Exhaust fumes smell when heater is on

Hi all,

I need some input. My car has a slight exhaust fumes smell coming through the vents when I turn the heat on.

This just started yesterday after I switched the temperature control from cold to hot. The smell only appears to happen when burning heat.

What could this be? Would the EGR valve or housing cause this issue? I backed into a curb last month and since my car has been louder upon acceleration.

If this is the first time you turned the heat on for several months it may be dust baking off the heater core, if should clear up soon. Same thing happens at home when your furnace comes on the first time. If this continues get your car to a mechanic ASAP to check for an exhaust leak which can be dangerous.


You broke your exhaust and the fumes are getting into the car. This needs to be repaired immediately because these fumes can sicken or kill you. Drive with the windows open on your way to a repair shop.


Also,check around the valve cover gasket in case some oil is leaking and dripping down on the exhaust manifold.I always get a burning oil smell through the vents when this happens.What is the make,model,year of your vehicule,milage?.


Thanks for the quick reply. I edited my original post to include more info. I drove the car maybe 30 minutes total before I started to smell the slight scent of exhaust fumes. This has never happened before when switching from cold to hot. I don’t switch the vent dial to heat, I leave it on max and just switch the temperature dial from cold to hot.

I’m not sure if this is related, but about 3 days ago I had a friend help me clean the area behind the EGR valve a bit (I think it could use a more thorough cleaning) in an effort to remove some of the build-up.

Cleaning it did appear to help with the acceleration issue that I was having, although it did not eliminate it completely. The check engine light went out immediately after cleaning and I had better acceleration, but eventually the light came back on.

I started having the issue with acceleration after replacing the EGR valve. For example, if I was trying to do a hard acceleration onto the interstate while merging the engine seemed to stutter out and I would have to lift my foot off the accelerator and press it down again and do that process repeatedly until it got up to about 35 miles per hour and then it would accelerate normally. If I keep accelerating, the check engine light starts blinking. I’ve been driving like this for the past five months since replacing the EGR valve. I’ve been doing more driving lately, so I decided to have the EGR valve area cleaned.

There was no issue with acceleration until I had the new EGR valve put on about 5 months ago. The only reason I had the EGR valve replaced was because that was supposedly the reason why my check engine light was coming on according to AutoZone when they did the check engine light testing.

I saw a video on YouTube that said one reason the EGR code was coming up could be because the housing behind needed to be cleaned versus the EGR being bad.

I backed into a curb about a month ago and then my car was immediately louder afterwards upon acceleration. I thought maybe it put a hole in the muffler? Could these issues be related to the reason why I am smelling exhaust fumes only when the heat is on?

Its a 1997 Buick Century. I’ve had the heat on for short periods a few times since backing into the curb. Yesterday was the first time I ran the heat longer.

I figured I need something fixed but yesterday was the first time smelling the fumes although I have ran both heat and air since first backing into the curb.

Any idea on what they will possibly need to fix when I take it into the muffler shop? I just like to have an idea of what might be going on so that I don’t get charged for things that I don’t need.

Mileage is over 200,000 miles

Not without seeing the vehicle in person can anyone say what needs fixed or replaced . The muffler shop will tell you and then you either agree to the repairs or get a second opinion.

Thanks to you all for the input. I went to a muffler shop. They showed me where the muffler was bent up. They also said I needed some sort of plate that’s a part of the exhaust system but up near the front of the car.

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