Exhaust in cabin

I have been getting exhaust in my car cabin since last fall. It is worst when I first start up the engine. Once I get driving, it’s not so bad. Switching off the heat or recirculating the air does nothing to change things. I used a CO detector in the cabin and the alarm didn’t go off, but it still worries me that I might be breathing in carbon monoxide. And none of the shops have been able to diagnose it, let alone fix it. The first shop installed a new ‘flex pipe’. The dealer thinks it’s coming from a gasket near the flex pipe. The exhaust manifold is not cracked. A muffler shop said there was no leak. Is it possible that exhaust is somehow getting mixed into the air via a faulty valve or vent? Thanks!

Is it possible that exhaust is somehow getting mixed into the air via a faulty valve or vent? Thanks!

In order for that to happen…the exhaust MUST be leaking.

If you’re smelling exhaust in the car…then there’s either a leak…OR the exhaust is coming in through a rear window after it exists the tail pipe.

It’s possible that what you’re smelling is oil or power steering fluid on your exhaust headers. That will get picked up by the air intake as you drive. Another possibility is your trunk lid seal is bad and exhaust from the tail pipe is being drawn in. Your car is newer, not really likely that either of these is a possibility. But then, neither is a broken exhaust pipe. Was the car wrecked or damaged in some way? Any kind of visible leaks on the engine or near the headers? If the smell is bad when you first start the engine, is it only this bad when the engine is cold or when you are sitting at idle too, like waiting for a traffic light?

On a car this new I wouldn’t think fumes could get inside the car except by coming in the air vents somehow. All the seals should be in good shape.

Would the local fire department have something they could use to detect smaller amounts of CO2 than what home detectors can?

If the car is louder than what you are used to, you have a simple exhaust leak somewhere in the exhaust system. This begins with the exhaust manifold and ends at the tailpipe. Any exhaust leak along this system can cause exhaust gases to build up in the cabin. Even leaks from the muffler or tailpipe.
Your nose is a pretty good instrument. But it can’t smell carbon dioxide. In fact, you could very comfortably die breathing CO2, since even your blood would be fooled to believe that it is absorbing a nitrogen/ O2 mix (along with CO2) until you fell asleep and died.

You have an exhaust leak, and you are smelling exhaust. Fix that.

The killer in exhaust is carbon monoxide (CO), not carbon dioxide (CO2).

Correct. The only way CO2 can kill you is it becomes concentrated so you do not get enough oxygen. Good catch. Five stars for you.

So, though he needs to go through the troubleshooting ideas you guys have given him, I tend to think it will be something coming in the air vents.

In 1998, we moved to McAllen from the Midwest. We rented a big yellow truck, loaded it up, and put our big Bonneville wagon on a trailer behind. When we stopped at night, I heard a noise, and when I investigated, I found our CO alarm in the back of the car, and enough CO had gone into the car, on a trailer behind the truck, that it fired off the alarm. So, I tend to think the fact the CO alarm did not ring is because it isn’t CO, but fumes as someone has suggested.

But, better safe than sorry. Give yourself plenty of air in that car until you find the problem.