but does that mean it’s impervious to flames? With so many complex chemicals swirling around your vehicle, it’s understandable that novice drivers wonder if coolant has a flashpoint. If you’re curious about this significant safety issue, please read through the research we’ve done on engine coolant flammability.
Engine coolant is a flammable substance. Even though coolant is mixed with water, it can ignite when exposed to high temperatures or flames. If you ever notice signs of a coolant leak, please take your car to a mechanic for a thorough screening.
Many people are surprised to learn engine coolant is flammable. After all, how could you ignite something that has water in it? If you are curious to learn more about coolant safety, be sure to read through the information that we’ve compiled below.
How Dangerous Is Engine Coolant?
Engine coolant may seem benign, but it can burn if you’re not careful. In this first section, we’ll explain what makes coolant dangerous and how it could burn your vehicle.
How Is It Possible That Engine Coolant Is Flammable?
The reason engine coolant is flammable has to do with a compound known as glycol. Interestingly, this clear and sweet-smelling chemical has a remarkably low freezing point, which makes it incredible at extending water’s range of heat transfer.
One of the downsides of glycol is that it could ignite when exposed to very high temperatures. Even though there’s water in your antifreeze solution, it could eventually burn off and cause glycol to “auto-ignite.” Firefighters explain that the flame caused by glycol often appears blue.
There are many scenarios where glycol could ignite, such as a car crash or a broken plug inside your vehicle. In most of these cases, there will be a pre-existing coolant leak that exposes glycol to a hot surface. This is why it’s crucial to bring your car to a mechanic if you suspect there’s a coolant leak.
If you’d like to learn more about the mechanics of engines and heat transfer, we recommend taking a peek at this detailed VEHQ post: Are Car Engines Supposed To Get Hot?
Can A Coolant Leak Cause A Fire?
Coolant leaks can cause a fire if they’re exposed to flames, high heat, or electrical sparks. In fact, a recent case study out of South Korea recently confirmed coolant leaks could be a primary cause of a car fire.
Of course, it takes longer for coolant to reach its flashpoint versus chemicals like gasoline, but that doesn’t mean it can’t cause a fire. For your safety, please call your mechanic the moment you notice a coolant leak.
What Is The Flashpoint Of Antifreeze?
A “flashpoint” refers to the minimum temperature required to cause a liquid to ignite and give off a vapor. In the case of antifreeze, the official flashpoint is between 230° F and 270° F. For comparison, the flashpoint on gasoline is only -40° F. Diesel, however, has a flashpoint of 120° F.
If you're interested in learning more about diesel vehicles, check out our post Should I Buy A Disel Car? [Pros And Cons].
How To Safely Check For And Prevent Coolant Leaks
Since coolant is a flammable substance, it’s imperative you know the signs of a coolant leak. You should also know how to check your coolant levels safely at home. In these final paragraphs, we’ll go over essential skills for checking and preventing engine coolant problems.
Can You Check Coolant When It’s Hot?
You should never check coolant levels when your car is hot. Even mechanics don’t even recommend checking coolant when your vehicle is warm.
The main reason mechanics are so strict on this rule has to do with safety. When your car is warm, the coolant fluid will be scorching. You will risk getting a severe burn if you take off the coolant cap shortly after turning your car off.
If you want to take a peek at your car’s coolant, then you should let your vehicle sit for at least six hours in your garage. Better yet, let your car rest overnight and check the coolant first thing in the morning.
Most often, manufacturers make it easy to spot the coolant cap by coloring it bright yellow. The reservoir should also be easy to see due to its semi-transparent appearance. You should notice a “full line” on the outside of your car’s reservoir to help judge how much coolant is in the container. If you’re having trouble spotting these units, please refer to your car manufacturer’s manual.
Can You Add Coolant When Your Car Is Hot?
Never add coolant to a hot car. Not only could this result in nasty skin burns, but it could also cause damage to your engine or cooling system. When you add cold antifreeze to a warm engine, it could “shock” your cooling system, thus increasing the risk of leaks and damage.
Allow your car to sit for a minimum of six hours before adding coolant. If you have specific questions about adding coolant to your car model, refer to your owner’s manual.
There are many coolant brands available online, but be sure to find the one that’s approved for your car model.
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How Often Should You Check Your Car’s Coolant?
There’s no precise timeframe for checking your car’s coolant, but a good rule of thumb is to check twice per year. If possible, schedule these inspections one month before the start of summer and winter.
If you’re driving a vehicle that does a lot of heavy-duty work, you might want to check your car’s coolant more often. For instance, people who drive trucks that tow a lot should check coolant levels roughly once per month. When in doubt, see what your car manufacturer has to say about engine coolant checks.
How Often Should You Change Your Car’s Coolant?
Like checking your engine coolant, there’s no standard timeframe for flushing car coolant. Some car companies say you should flush coolant every 30,000 miles while others recommend every 120,000 miles.
If possible, you should have your coolant checked every 50,000 miles. Your mechanic will run a few tests to determine whether it’s worthwhile for you to invest in a coolant flush. Typically, a coolant flush service costs about $100 – $150.
How Can You Prevent A Coolant Leak?
Other than using the maintenance strategies listed above, there’s not much you can do to prevent a coolant leak. Indeed, the best thing drivers can do is learn the warning signs of coolant leaks. The faster you can detect coolant leakage, the better chance a mechanic can quickly and safely patch up your problem.
A few common warning signs of a coolant leak include the following:
- The temperature gauge is above average.
- You smell a sweet odor.
- Your dashboard’s “Low Coolant Light” flashes.
- There are problems with your car’s internal heating system.
- You frequently notice steam or overheating.
The moment you suspect there’s a coolant leak, you should get in touch with a trusted mechanic. Driving with low coolant is a significant safety concern and could cause severe damage to your car’s engine.
If you want to learn more about how a coolant leak could cause overheating, check out our article discussing What Makes A Car Overheat.
How Much Does A Coolant Leak Repair Cost?
There are many potential reasons for a coolant leak, so it isn’t easy to give an accurate price estimate for a repair. However, the earlier you spot your coolant leak, the less likely it will do serious damage to your engine—and your wallet!
If the issue is simply a radiator hose leak, most mechanics won’t charge over $70 for a repair. However, if you have a blown head gasket, then it could be anywhere from $1,000 – $2,000 for a repair.
As you could see, it pays to get a coolant leak checked ASAP.
Even though coolant has a relatively high flashpoint, that doesn’t mean it can’t cause a fire. If you ever suspect your car has a coolant leak, you must bring it to a trusted mechanic ASAP. If left unchecked, a coolant leak could put you in harm’s way.