What Does the Smell of Your Exhaust Mean?

April 2, 2020

Exhaust is something that people don't often think about, but when it starts to smell different--or when you smell it somewhere you shouldn't--it's cause for concern. While decoding what an exhaust smell might mean can be helpful, there's one constant: if your vehicle's exhaust starts to smell different, you should schedule a service appointment right away. Below, we'll take you through four common smells and what they might mean.

4. Regular Exhaust Smell

Normally, exhaust has a sort of smoky, musty smell. It's hard to describe, but relatively easy to identify by smell. If your exhaust smells like exhaust normally does, you may not have anything to worry about . . . depending on where you can smell it. If you can smell exhaust inside your vehicle's cabin, you may have an exhaust leak. Since exhaust carries carbon monoxide, this is a serious issue that should be addressed immediately. Pull over and turn off the engine as soon as you can, and then call for a tow truck.

3. A Gasoline Smell in the Exhaust

If the exhaust coming from your vehicle smells like gasoline, it's often due to an overly rich air/fuel ratio. This means that either too much fuel or too little air is getting into your vehicle's combustion chambers. This can be caused by problems like damaged and leaking fuel injectors, a clogged air filter, a bad mass airflow sensor, or a number of other problems. In addition to a gasoline smell, you might also notice black smoke coming from the tailpipe.

2. Sulfur/Rotten Egg Smell in Exhaust

There's a reason brimstone has been associated with wrath: it's a foul smell that often means trouble. This is true in cars, as well! If your exhaust has the distinct noxious smell of rotten eggs, sulfur, or sewer gas, it's likely due to a damaged catalytic converter. When combustion happens in your engine, harmful gases like hydrogen sulfide (which contains sulfur) are created. The catalytic converter takes these gases and converts them into less harmful forms. If the catalytic converter isn't working, this conversion may not happen--hence the sulfur smell. Not only will a damaged catalytic converter cause your car to smell, but it can also reduce performance, increase pollution, and cause your vehicle to fail emissions tests.

1. Sweet-Smelling Exhaust

A sweet smell may be more pleasant to your nose than the smell of gasoline or sulfur, but it can still mean trouble. Exhaust that smells sweet could mean that your vehicle has a leaky or damaged head gasket. This could cause coolant to be burned up inside your vehicle's combustion chamber, releasing the sweet smell of antifreeze with your exhaust. In addition to the smell, a leaking or blown head gasket will often release billowing clouds of white smoke from the tailpipe.