Why Is There An Exhaust Smell in Your Car?

You may smell exhaust in your car if you have a damaged catalytic converter, a bad heater core, or a leaky exhaust system.
Written by Abbey Orzech
Edited by Pat Roache
An exhaust smell in your car can come from several sources: an exhaust leak, a faulty catalytic converter, or a bad heater core.
  • Take your car to a mechanic
    right away if you notice the smell of car exhaust or other odd odors in your vehicle to avoid further damage.
  • The smell of exhaust can be caused by damage to your catalytic converter, heater core, or any part of your car’s exhaust system—including the exhaust pipe.
  • Smelling exhaust in your vehicle while driving or idling is not normal, and it could expose you to carbon monoxide poisoning.

Understand the type of exhaust smell

You’ll want to address any out-of-place car smells as soon as possible to avoid lasting consequences. Any repair will be easier to deal with if you can first identify what the smell is:
  • Regular exhaust smell: Regular exhaust smell has a musty, smoky scent to it. If you catch a burning smell not paired with any other particular scent, it’s likely you’re smelling regular exhaust from a damaged exhaust system.
  • Gasoline smell: The pungent, sharp scent of gasoline can infiltrate your car’s cabin from something as simple as a cracked fuel cap or worn-out gasket—or something more involved, like a fuel leak, imbalanced rich air/fuel ratio, or faulty fuel injectors. Black smoke from your muffler may also accompany the gasoline smell.
  • Rotten egg smell: A failing
    catalytic converter
    won’t be as effective in removing hydrogen sulfide from your car’s exhaust gasses. This can produce a noxious smell of rotten eggs that may permeate your car cabin.
  • Sweet exhaust smell:
    has a distinctive sweet smell. If the exhaust smell you're dealing with has a hint or more of sweetness to it, you could have a damaged cooling system. 

Why is there an exhaust smell in your car?

Let’s go over some of the most common reasons for an exhaust smell in a car:
  • Faulty catalytic converter: Catalytic converters change toxins and pollutants found in exhaust gases into less harmful compounds before exiting the tailpipe. They can become clogged, contaminated, overheated, or worn down over time and may require a
    repair or replacement
  • Bad heater core: The heater core is a part of your vehicle’s coolant system and can leak exhaust into the car’s cabin if damaged. If you notice antifreeze puddles under your parked car, you’re likely dealing with a
    faulty seal in the heater core
    that needs to be replaced.
  • Exhaust leak: If you notice a loud noise from your engine when you start it or accelerate, it could be an exhaust leak. Have this checked out by a professional—the complexity of the exhaust system can make this problem hard to diagnose. 
Breaking it down: A properly functioning vehicle exhaust system should divert harmful gasses coming from your engine. You could have a problem with any one of the components of your exhaust system if you notice an exhaust smell inside the cabin of your car, and should hire a mechanic right away.

What to do if you smell exhaust fumes in your car

Here’s what to do if you smell exhaust fumes in your car:
  • Identify the smell: Is it eggy or sweet? Musty and hot or sharp and pungent? Take detailed notes of the offending smell to make the repair process simpler.
  • Determine the source of the problem: After you’ve identified what the exhaust smells like, call a mechanic or do some Googling to try to figure out where it’s coming from. Also, double-check to ensure the smell isn’t coming from another vehicle around you.
  • Check window and door seals: The seals around windows and doors break down over time. If you notice an exhaust smell while all the windows and doors are shut, check the seals to make sure they aren’t allowing harmful emissions into your cabin.
  • Take your car to a mechanic: The best way to know for sure what you should do about the exhaust smell permeating your car’s interior is to bring your car to a certified mechanic as soon as you start smelling it. With up-to-date diagnostic technology and invaluable work experience, a professional mechanic should be able to pinpoint the problem and offer solutions to remedy it.
Stay safe: If the exhaust smell is really bad, you may wish to
have your car towed
. Inhaling toxic fumes for too long can cause a loss of consciousness—an obvious hindrance to safe driving.
MORE: How to decide if you should take your car to a repair shop or a mobile mechanic
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