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Exhaust fumes in cabin solved!!!


Derek

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For me that is.

I've been battling with this problem for years. In Florida I mainly run with the windows up and the air on so it hasn't been too much of a problem. But with the windows down and during down shifts it was getting pretty bad. I had made all the usual repairs. New weatherstripping, sealed the tail ights, checked for holes with a flashlight, etcetera etcetera. All to no avail. I then came across this post by

Zs-ondabrain http://www.classiczcars.com/forums/showthread.php?t=29708&highlight=exhaust+fumes

“Here is one thing you can do. Get a smoke machine, a shop vacuum and some cardboard.

Cut the card board to fit in the window opening with the window 1/4 of the way down. Cut a hole the size of the vacuum hose into the card board and slide the card board into the felt groove in the upper part of the window frame. Then tape the lower part of the cardboard to the upper part of the open window.

Turn on the vacuum. Start the smoke machine and blow the smoke to the suspected areas and there ya go. Or have someone on the inside watching for the exact spot that the smoke comes in, while you're out side with the machine.”

The only thing I changed was I was on the inside of the car and my buddy was on the outside working the smoke machine.

As I laid in the back of of the car my thoughts quickly switched from wondering if I wasted $45.00 on the smoke machine to “ I hope I can get out of here alive” as I was immediately engulfed by smoke. Okay I know the smokes non toxic but it was a bit freaky! We aired out the car and decided to go for a more measured approach. This time I was able to spot the areas where the smoke was coming in. In my case it was the body seams between the rear body panel and the inner floor that were leaking.

I had put a new rear body panel on the car years ago and didn't do a good enough job of sealing the seams. The biggest culprit was the very bottom seam. This is the one you see if you look under the car and follow the inside of the panel upward. This is also where the bumper brackets mount. Although this channel doesn't directly lead into the cabin, the ends are open and spill into the ¼ panels under the tail lights.

It then became a game of sealing leaks and the re smoking the car. All told I found 3 minor and 1 major leaks that I probably never would have located without the smoke machine. Now's the time to buy one because of Halloween. The party stores all stock these things.

This really works!

Derek

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Derek, What were you smokin? I had the same problem with the windows up but when I replaced my tailghts with new ones and gaskets and sealed up the back panel most of it went away. I still get some smell with the windows down when I'm decelerating I guess it's areo effect. If you still got the stuff maybe I can come down and we can smoke my car.

How's your car coming along and that manifold. Take care Bill

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Derek, What were you smokin? I had the same problem with the windows up but when I replaced my tailghts with new ones and gaskets and sealed up the back panel most of it went away. I still get some smell with the windows down when I'm decelerating I guess it's areo effect. If you still got the stuff maybe I can come down and we can smoke my car.

How's your car coming along and that manifold. Take care Bill

Man my car hasn't been that smokey inside for a lot of years! But that's another story.

I bought one of the smoke machines and plan on keeping it. Your welcome to bring your Z over and we'll have a smoke out.

The wife and I took the car out to dinner last night and drove home with the windows down. Not the slightest bit of exhaust fumes were in the car. She's more sensitive to the smell than I am and she didn't smell a thing.

When I get a little more time I'm going to smoke the rest of the car and get the rest of it sealed up.

The manifold is on hold right now as I'm really busy with paying pattern work. Although I'm carving an intake pattern right now for a Desoto Hemi. So I am working on an intake just not mine!

Shoot me an email and let me know when you want to come over.

Derek

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Hi Derek:

Thanks for posting the info. It's interesting to know that the seams were actually leaking.

FWIW,

Carl B.

Hi Carl

Yea it was really freaky. Ultimately it was my poor job of sealing when I put the rear body panel on but three of the seams were really tight but smoke still came pouring through. It's probably debatable whether these were leaking exhaust or not. The large seam along the bottom was probably the main culprit but as the many posts can attest no two cars are the same when it comes to exhaust leaks. I really went over the inside of the car with a fine toothed comb and never spotted these problems.

You have to wonder about the condition of some of the seam sealer on these older cars though. I'm convinced that this is probably the only way you can truly solve the leak problem in a methodical way.

One thing is that the lower seam is part of the rear bumper mounts so if there's been any kind of damage to this area there is the potential for exhaust leakage. I didn't bother trying to seal the seam. I shot some spray foam into the ends of the tubes and this sealed it right off. I removed the rear marker lights and this gave me a pretty straight shot into the tube.

Things like spoilers and long tail pipes are just band aids that mask the problem.

I've had this car since 1980 and I can't remember the last time I could drive it with the windows down and not get some sort of exhaust smell.

I'm really psyched!!

Derek

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  • 4 months later...

I never thought of using a Halloween smoke machine.

I tried something very similar to this last summer, but I removed the C pillar air extractor emblems and taped the shop vac hose to one side of the car and taped off the other side. Unfortunately, I didn't have a helper, so I tried to do it simply by looking through the hatch glass with a flashlight for a smoke trail with no luck. I didn't feel comfortable getting inside the car during the test since I was using a chemical reaction HVAC smoke bomb rather than a Halloween smoke machine. I think I will try again this spring while inside the car.

I did extend the tailpipe which greatly reduced the fumes in my car, but I'd like to completely eliminate the problem like Derek did.

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I"ve been fighting the fumes in the car issue too since I got my car. I extended the tip and replaced the door and trunk seals and I no longer smell it with the windows up, but as soon as the windows come down, its smoke-out season. Once the weather gets better, I plan to try the smoke machine approach and see if I can fix it.

Greg

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Derek, like many of us, I have been fighting this same thing for a long time . I shot POR in the same channel on my Z through the marker light holes in the fender. However I still get a little fumes . I am going to try the foam in the ends of the square channel and see if this takes care of it. Thanks for the heads up.

Gary

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  • 1 year later...

I put masking tape over the tail light area (inside of the Z) and covered the hatch vents too (I have a '70 with hatch vents, not the 71 with vents on the pillar) and the car went from undriveable (due to fumes) to now, very little fumes and none with the windows open.

So now I will replace the tail light gaskets. I went to try to rempve the assembly and found that the bolts rotate freely but do not come out. What gives? Any advice?

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Sounds like the plastic housing has been broken where the nuts are fitted. If you haven't removed your tail light cover/valance/surround, you'll need to do that (it's the 3 black or gray pieces that surround your taillights and license plate on the outside).

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