When someone has car trouble on TV or in a movie, the scene typically shows the character pulled over on the side of the road, standing in front of their vehicle’s open hood, watching smoke billow out. Regardless what viewers know about cars, that dramatic visual suggests that the car has overheated.
But just because people are aware of the possibility of their car overheating doesn’t mean they know how to tell if it’s happening or how to handle the situation. That’s why Lifehacker enlisted the help of some expert mechanics to walk us through the signs that your car is overheating, and what you should do next.
The signs a car is overheating
When we talk about a car overheating, we’re really referring to the engine overheating. The good news is that your car isn’t going to go from everything running as it should, to smoke (or more likely steam) coming out from under the hood in an instant. First, there will be clues that something is wrong. “When you’ve been around cars as long as I have, you get familiar with the signs of an engine running hot,” says Robert Walden, a longtime mechanic and founder of Vehicle Freak.
But before we get into those, we should point out that these signs are based on some of the most common scenarios and is not an exhaustive list. Plus, as John Lin, a mechanic and the owner of JB Motor Works points out, “different car makes and models may have other specific needs or symptoms.”
Generally speaking, some common signs that a vehicle is overheating include:
You smell something sweet
If your car is beginning to overheat, you may notice a sweet, warm smell, or see a vapor. “This is antifreeze, and will likely be the first symptom that a closer look may be required,” Andy Saari, A.S.E. certified master technician and founder of Nexedge Technician, says. When a car is running properly, we’re not able to smell its various fluids while driving, because they’re busy keeping the car cool, Lin explains. “So, a smell [of fluids] could indicate [that] they’re leaking onto hot parts of the engine,” he says.
A high reading on the temperature gauge
Most traditional temperature gauges don’t include numbers, but instead represent a range from cold to hot (C to H), with the hot end of the scale usually shown in red. “The temperature gauge pushing into the red zone is a dead giveaway—time to back off and give that baby some breathing room,” says Walden.
A dashboard warning light or indicator
Temperature gauges, like the ones described above, are no longer standard in every vehicle, Saari points out. Instead, your check engine or temperature warning light might light up or start to flash, according to Lin. Some vehicles also have a dedicated low-coolant light; if it turns on or flashes, it’s a sign that your car is in danger of overheating.
Strange sounds
According to Walden, if you hear knocking or rattling noises while driving, it probably means that the parts in your car’s engine are in desperate need of oil’s lubrication.
You smell something burning
The scent of an overheating engine isn’t always sweet. According to Michael Dominguez, a certified master mechanic and the founder of Car Fixer Guide, you may also get a whiff of “an unusual smell, like burning rubber or hot oil.” When you notice either of those odors—or the smell of burning plastic—”that’s hot components in the engine bay reaching their limit,” Walden explains.
Weak or sputtering engine
If you notice your engine sputtering and lacking power when you hit the gas, it could be a sign of a problem with your car that’s causing it to overheat, says Walden.
The hood is hot
If you’ve pull over and gotten out of the car, carefully touch the hood. “If the hood feels like a frying pan, with heat wafting up in visible waves, trouble’s brewing under there,” says Walden.
Steam coming from under the hood
Lastly, if you notice what Walden describes as “clouds of steam billowing out from under the hood,” you need to take action as soon as possible.
What to do if your car is overheating
If you recognize one or more signs indicating that your car is likely overheating, it’s important to act immediately. “Understanding and responding correctly to overheating can prevent significant damage to your vehicle and ensure your safety on the road,” Dominguez says. Here’s what to do:
Pull over as soon as you can
Once you suspect that your car is overheating, pull over to the side of the road as soon as you have the opportunity to do so safely, Dominguez, Lin, and Walden all point out. Then “shut off the engine immediately, before it boils over or gets damaged,” says Walden, but “don’t even think about opening the hood till it’s cooled down.”
Turn off the AC and turn on the heat
For a variety of reasons, it’s not always possible to pull over immediately upon realizing your car might be overheating. So while you’re looking for somewhere to stop, Lin recommends switching off your air conditioning and turning on your heat. In fact, Saari and Walden advise cracking the heat up to the highest setting. “This can help draw heat away from the engine,” Dominguez explains. “However, this is a temporary measure and shouldn’t replace stopping and addressing the issue.”
Adjust your driving and route
While you’re looking for somewhere safe to pull over, Lin says that “driving a bit slower and avoiding steep inclines can help.”
Your car might self-adjust
As technology advances, cars getting better at self-regulating—including when it comes to engine temperature. “Modern vehicles have a self-protection mode built into the computer that helps protect the engine in the event it begins to overheat,” Saari explains. “It usually involves shutting down cylinders to reduce engine temperature, and power.”
When this happens, the car may eventually shut down completely, says Saari. “The engine fan will also likely sound much louder than normal, because it will be running at its highest speed,” he adds.
What to keep in your car in case it overheats
Whether you already stock your vehicle with emergency supplies or you’re putting your first kit together, here’s what the experts we interviewed recommend keeping in your car to ensure you’re prepared if it ends up overheating:
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Basic set of tools, like this one from Stalwart ($14.71)
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A gallon of prediluted coolant, like Valvoline Multi-Vehicle 50/50 Prediluted Ready-to-Use Antifreeze/Coolant ($20.17)
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Distilled water
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An engine coolant additive, like Red Line Water Wetter Super Coolant ($11.89)
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LED flashlight or headlamp, like this one from Energizer ($10.40 for two), which is also water resistant
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Owner’s manual
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First aid kit, like this one from YIDERBO ($12.91)
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Extra phone charger
If you’re starting from scratch, you may want to purchase a complete car emergency kit. Saari recommends the Everlit Roadside Emergency Kit ($64.95). “It has a warning triangle and a blanket, along with other items that may be helpful in different situations,” he says.
