Why Do Some Cars Have Really Smelly Exhaust Fumes?

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Most cars have minimal odor to their exhaust. It smells like, well, exhaust, but it’s not terribly strong. This is thanks in large part to the catalytic converter. However, some cars seem to have really smelly exhaust fumes due to a number of different reasons (depending on the smell in question).

Burning oil

If an engine is burning oil (due to leaking seals), then you’ll definitely notice the car has really smelly exhaust fumes. You may also notice that it creates smoke from the tailpipe (bluish in color).

Failing catalytic converter

Ever been riding along and suddenly smell rotten eggs? If so, you’re behind (or beside) a car with a failing or failed catalytic converter. Sulfur is found in gasoline, and is turned into hydrogen sulfide in the combustion process. However, the catalytic converter changes it into sulfur dioxide. This has no odor at all. As the cat fails, it stops changing hydrogen sulfide into its odorless counterpart and the result is a strong smell of rotten eggs from the exhaust.

Burnt antifreeze (hot and sweet)

If what you’re smelling is sort of “hot and sweet,” it’s probably engine coolant. There are many ways this can happen. A pinhole leak in a coolant hose can spray antifreeze onto a hot engine component, which boils the coolant away and creates that smell. It can also contaminate oil and be burned in the engine that way.

It’s a diesel

Diesel exhaust smells much stronger than the exhaust from a gasoline engine. You’ll also notice that the exhaust is darker, particularly on large trucks with powerful diesel engines.

Gasoline

If the exhaust smells like gasoline, it’s a sign that the air/fuel mixture is off in the engine and too much fuel is being added to too little oxygen.

If you notice any of these smells coming from your exhaust, you should have the problem diagnosed as soon as possible. If you notice there’s a strong smell of exhaust in the cabin, you should also have this diagnosed and repaired quickly. It’s a sign that your exhaust system is damaged. Keep the windows down to prevent carbon monoxide from building up in the cabin.


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Sean

16 years of experience
89 reviews
Sean
16 years of experience
Chevrolet Equinox - Exhaust fume odor in car - Arlington, Virginia
Sean was very kind and honest. For a first time customer of Your Mechanic, working with Sean was a very pleasant experience.
Honda Civic - Exhaust fume odor in car - Annandale, Virginia
Great guy very informative and knowledgeable

Rigoberto

10 years of experience
739 reviews
Rigoberto
10 years of experience
Hyundai Santa Fe - Exhaust fume odor in car - Glenview, Illinois
Rigoberto was communicative, punctual, and considerate of my time. He quickly and thoroughly assessed the problem and explained it well to me.
Chevrolet Traverse - Exhaust fume odor in car - Lombard, Illinois
knew what he was talking about

Mazyar

7 years of experience
213 reviews
Mazyar
7 years of experience
Ford Escape - Exhaust fume odor in car - Stone Mountain, Georgia
Did a great job....and great demeanor too. Thanks....I did feel a little sheepish not finding that oil cap!

Josh

15 years of experience
29 reviews
Josh
15 years of experience
Saturn L300 - Exhaust fume odor in car Inspection - Naples, Florida
Josh told me exactly what was wrong with my car and the repair was done quickly and even got something better to fix my problem. I am satisfied with his work.

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