Whether you’re test-driving a used car before a potential purchase or driving a car you’ve happily owned for years, your senses can often detect fairly easily if something isn’t quite right.
Know the warning signs, and your sense of touch can feel and detect the dull vibrations caused by a worn CV axle, or the tugging and pulling in your vehicle’s steering characteristic of alignment trouble. Your sense of hearing can help alert you if the engine’s running poorly, or if a wheel bearing is roaring away beneath the vehicle, putting safety and efficiency at risk.
Obviously, your sense of sight plays an important role in automotive troubleshooting, too.
Not your sense of taste though. We don’t recommending tasting your car, or any of the fluids used to make it work.
So, that leaves just one — your sense of smell.
Never underestimate your olfactory facilities as a potential diagnostic tool and means of sniffing out potential trouble with your car (or that used car you’re considering buying).
Below, we’ll look at a few smells that could spell serious trouble. Each of these is a good reason to have your vehicle inspected by a professional, or to proceed with caution on that used car purchase.
Sniff For This: Dirty socks, smelly gym-bag, hot vomit, nasty mildew towels
What’s That Smell: Some smells are just plain gross, and though many things can stink up an otherwise good car, a few of these more severe smells can indicate some major problems.
If you smell something that resembles vomit, mould, filthy shoes, or the mildew-infested towels you forgot to take out of the washing machine for 4 days, there could be serious trouble lurking.
Smells like these are commonly associated with a buildup of mould and mildew somewhere inside of your vehicle, especially if all other cleaning measures fail to remove the odor.
In modern cars, there are two common culprits for smells like this.
The first is a water leak, something typically caused by a problem with the vehicle’s sunroof drainage system, a badly-sealed windshield, improperly-sealed roof rails, or an issue with missing or damaged weather sealing on an exterior door, brake light, or even the rear window of your pickup truck. These leaks tend to cause a buildup of moisture in the vehicle’s carpeting and the carpet padding beneath. Eventually, mould and mildew form, followed by rust and corrosion. Before long, the vehicle’s carpet pad becomes a cesspool of smelly microorganisms.
Damp carpeting can also be caused by a problem with your vehicle’s air conditioner, leading to a similar result. To best sniff out this smell on a used car test-drive, take careful note of the smell of the car’s interior when first getting on board, after ensuring all windows are closed. Does the car smell dry and clean? Or dank and mouldy, possibly with an attempt to mask the odor with a deodorizer?
The second culprit is a buildup of mould and mildew inside of your vehicle’s climate control system ducting and hardware. The parts of your car’s heater and air conditioner are a great place for mould and mildew to take up residence, which becomes more likely in hot and humid conditions that see those parts stay damper, for longer. A mould and mildew infestation within your climate control system can be detrimental to your health, and in some cases, the odor is unbearable.
Floor mat cleaning Photo by Getty
Clear the Air:
If your car (or the car you’re considering) car has a water leak, it’ll typically have moisture, rust, or standing water in the spare tire well, as well as damp or soggy carpeting, especially at the vehicle firewall and outer corners of the cabin.
Be on the lookout. Some water leaks have simple solutions, like clearing the sunroof drain inlets. Others can require costly and frustrating repairs, and thousands of dollars in parts.
If you suspect your climate control system has been taken over by mould and mildew, talk to your service provider about cleaning and sanitizing solutions that may be available.
In some vehicles, the best course of action is to have the climate control system ducting professionally cleaned and sanitized, followed by a software update that alters climate control system operation to help mitigate mould and mildew formation by running the climate control fan a few extra moments after a long drive in humid conditions, helping to dry certain components and slowing mould growth. Some drivers in humid climates perform this step manually after driving on humid days, with good results at keeping mould and mildew at bay.
Refilling engine oil Photo by Getty
Sniff For This: A strong gasoline odor, especially when checking the engine oil
What’s That Smell: Gasoline fuels our engines, and if our engines and associated parts are working properly, you should almost never smell it. Automakers go to great lengths to capture and recycle gasoline vapors from our fuel tanks and engines, and to prevent gasoline vapors from entering the atmosphere at large. In fact, other than when filling up our tanks, there’s virtually no good reason to smell a strong fuel odor from your car (or the car you’re considering for purchase).
Do you smell the odd whiff of unburnt gasoline from your car? Is it stronger when you open the hood? Though various fuel leaks and other problems can result in worrisome fuel odors, these are relatively rare in newer vehicles.
