A burning smell from a car usually points to oil leaking onto the hot exhaust, overheating brakes or clutch, coolant leaking onto hot parts, an electrical short, or overheated transmission fluid. The type of smell helps narrow it down, and some causes, such as an electrical burning smell or smoke from under the hood, mean you should stop and switch off the engine right away.
What the smell tells you
| Smell | Likely cause |
|---|---|
| Burning oil | Oil leaking onto the exhaust manifold, often from a valve cover gasket or oil filter |
| Sweet, syrupy | Coolant leaking onto hot parts, or a heater core leak |
| Acrid, burnt paper or friction smell | A slipping or overheated clutch, or dragging brakes |
| Burnt plastic or rubber | An electrical short, melting wiring, or a loose hose or belt touching something hot |
| Sharp, burnt smell from transmission fluid | Overheated automatic transmission fluid |
| Rotten eggs | A struggling catalytic converter, often from a rich mixture |
Burning oil smell
The most common cause. A leaking valve cover gasket, oil pan gasket or a loose oil filter drips oil onto the exhaust, where it smokes and smells. Check under the car and around the exhaust manifold for wet, dark residue. If you also see blue smoke from the tailpipe, the engine may be burning oil internally; see exhaust smoke colors.
Sweet burning smell
Coolant has a sweet smell. Leaks onto hot engine parts or a leaking heater core produce it, and an engine losing coolant can overheat; see coolant leak and engine overheating.
Clutch and brake smells
A slipping clutch smells sharp and acrid, especially after a steep hill start or heavy towing. If it smells after normal driving and the engine revs rise without matching acceleration, the clutch is likely worn; see signs of a bad clutch. Brakes that drag or overheat on long descents produce a similar smell from the wheels.
Burnt transmission fluid
Automatic transmission fluid that overheats, from towing, low fluid or slipping, smells sharp and burnt and darkens quickly. Check the level and color; see transmission fluid color and transmission fluid temperature.
Burning smell after an oil change or repair
Oil spilled on the exhaust during an oil change, or residue left after a repair, can smell for a day or two as it burns off. If the smell continues or you see smoke, look for an active leak.
Electrical burning smell
Burnt plastic or insulation smells can mean a short circuit. Pull over, switch off the engine and look for smoke. Do not keep driving with an electrical burning smell.
More guides: bad alternator symptoms · transmission overheating · car smells like gas · exhaust leak symptoms · valve cover gasket leak.
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