When an unusual smell emanates from your vehicle, your first impulse might be to check under the seat for an old fast food bag. If the culprit isn’t in the interior of your car, chances are it’s your engine. Smells generated by a vehicle's engine can point to potential trouble ahead. Here are six smells to be wary of and a list of what mechanical issues trigger them.

Rotten Eggs or Sulfur

If a smell is similar to rotten eggs, this could indicate that your catalytic converter may not be properly processing hydrogen sulfide in the exhaust. Take your car to a mechanic as soon as possible.

Maple Syrup

If your engine has been running for a few minutes and you start to smell something sweet, coolant containing ethylene glycol could be leaking from the radiator, cylinder head or a failed intake manifold gasket. If the smell is strongest inside the car, this is could indicate a problem with the heater core. In both cases, you’ll need to have a mechanic look into the issue.

Burnt Paper

The smell of burnt paper while driving, especially when changing gears, might be a sign that the clutch facing is burning off as the clutch slips. This can happen if the driver is “riding” the clutch, stepping too frequently on the pedal, which causes significant friction. This friction creates enough heat to actually burn the paper-based clutch facings, which can cause the whole clutch to fail.

Burnt Oil

Smelling burnt oil? First, check the oil dipstick. You might be running out of engine oil or your engine could be overheating. If neither is the case, look for oil leaking onto the engine block or exhaust manifold. Next, check your transmission fluid. If it’s low, it could be burning in the transmission because the gears aren’t properly lubricated and are overheating. Also be sure that you’re using the correct type of engine oil for your vehicle. Use the Cenex® Equipment Lookup feature to help you find which lubricants are recommended for your car.

Musty Basement

If you turn on the heater or air conditioner and it smells like a musty basement, you could have mildew growing inside the AC evaporator. Turn off the AC and drive with the fan on high to dry the system out.

Burnt Carpet

A burnt carpet smell, especially after extensive use of the brakes, could mean your vehicle’s brake pads are overheated, or you left the hand brake on. When this happens, take your vehicle to a mechanic to replace the worn brake pads.  

Cars may sometimes seem like a mystery, but the occasional whiff can help you diagnose common vehicle problems before they become major issues. 

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