There's rarely a single cause for any given car fire, even if an investigator can trace all the way back to the incident that sparked the blaze. It's more likely that there was a combination of causes: human causes, mechanical causes, and chemical causes, and they all worked together to create an incredibly dangerous situation. In other words, once a vehicle's on fire, any number of additional factors can (and will) complicate things. Knowing what those factors are can potentially help a car owner avoid a dangerous situation, but there are no guarantees. And the most important thing to remember is that once a vehicle is ablaze, it really doesn't matter what caused it -- your car is on fire. Don't worry about whether the engine was overheating or what fluid you might have spilled (although that information might be useful later, for insurance purposes or to help an auto manufacturer fix a potential flaw). Right now, it's imperative that you get out fast and get as far away from the car as possible. A small car fire isn't going to stay small for long, and any combination of the initial causes (or complications) we'll discuss in this article will quickly make the situation much, much worse. The National Fire Protection Association (NFPA) says that vehicle fires account for about 20 percent of all reported fires, so it's worth knowing how to reduce some of the risk in your own car or truck [source: Chandler Law Group].
A design flaw in a vehicle usually isn't going to cause a car fire on its own, because there's no on/off switch for lighting a vehicle ablaze. Design flaws, however, can make conditions really ripe for a fire, and sometimes even create conditions in which an eventual fire is inevitable. Usually, the manufacturers catch on to these situations before incidents become widespread. They issue recalls to get the dangerous cars off the street and fix the problems, because no carmaker wants to be known for combusting its customers. Like all automobile fires, a design flaw is only the first step leading to a blaze. Not all design flaws result in a fire, but any number of problems can make a fire a lot more likely. Though some recent incidents will be used as specific examples on the following pages, it's worth noting that every major auto manufacturer (and plenty of the smaller ones, too) has recalled a vehicle due to a fire hazard [source: Chandler Law Group].
Human error probably isn't going to be the direct cause of a fire in your vehicle -- after all, being lazy isn't quite the same as striking a match and igniting a wick that goes into the gas tank. But if you're sloppy about maintenance, your car is going to be a lot more dangerous, in general, and the increased likelihood of a car fire is just part of the greater risks you're taking. It's true, forgetting or neglecting to properly take care of your car can indirectly lead to a vicious fire. That's because if you let broken parts, leaky seals, or faulty wiring go without repairs, it'll make your car a lot more hospitable to the conditions that cause a fire. An engine with a bad gasket is more likely to drip hazardous (and flammable) fluids. Frayed wiring is more likely to spark and make contact with flammable materials. Isn't it better to know if your car is a potential deathtrap? Just pop the hood every now and then and take a cursory look around.
Depending on the impact site, a car crash can even spark a car fire. Most vehicles' crumple zones are designed pretty well, so the sheet metal absorbs the force of a blow and protects internal, dangerous spots like the engine, the battery and even the gas tank. But really, there's not actually that much of a barrier there, so a hard enough hit is likely to cause fluid leaks and spillage, as well as heat and smoke. And, as we know, high heat and spilled fluids create perfect conditions for a fire. Since it's hard for occupants of a crashed vehicle to see the extent of the damage while they're still inside, the threat of a fire might not be immediately apparent; however, it's always best to get away from a damaged car as soon as possible. Consider yourself lucky if you're not trapped inside a crashed vehicle -- even if it does go up in flames, at least you're a safe distance away.
Arson -- the criminal act of setting a fire. Now, why would anyone deliberately set a car on fire, anyway? It could be to cover up a theft, or to cover up the evidence of another crime. It could be old fashioned vandalism, too, wrecking something just for the sake of wrecking it. Or it could be insurance fraud. And there are probably several more reasons, but that's best left to the criminal masterminds. It's worth noting that it's pretty easy to set a car on fire -- perhaps doing it without being detected is a challenge, but actually igniting a car blaze is simple. An arsonist can use any combination of catalysts, causes on this list (and more) to start the fire -- and a skilled auto arsonist can sometimes get away with it, too. After all, the physical evidence is a smoldering mess. We aren't advocating this by any means, but we are saying that an arsonist is yet another reason your car might be ablaze.
