1969 mach

[rchevy61 10]

Hi all, I just got done restoring a 1969 mach 1. I have been fighting a very frustrating problem for over a year now. When i drive it, and open the windows, i get a bad exhaust smell.??? I have gone over and over all the simple stuff,, no leaks I took the wing off the deck lid, that made a big difference, but its still there. I have been working on cars for over 35 years, and have never been so frustrated with something. This car does have a aftermarket AC Unit ? There is no smell at all with the windows closed, and the heat or AC on. (Cabin Pressure)

 

HELP!!!!!!!!!!!

[etel64 10]

Sounds to me you have gone to extreme measures to figure this out. SO, Im stabbing in the dark but are there any open spots in the trunk area? the way the rear valance is mounted it would seem to me this is a perfect scoop for any air.

 

Pesky problems like this, are they supposed to be part of the enjoyment factor?:001_rolleyes: I doubt it. You will figure it and am sure you will share your results with us.

[rchevy61 10]

Nope, i have gone over and over it

[LindenBruce 27]

Okay, where do your tail pipes terminate? Any pics? Bruce

[danno 128]

Maybe temporarily wire on some exhaust tail pipe extensions. The ends of the exhaust might not be in the airflow out the back they could be in teh airflow that gets sucked back forward. It does happen. Take an old tin can and use one of those hose clamps like on radiator hoses to extend the pipe another 6 inches. A simple test worth a try...

[Mike65 476]

I remember on my 68 GT Coupe I used to have when I ended the exhaust at the rear axle I would get exhaust smell in the car with the windows open but once I ran tail pipes out past the rear valance it went away.

[rchevy61 10]

Tail pipes go past rear valance, are even with rear bumper

[Pakrat 1,043]

So assuming that your test for leaks included plugging the rear and listening thru every section of the exhaust and that you were actually able to lesson the issue by removing the rear wing I still suspect the trunklid. If your seal isn't making contact all the way around then once you open the window and create a vacumm it would suck the fumes right in. Thinly coat your seal with something like say vaseline or even chalk, gently close the lid to the locked position, open it up and look along the base of the car for an area where the seal does not appear to be making contact, that would be your culprit. If you can't see an area like that then add something temporarily extra to the whole area like some cheap household foam window and door insualtion and go for a test drive windows down to see if it still there.

[PaleRider 12]

Assuming you checked exhaust manifold gaskets. Similiar issue on mine.

[50dan 25]

I'd say exhaust manifold leak.

[Powershift 19]

I agree with Pakrat. If removing your rear wing made a difference, and all the wing does is affect airflow at the rear of the vehicle, it would seem to indicate the fumes are getting in from the rear. The trunk seal would be the first suspect.

 

I know you can buy trunk barriers, which shield fumes from entering the passenger cabin, for some cars. If they are available for your car it may not be a bad option to try.