Need help with Exhaust fumes in the car with windows down

Terrapin88

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Hi all.

I've had my 98 Conti a little more than a week. While driving with the windows down I can smell exhaust fumes and I am trying to track down the cause of it. With windows up, all I can smell is the leather and my air freshener. With windows down at all, all I can smell is exhaust fumes. We all know the dangers of breathing in exhaust fumes, so getting this dealt with is priority one for me.

I took the car to a trustworthy muffler shop and they found a leak from the flex pipe and one on top of the cat that's just in front of the flex pipe. They replaced the flex pipe and welded a patch on the rot hole on the cat. They said the rest of my exhaust is solid and they could find no other leaks. I left the shop and got a mile or so away and I could smell the fumes again. I won't have time to bring it back to the shop till monday, but If they didn't find another leak the first time I don't have a lot of confidence they will find it a second. Not saying they are incompetent, just saying that they are human so it's possible they may have missed another leak. They did spend a good amount of time looking though.

This is what I know so far:

1. I have replaced the PCV and VC breather hoses. I also replaced the main large emission hose that goes from the throttle body to the firewall.

2. According to the shop, my exhaust from manifold to mufflers is "solid" and now leak free.

3. It doesn't smell like unburned gas or burning oil (like if I had an oil or tranny leak dripping on the hot exhaust)

4. I ONLY smell the fumes when I am moving and I open the windows, be it a crack or all the way down.

5. With the windows up I smell no fumes at all regardless of whether I have the heat/AC blowing or not, moving or stopped.

6. My quarter panels are rusted out on the bottom under the car in front of both rear wheels. ( I missed that when buying the car because the body looked so clean. I should have stuck my head under the quarters and looked anyway. Duh) Anyway, making some kind of repair to cover those holes is on my to do list.

My thoughts on what's possibly going on:

When I open the windows while driving a vacuum is created in the cabin because...

1. Exhaust is being sucked in from the tailpipes through the holes in the quarter panels.

2. I have a worn out trunk seal which is letting fumes in.

3. A hole somewhere under the trunk.

4. A hole in the firewall (thought if I have no more leaks I'm not sure how the fumes could makes it from the tailpipes to the firewall)

5. My tail pipes are too far under the rear bumper. I would think they should be at least flush with the outside of the bumper, but they are not.

Any ideas guys?
 
I go with #1. Think of the rear window on an SUV like a 4Runner or an old 70s station wagon -- roll it down while driving and the fumes will run you out of the car.

If there is nothing stopping fumes from entering the cabin from the rear wheel wells then that's what is happening.
 
That is what I am thinking too. I didn't have the time today, but I am going to use some foil tape tomorrow to try and seal those holes. If I do not smell exhaust after doing that I'll know that's where the problem lies and make a more permanent repair. Youtube is teaching me how to do body work. Oh joy.
 
Figured it out. Exhaust is being sucked in from the tailpipes through the holes in the bottom of the quarter panels. I did a foil tape job on the holes and I no longer smell the exhaust. No I need to fill and seal the holes. I may use spray foam to fill the cavity in the panel and a fiberglass sheet with bondo to seal over holes.
 
i noticed a smell as well and i dont have the same circumstances though. first off i have no known exhaust leaks the shop said it was all good . i have a 2000 lincoln conti. and the only time it happens is (with the windows up) a/c off or on , that doesnt seam to make a difference , when i go to get on the interstate (i75) if i "put my foot in it" i get a very strong almost acrid odor in the cabin and it is not a raw gas smell ..... i dont normally do that :eek: , i just wanted to get an idea of what the car would do, so i need to open the windows to get rid of it it only happens when i push it to a high speed and i have not opened it up all the way yet . i was thinking that maybe the trunk lid gasket ???????? but it looks good . there is no rust anywhere on the car door gaskets and windows all look good. any ideas?? thanks guys
 

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