Not long after the Tesla Model S was awarded the unofficial title of "the safest car ever" by the media (and by Tesla Motors), a Tesla Model S caught fire in the fall of 2013. That's never good, of course, but for Tesla, it was especially bad. The company had implied numerous times that its fully electric Model S was all but immune to the battery-related problems that have plagued hybrid cars and EVs of the past. Alas, a Model S traveling at high speeds hit a piece of debris that punctured the car's battery, and the battery behaved like any other battery would: it ignited.
Throughout 2011 and 2012, the Chevy Volt made headlines when a bunch of test vehicles caught fire during impact testing. Federal regulators determined that in most of these cases, leaking coolant interacted with the damaged batteries to spark the blaze, and General Motors was able to come up with a fix that satisfied government safety officials. Concerns about hybrid and electric batteries go way back, though, and there are new potential risks with each new design. It might be a while before the safety concerns from these high profile incidents fade from the public consciousness.
Overheating catalytic converters are a fire risk that's often overlooked, but think about it: One of the consistently hottest parts of your car runs the entire length of the vehicle -- the exhaust system. Catalytic converters usually overheat because they are working too hard to burn off more exhaust pollutants than they're designed to process. In other words, if the car's engine isn't operating efficiently (due to worn spark plugs or any number of other adverse conditions), it doesn't burn the fuel properly, and a lot of extra stuff ends up in the exhaust system. The cat then has to work extra hard to do its job, which makes it even hotter than usual. An overworked (or clogged) catalytic converter can easily go from its normal operating temperature range of about 1,200 to 1,600 degrees Fahrenheit (648.9 to 871.1 degrees Celsius) to up over 2,000 degrees Fahrenheit (1,093.3 degrees Celsius). This causes long-term damage not only to the cat itself, but to the car's surrounding parts. The car's designed to withstand the cat's normal temps, but it can't consistently cope with temperatures several hundred degrees higher. If the catalytic converter gets hot enough, it could ignite the cabin insulation and carpeting right through the heat shields and metal floor pan.
An engine that overheats and causes a car to catch on fire is an especially good example of how one problem can lead to another. A car's engine probably won't overheat enough to simply burst into flames all on its own. But what can happen (and pretty easily, by the way), is an engine can overheat and make the internal fluids, like oil and coolant, rise to dangerous temperatures and begin to spill out of their designated areas of circulation. When that happens, they drip, drizzle and spurt throughout the engine bay and onto the exhaust system, landing on other hot parts, where they can easily ignite and spread.
In some cases, like the late-2012 recall of about 90,000 Ford cars equipped with a specific EcoBoost powertrain, an engine that overheats is sometimes a design flaw that's fixable with a software update -- modifying the car's computer to help keep engine temperatures at a safer (lower temperature) threshold. Generally, though, an overheating engine requires mechanical attention. There's often a leaky seal or gasket, or the radiator isn't working properly, or any number of other things. If your car's engine is constantly overheating ... well, that's not a symptom to ignore.
The average car or truck has a number of flammable and highly dangerous fluids under the hood: gasoline or diesel fuel, engine oil, transmission fluid, power steering fluid, brake fluid and even engine coolant. All of those fluids are circulating when the car is on, and all of them can catch fire pretty easily if their lines, hoses or reservoirs take a hit. So even though one of the car's vital liquids is unlikely to start spewing or dripping out of nowhere -- generally, something else has to go wrong first -- the fact that all of these fluids are flammable to begin with is a problem in and of itself. Combined with another aggravating factor, like a car crash or a failed part, the result could be a fire. Though such a blaze is most likely to start in the engine bay, where all of these dangerous liquids are concentrated, keep in mind that some of them, like fuel and brake fluid, are moved along the entire length of the car.
Electrical system failures take the second spot on the list because they're the second most common cause of car fires [source: Walters Forensic Engineering]. Car batteries are problematic, and not just the hybrid and all-electric vehicle battery pack types we've already discussed. A typical car's standard battery is capable of causing plenty of trouble. The battery's charging cycles can cause explosive hydrogen gas to build up in the engine bay, and the electrical current the battery provides (along with faulty or loose wiring) can produce sparks that can quickly ignite a fluid drip or leaked vapors. The electrical system's hazards aren't confined to the area under the hood, either. Electrical wiring runs throughout the entire car; through channels, into doors, under the carpet and through powered and heated seats, just to name a few places where a stray, unnoticed frayed wire could cause havoc.
