Car Exhaust Smell: Understanding Where the Problem Lies

June 17, 2020

A car exhaust smell can be due to many different things. The car exhaust port is important as it neutralizes many of the harmful fumes that come out of the engine. If you notice a nasty smell from the exhaust, such as a rotten egg smell, then there is a problem. Besides rotten eggs, a sweet smell or a smell of gas from the exhaust are also typical signs that something is wrong. It is important that you have the car fixed immediately when you start to notice an odd car exhaust smell as they can be linked to some major problems in the exhaust or engine.

Rotten Eggs

The smell of rotten eggs is due to a compound called hydrogen sulfide. This comes from the small amount of sulfur that is present in the fuel. Normally the sulfur is converted to sulfur dioxide, which has no odor. When the converter breaks or the filtering layers have worn down inside the converter, the sulfur is not transformed into the odorless form. Therefore a strong rotten egg smell is produced. Another possible cause for this smell may be that the converter is plugged. Unfortunately you cannot repair a converter but need to have it completely replaced. Two other causes of rotten eggs besides a broken catalytic converter include an engine that is running too hot or a broken fuel pressure regulator. You can easily deal with the fuel pressure regulator by replacing the fuel filter.

You Have a Leak

If you notice a very strong exhaust smell in the car then you probably have a leak in the exhaust system. There may be a hole in the exhaust pipe, tailpipe, or muffler. You also may have worn down a part of the car interior which is letting the exhaust in. Check the door seals and the rear doors. If carbon monoxide is leaking into your car this is serious as this chemical is highly toxic to humans.

Funky Car Smell? Tips for Finding the Source

Problems with the Heater Core

There are several issues that may cause car smells from the heater core. If you notice your heater is producing an antifreeze burning smell then there is a good chance that antifreeze is leaking into the heating system. A leak can occur from a hose to the heater core or the heater can be cracked. You will normally be able to see antifreeze dripping onto the ground or running down the side of the heater core. Your heater core could also have broken seals. Most of the time a sweet smell, such as cinnamon, maple syrup or butterscotch is an indication that there is a leak in the heater core.

Gas Smell from Exhaust

Sometimes you may find that the exhaust smells like gas. This is normally a problem with the air and fuel mixture as your fuel injector may be sending too much gas through the engine and not all is burning. This can easily be fixed by having your engine properly tuned. You also may not be using the correct brand of gasoline. Therefore the engine and exhaust are not working properly which results in gas like odors emerging. You may also find that the fuel injector is clogged and needs cleaning. Another cause of this gas smell is a stuck choke if you have a carburetor.

Related Questions and Answers

What Does Car Air Conditioner Gas Smell Like?

Car air conditioner gas smells a bit like ether. The gas used in modern day cars is R-134A. This replaced the odorless freon back in the 1990s. If there is a smell in your vehicle that is a bit medical in nature, it could be that the air conditioner is leaking. If the smell is more of a moldy smell, it's possible there is a bacteria issue in the system. Bacteria can be dangerous so it is best to have the system checked out by a professional. While more environmentally friendly than freon, R-134A still contributes greenhouse gases to the atmosphere.

What is Happening When There's a Burning Rubber Smell from a Car?

A burning rubber smell from a car can be caused by any number of things. A burning clutch often smells like burning rubber. It is also possible that oil is leaking onto the engine and burning off. Many times burning oil will give off a burning rubber smell. Finally, the most common cause of this problem is an engine belt. Various belts in the engine, when failing, heat up and give off a smell of burning rubber. Any of these problems can result in further damage to the engine if they are not fixed in a timely manner. If your car is giving off a burning rubber smell for more than a day or two, you should take it to a mechanic to have it checked out.

Is a Fuel Smell In a Car a Serious Problem?

A fuel smell in a car can be an indicator of a more serious problem. It is also possible that you somehow tracked gasoline into the car when filling it up. If the smell persists for more than a day or two it is a good idea to have a professional check the vehicle out. A couple of things that might cause a gas smell would be a leaking gas line, or leaking fuel injectors. If this is the case, it is important that the car be serviced by a professional. In some cars the fuel injectors may have over-injected the engine and the extra gas has leaked out. The smell should go away after the gas burns off.

Is it Bad if There is a Gas Smell in My Engine Oil?

Yes, if there is a gas smell in the oil of your car there could be a serious problem. If the fuel line is leaking or the injectors are leaking gas, it can get into the crankcase. If this happens your oil will smell like gas. Pulling out the dipstick and giving it a sniff should confirm gasoline in your oil. If this is the case, you should get the vehicle to a mechanic as soon as possible. They will need to drain and change the oil. In addition, they will need to find and fix the fuel leak. Gasoline in your oil can result in scored cylinder walls.

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