8 Car Smells That Could Signal a Problem

Cause: If you notice a whiff of rotten eggs while the engine is running, chances are there is something wrong with your catalytic converter. The gasoline contains traces of sulfur, which produces hydrogen sulfide in the exhaust gases. These exhaust gases are treated in the catalytic converter and converted to sulfur dioxide. If the catalytic converter fails, the sulfur can escape, producing a strong rotten eggs smell. Sometimes, this odor can also occur if the catalytic converter is overloaded or clogged due to a poorly running engine. This happens because of a failing fuel pressure sensor that allows too much fuel into the engine.

What To Do: If the catalytic converter is faulty, it needs to be replaced. If your car smells like rotten eggs and is accompanied by a check engine light on the dashboard, you should consult a mechanic. By detecting the problem early, you can save the high  cost of replacing a catalytic converter.

Cause: One of the most common reasons ‌your car smells like gas might be that you recently refueled your tank. Often, traces of gasoline can make their way into the vehicle if you accidentally spill a bit on your hands or clothes. However, this odor of gasoline eventually fades. If it doesn't, then check for  a gas leak in your fuel system. A simple way to detect a leak in your fuel system is to check for fuel puddles under the vehicle. A leaking fuel injector with a damaged O-ring or rubber seal can also allow fuel to escape from the combustion chamber. Other conditions that can lead to gas smells are leaking or cracked fuel lines, a punctured or degraded fuel tank, or a loose or missing fuel tank cap.

If you own an old car with a carburetor, the gas smell is normal and is usually caused by fuel boiling in the carburetor's float bowl (also known as after boiling). However, modern cars are equipped with an evaporative emissions control system that prevents the gas fumes from escaping. So if your car smells like gas, there could be a fault in the EVAP hose.

What To Do: If you smell gasoline, it is recommended to stop the car and check for torn or cracked fuel lines and puddles under the vehicle. It's necessary to seek mechanical assistance because gasoline is highly flammable and a leak can cause  fire.

Cause: If you smell exhaust fumes inside your cabin, it might be due to a leak in your car's exhaust system. This can happen because of a damaged muffler, a leaking exhaust manifold gasket, or a cracked exhaust pipe. As you drive, the exhaust gases can escape the system quickly and make their way into the cabin, giving an unpleasant odor. If the exhaust system is leaking, you will also hear hissing or loud sounds while driving. If the exhaust system is working fine, get the door seals checked and replaced if they are torn, warped, or broken.

What To Do: Exhaust fumes contain carbon monoxide and other harmful gases that are poisonous. If your car smells like exhaust, ‌drive with the windows open and head straight to the repair shop to get your vehicle checked. It is important to identify a broken or leaking exhaust pipe to avoid harmful emissions. A worn-out exhaust manifold gasket is also a common cause of exhaust leaks. Refer to this guide to fix exhaust manifold gasket leaks.

Cause: If you smell something sweet like a syrup, your car might be leaking coolant. Coolant or antifreeze contains ethylene glycol, which is a chemical compound with a sweet smell. When there is a leak in the cooling system, the coolant can drip, causing a sweet smell that is difficult to miss. This can happen due to loose or torn hoses and clamps, a leaking thermostat gasket, or a failing head gasket. Other possible locations for a leak can be the radiator cap or the radiator itself. However, you can smell a leaking radiator outside the car and not in the cabin. If the odor is very strong inside the passenger compartment, the heater core might have gone bad. The odor can also be accompanied by a temperature gauge light, a check engine light, or a coolant level warning light. 

What To Do: A leaking coolant can lead to engine overheating and cause extensive damage to the engine. If your car smells like sweet syrup, your cooling system is at fault and needs to be checked immediately. It's not advised to drive your car with a leaking coolant and a malfunctioning cooling system.

Cause: An acrid, smokey smell resembling burning oil can indicate an oil leak. The leak can be caused by various reasons, like a loose drain plug, an oil filter that wasn't fitted properly, worn-out engine seals, a leaking valve cover, etc. Worn-out and damaged seals allow the oil to drip over the hot exhaust manifold, causing it to burn and emit an acrid smell. An easy way to determine an oil leak is by checking under the vehicle and on the floor for oil stains. Sometimes, while driving, you may notice smoke coming from beneath the hood.

What To Do: Check the oil cap and filter for leaks and the engine oil dipstick as well. If you notice low engine oil levels, top them up. Repeated low oil levels can be a clear indication of leaking oil. Running your vehicle with leaking oil can deplete your oil levels, which can be detrimental to your vehicle's performance and can lead to engine breakdown and hefty repair bills.

Cause: The smell of a burning carpet indicates an overheating braking system. You can notice this smell when you drive aggressively, on curvy mountain roads, or while driving down a steep road. The burning smell can also be caused by dragging or sticking brake pads. While a burning smell is normal under intense braking conditions like racing or driving down a mountain pass, you shouldn't smell this under normal driving conditions. If you notice a burning smell while driving on a flat road, you may either have your handbrake engaged or the brake drum or brake calipers may be failing. Do not confuse this smell with that of burning paper. If your car smells like burning paper, it could be due to worn-out clutch plates.

What To Do: The best course of action is to pull over to the side of the road and let your brakes cool. It's not advised to drive on hot brake pads as it can lead to brake fade. Drive home carefully and change your old worn-out brake pads and rotors. Also, check for brake pad engagement and retraction. You can do this with the wheel jacked up. Spin the wheel and observe. If it stops immediately, then there may be a brake sticking issue. Repeat on each wheel and get the vehicle inspected by a professional.