Exhaust getting into interior

[Jack Ryan]

I need help. 1965 300 4dr HT exhaust getting into the interior. The only thing that seems to help is running fan with windows shut and floor vents shut. Any other combination and after a short drive my clothes smell like exhaust. Thought it might be blowby escaping from valve cover breather, rerouted that into air cleaner intake but to no avail. No audible exhaust leaks before the muffler. It's possible that there are some in the muffler and tailpipe that I have not discovered. Car was quite rusty, is it possible that it is coming from the end of the tailpipe back into the trunk? Don't want to spring for a new exhaust if it is not going to fix the problem. Thanks.

 

[cbarge]

If you have holes in the trunk,or the trunk weatherstrip is petrified or missing you will get fumes in the cabin with windows down...Kinda creates a vacuum.
Holes in the floor will do the same thing especially if the top of the mufflers have holes that you cannot see.
I always run the end of the tailpipes 2-4 inches past the bottom of the rear bumper too.

hope this helps

 

[4spd300J]

As in the above post, any gap in the trunk seal will draw enough fumes in the cabin to make it seem like the exhaust comes out of the dash. That's why wagons ran the exhaust out the sides instead of straight out under the bumpers.

 

[The Goose]

Forget stinky clothes - this can kill you. You can smoke bomb the exhaust and check for leaks. We do that to check for leaks in cabs on heavy equipment. It’s not as big a deal today as back in the good ol days. Back then Rusty pipes cost thousands of lives. Be careful bud...

 

[1970FuryConv]

If you suspect a plugged muffler, put a vacuum gauge on the intake and slowly increase engine speed. Vacuum will drop toward zero from an idle vacuum of around 17hg. Old mufflers can look OK from the outside but have a lot of rust from condensation on the inside.

 

[cbarge]

Old mufflers can look OK from the outside but have a lot of rust from condensation on the inside.

...Or plugged by mice nests..

 

[Jack Ryan]

Hey thanks all, gives me someplace to start, actually lots of places to start. Has not killed me yet, only a little dizzy.....kidding.

 

[cbarge]

 

[fury fan]

Old thread, but wanted to respond for future folks that might have this problem...

Any water leaks on the front floorboard area?
A rusty cowl is another way engine compartment smells can intrude, and this can include smells from oil drips and weepy gaskets.
Look under teh dash with a pencil flashlight and look for holes up high - but be aware, there are lots of things under there that can block your view and hide a hole. Runnign a garden hose down the grille-vents at the windshield base provides a good clue. But be aware that if the bottom of the cowl (bottom of fender area) is plugged with leaves and silt, water can come in from the floor vents - which is a different problem. What you are looking for is garden-hose water trickling down the carpet into the feet area.

And IMO a rich-running engine makes this all the worse.
Does your exhaust water your eyes when standing behind the car? If so - too rich and/or not a complete burn of fuel.

 

[1970FuryConv]

Old thread, but wanted to respond for future folks that might have this problem...

Any water leaks on the front floorboard area?
A rusty cowl is another way engine compartment smells can intrude, and this can include smells from oil drips and weepy gaskets.
Look under teh dash with a pencil flashlight and look for holes up high - but be aware, there are lots of things under there that can block your view and hide a hole. Runnign a garden hose down the grille-vents at the windshield base provides a good clue. But be aware that if the bottom of the cowl (bottom of fender area) is plugged with leaves and silt, water can come in from the floor vents - which is a different problem. What you are looking for is garden-hose water trickling down the carpet into the feet area.

And IMO a rich-running engine makes this all the worse.
Does your exhaust water your eyes when standing behind the car? If so - too rich and/or not a complete burn of fuel.

Weird story: I had a car recently, where someone had used too much starter fluid or had a really bad tuning job. But the muffler outer housing was blown open, like an open clam shell facing the outside of the car. The car was missing and running terribly and had starting problems. Replaced cap, rotor, spark plugs and coil. Adjusted carb idle, which was too lean. Turned out a stripped positive primary coil stud and bad connection was causing start up problem, but when driving the car, it still missed. Finally, I looked inside the clam shell and decided that the innards of the muffler were partially blocking the midpipe. I used a narrow blade shovel (I'm sure every pro mechanic has one in their tool box) to pry the innards of the muffler out of the clam shell. I started the car and smoke billowed up from the the engine compartment and around the sides of the car. I had to open the driver's door, because it was getting into the passenger compartment. Finally, the engine burnt up all the bad stuff collected in the y-pipe and mid-pipe. After that the car cruised just fine. Loud but fine.

 

[Jack Ryan]

Any leads on trunk seal material? Thanks.