A good mechanic can diagnose problems without ever lifting the hood. Instead of just offending your nostrils, car smells serve as a helpful tool to determine the source of the trouble, from mildew in the air conditioner, to clogs in your catalytic converter, to a lead foot on the clutch.
Properly diagnosing a bothersome car smell may save a trip to the mechanic, or at least expedite the repair. A basic examination may uncover easy fixes: a gas cap left off, cracks in the tailpipe, or oil leaks. If everything is in place, however, the important thing is to identify what triggers the smell. Some smells only appear after applying the brakes, turning on the air conditioning, changing gears, or simply letting the car sit inactive for a long period of time.
Some car smells are particularly common, as are their triggers. Cars may smell of maple syrup, after the engine has been recently warmed up or shut off. The stench of old socks may emanate from the heater or air conditioner. The car may continually reek of sulfur, or of raw gasoline. Running the engine may evoke the smell of rotten eggs. The smell of burning paper may be constant, particularly while changing gears. The odor of hot oil may occur whenever the engine heats up, and a whiff of burning carpet may accompany the use of the brakes. Keep a nose out both for the smell of sickly sweet medicine, as well as the unmistakable odor of burning rubber.
Coolant contains ethylene glycol, which smells like maple syrup as it leaks from radiators or intake manifolds. That old gym sock smell can stem from mildew growing in the heating or A/C. Gear oil smells hideously like brimstone (sulfur), and can leak from differentials, manual transmissions, and 4by 4 transfer cases. Following the smell of gasoline or hot oil usually leads to the leak. A stench of rotten eggs - hydrogen sulfide - can be a bad sign for an old catalytic converter. A sniff of burning paper may point to the clutch, as friction burns the paper facing. The smell of burnt carpet, on the other hand, is probably thanks to overheated brake pads. Burnt rubber may trace back to a bad belt, or maybe a hose hanging too close to a hot engine. And leaking brake oil can evoke bad memories of oily, alcohol-based children's medicine.
Regular vehicle upkeep can help prevent many of these odors from happening. Mildew buildup should clear out after turning the fans on full-blast, and letting them run. Meanwhile, inhaling the aroma of overused brake pads might be taken as a sign to change one's driving habits. More severe problems - a failing catalytic converter, or a bad heater core - may require professional attention. But non-mechanical car odors - the persistent scent of a tuna fish dinner, forgotten in the sun - may simply require a liberal use of shampoo. Some home remedies, like pans of cat litter or open bags of charcoal left in the car, may also serve to absorb many persistent odors.
Many car smells can become dangerous for your body as well as your car. Gas leaks, for example, are a fire hazard waiting to happen. Leaking coolant can prove a tasty but deadly treat for a luckless pet. Mildew in the air conditioning can lead to the inhalation of some nasty bugs into the lungs. And in 2006, the Michigan-based Ecology Center revealed the famous "new car smell" as a witch's brew of toxic chemicals, which were built into the vehicle's plastic parts. Auto companies have since attempted to include 'safe' plastics in the manufacturing process.
