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6 Smells That Can Be Warning Signs When Buying a Used Car

Finding the used car of your dreams — or simply tracking down reliable wheels for your daily commute — involves patience, lots of tire-kicking, and some detective work. Beyond the obvious visual signs of disrepair or poor maintenance, certain car smells can be warning signs of ongoing or potential problems.

Seasoned car shoppers should be aware of clues from specific car odors that may signal trouble. Look — and sniff — carefully when test-driving your new-to-you vehicle. Continue reading to help you learn what that car smell is.

1. Oil

Oil is the lifeblood of your engine, and it needs to stay inside of it. Smelling hot or burnt oil could mean oil is leaking onto the exhaust manifold or another hot portion of the driveline. At the same time, an unscrupulous seller might wipe down leaking areas. So also beware of clean, shiny parts on the engine or drivetrain. Check for oily patches on the ground where the vehicle parks to verify a leak. If you smell burnt odors from the engine bay, look carefully for smoke around the running engine and beneath the vehicle.

2. Burnt Rubber

The stench of burning rubber could mean a slipping drive belt or a loose hose rubbing against rotating accessory drive-belt pulleys. Check the tension of exposed belts and look for uneven wear, cracks, or missing chunks of the material. Look for a vacuum hose resting on the hot engine block in older cars. Keep safety in mind, and ensure the engine has cooled off before checking hoses or other components under the hood.

3. Gasoline

A raw gasoline scent might be due to a bad gas line or faulty fuel injector. In some cases, it could be from a leaky gas tank. These possibilities are not minor issues that can be ignored or addressed with a quick fix. The smell of gas fumes indicates a potential ignition hazard, so an immediate repair is necessary. If you’ve ever witnessed a single car on fire on the side of the highway — or its charred remains — the culprit was likely a fuel leak.

4. Syrup

A sweet or maple syrup-like aroma is probably from antifreeze. The smell indicates the car is leaking engine coolant, the heater core has failed, or another component of the car’s cooling system is compromised. The scent is usually faint at first before getting progressively worse. Look for liquid in the parking area and check the coolant level after the first whiff of syrup. Ensure the engine is cool before removing the radiator cap. Depending on the severity and location of the leak, some products can temporarily lessen or plug the leak. However, they won’t permanently solve the problem.

5. Melting Plastic

Another stench from a troublesome used truck, car, or SUV resembles melting or burning plastic. The intense smell could be an indication of brake problems. Check for leaks at the master cylinder and pinpoint the source of the odor. Address this issue quickly and firmly with the seller. Insist on checking the brakes immediately because it could be a safety issue that ends up being a very costly repair.

6. Rotten Eggs

There is no mistaking the sulphury, foul odor of rotten eggs. This putrid smell might represent something as minor as a bad tank of fuel, a fuel filter, or a failing fuel pressure sensor. However, it could be a more severe problem if the catalytic converter is not converting hydrogen-sulfide exhaust to sulfur dioxide as it should. Replacing a converter can turn a cheap used car into an expensive one. Expect to pay about $3,000 for a new catalytic converter, including labor.

Be Aware and Inspect

During your test drive or inspection, you might encounter other car smells. Detecting an unpleasant scent is not an automatic deal breaker. Some vehicle odors don’t predict mechanical issues at all. Face it, funky smells might exist because of the car owner’s poor hygiene, and what lingers can be removed using odor elimination products, a thorough cleaning, or professional car detailing.

Talk to a trusted mechanic and determine the source of any odor and how much it will cost to fix the cause. Odd smells or not, we recommend you take any prospective vehicle to a certified mechanic for inspection before deciding to buy.

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Editor’s Note: This article has been updated for accuracy since it was originally published.


How can I get smoke smell out of a car?

Getting rid of smoke smell from a car requires deep cleaning the carpet, fabric floor mats, and cloth upholstery before using a dedicated smoke removal product to help deal with unreachable areas such as HVAC vents and headliner foam.

Why does my car smell like gas?

There are several reasons why you might smell gas in your car. If the fumes seem to come from the engine compartment, something could be wrong with the fuel injectors. If the smell of fumes comes from elsewhere, the cause might be less severe — a missing or loose gas cap.

What is the rotten egg smell in my car?

The rotten egg smell of sulfur in your car could be from a faulty catalytic converter. Another, and less severe, possibility is a faulty fuel pressure sensor.

Chris Hardesty
Chris Hardesty
Chris Hardesty is an author specializing in general car tips and electric vehicles. He spent more than 25 years in newspapers, including leading editorial research efforts at The News & Observer in North Carolina, The Mercury News in California, and Newsday in New York. After that, he was an online news editor at The Wall Street Journal before moving to the Atlanta area. He didn’t have a... Read More about Chris Hardesty

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