Still, some cars require an extra check with your nose—just to be safe.
Some owners of earlier-build, recent Honda vehicles like the Civic and CR-V with the 1.5-litre turbocharged four-cylinder engine have reported various engine problems, some of which include a strong fuel odor as a telltale symptom. Most have not.
If the engine is suffering from a problem called oil dilution, unburnt fuel could be entering the vehicle’s engine oil supply, which is bad news. A side-effect of this problem is a strong fuel odor that’s often stronger when the vehicle’s hood is open, and stronger still if its engine oil dipstick is removed.
Clear the Air:
When checking the oil level in your car (or a used car you’re considering) it should smell like warm and silky engine oil, not fresh gasoline. If you detect a strong gasoline odor from the dipstick when checking the oil level, especially on a Honda 1.5L turbo engine, it could be a sign of potentially serious trouble.
Have the vehicle seen by a professional for an assessment.
Auto mechanic holding used car pressure plate, clutch disc and release bearing in front of the vehicle engine Photo by Getty
Sniff For This: Gunpowder, freshly popped caps from a toy gun, sulphur stench rotten eggs
What’s That Smell: Chances are you know what gunpowder smells like — especially if you’re a hunter, or if you’ve ever fired a toy cap-gun. Chances are you’re also familiar with the sharp and sulphuric reek of rotten eggs.
Imagine a smell that sits somewhere on the spectrum between those two, and be on the lookout for it when driving a car with a manual transmission.
The smell described above is a common sign of a clutch that’s being overworked, overheated, or slipping. Almost nothing else in a car can create this specific smell, and if you detect it, it can be a strong indication of clutch problems that are happening now, or are about to.
Note that this smell can also be a sign that you haven’t quite mastered the use of a manual transmission, too.
Manual pedalbox Photo by Getty
Clear the Air:
In addition to the nasty smell of rotten eggs and spent caps, signs of a badly worn clutch can include unwanted scraping and grinding sounds as you release the clutch in neutral, rough or noisy engagement of the clutch while in gear, and a tendency for the clutch to slip when full throttle is applied in a low gear while driving up a steep hill.
Clutch replacement can be expensive, so take this smell seriously.
Green coolant leaking onto the engine. Photo by Getty
Sniff For This: Crème brulee, toasted sugar, maple syrup
What’s That Smell: If you’re at the wheel and a warm, wet and sweet smell enters your nostrils, it could be that you’re driving near a bakery or a sugar bush.
It could also mean that your car is suffering from a coolant leak, a cracked heater core, a blown water pump, or a failed head gasket, with the likelihood of engine failure increasing with each passing moment.
It’s important to take smells like these seriously. Hopefully, that warm, sweet smell is just some nearby maple syrup — but it could also be a sign of serious trouble that could turn your engine into soup.
Engine coolant generally has a sweet, hot, and sugary smell. After your engine has been running for a few minutes, this coolant reaches a steaming-hot temperature, meaning that a leak is fairly easy to sniff out — especially if the engine is nice and hot.
A blown radiator, rad hose, water pump, or fitting can result in a leak of hot engine coolant, accompanied by that smell. A failed head gasket can have the same effect. If you pick up the telltale scent of hot engine coolant, be on high alert, and pay attention to your engine temperature gauge, or instrument cluster, since overheating is likely.
A cracked or leaking heater core can cause a similar leak of hot engine coolant, and a similar smell — though typically stronger, as this leak can allow hot coolant directly into the vehicle’s cabin.
Well, this isn’t good. But if you know where it’s coming from, dealing with a leak shouldn’t be too much of a hassle. Photo by Supplied /iStock.com via Getty Images
Clear the Air:
If you smell something sweet, and especially if you smell something sweet a moment or two before your engine overheats, exit the roadway immediately, check your owner’s manual for further instructions, and make plans to call a tow truck.
In this situation, a thick and heavy plume of bright white vapor may be visible in your rearview mirror. If you notice it, the source is likely your car’s tailpipe, and this is a sure sign of head gasket or cylinder head failure, which is more likely if the engine is driven in an overheated state.
Hopefully that’s not the case, but remember that driving an overheated engine can cause fatal damage that isn’t necessarily covered by your new car warranty.
Even if there’s no overheating, take the presence of a hot coolant smell seriously and have a technician investigate. Small coolant system problems can typically be repaired inexpensively, before they become more serious.
Keyword: What's that smell? How to sniff out vehicle trouble before it costs you money