Leaks in the fuel system are the most common cause of vehicle fires, so that's why they take the top spot on our list [source: Chandler Law Group]. As we've already seen, any number of complicating factors can cause a fuel leak, but they're tricky because fuel leaks can also arise on their own and with very little warning. A fuel system leak is really dangerous. We've already discussed that a lot of a car's fluids have corrosive, poisonous and flammable properties, but gasoline is among the worst. Gasoline at a temperature of just 45 degrees Fahrenheit (7.2 degrees Celsius) or above can quickly catch fire from a simple spark. It happens all the time in a running car, after all, but it's contained by the engine. And gasoline that reaches 495 degrees Fahrenheit (257.2 degrees Celsius) will ignite by itself. It's easy to see how fuel dripping onto hot metal and plastic parts can cause a fast-spreading fire. The best way to reduce chances of a fuel system fire is to make sure the car is properly maintained and to keep it out of the situations we've already described. And if you ever smell gas in or around your car, find and fix the leak immediately!
If your used car gets recalled, can your still get it fixed? Find out what to do if your used car gets recalled at HowStuffWorks.
Author's Note: Top 10 Causes of Car Fires
A lot of the facts about car fires seem like common sense. For example, most car fires start in the engine compartment, which shouldn't be any surprise to anyone who's ever popped the hood to have a look at what goes on in there. And if your car catches on fire, you should always try to get as far away as possible. (Instead of, say, standing around filming it, setting it to Weezer's "Say It Ain't So" and then posting it online. I saw this once in a video, back when I was a moderator on a Volkswagen forum and a well-known member's car mysteriously went up in flames. Honestly, that was all I could think about the entire time I was researching and writing this article). But maybe that's being too harsh. Vehicle fires are scary, and the movies and TV would have us all believe that any car that's on fire will immediately blow up. Just don't pull out your phone to check this list (or film the fire) until after you're a safe distance away.
- AA1Car.com. "Catalytic Converter." (Oct. 8, 2013) http://www.aa1car.com/library/converter.htm
- Chandler Law Group. "Common Causes of Car Fires." (Oct. 5, 2013) http://www.chandlerlawgroup.com/library/common-causes-of-car-fires.cfm
- Eisenstein, Paul A. "Ford finds software fix for engine fire problems." NBC News. Dec. 10, 2012. (Oct. 5, 2013) http://www.nbcnews.com/business/ford-finds-software-fix-engine-fire-problems-1C7529222
- Hirsch, Jerry. "Probe of Chevrolet Volt fires ends; safety regulators OK GM's fix." Los Angeles Times. Jan. 21, 2012. (Oct. 5, 2013) http://articles.latimes.com/2012/jan/21/business/la-fi-autos-volt-20120121
- Mobil 1. "Replacing Relays in Car Electrical Systems." (Oct. 8, 2013) http://www.mobiloil.com/USA-English/MotorOil/Car_Care/DIY/Replacing_Relays_in_Car_Electrical_Systems.aspx
- National Fire Protection Association. "Vehicles." May 2013. (Oct. 5, 2013) https://www.nfpa.org/safety-information/for-consumers/vehicles
- Panzarino, Matthew. "Elon Musk Details Cause of Tesla Model S Fire, Says It Would Have Been Worse With Gas." TechCrunch. Oct. 4, 2013. (Oct. 5, 2013) http://techcrunch.com/2013/10/04/elon-musk-details-cause-of-tesla-model-s-fire-says-would-have-been-worse-with-gas/
- Vlasic, Bill. "G.M. Recalls 475,000 Chevy Cruzes to Fix Engine Fire Hazard." The New York Times. June 22, 2012. (Oct. 5, 2013) http://www.nytimes.com/2012/06/23/automobiles/gm-recalls-475000-chevy-cruzes-to-fix-a-potential-engine-fire-hazard.html
- Walters Forensic Engineering. "Motor Vehicle Fires." (Oct. 5, 2013) http://www.waltersforensic.com/articles/fire_investigation/vol3-no1.htm