exaust in cab
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Joined: Dec 2007
Posts: 7,987
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From: Boise, Idaho
When you put on a new tailpipe, did it exit to the side, or straight out the back?
If it goes straight out the back, I'd recommend cutting it off and redoing the tailpipe. The aerodynamics of the Bronco cause exhaust straight out the back to get pulled back inside the vehicle, which can be very dangerous, if not deadly.
If it's exiting to the side as it should, it could be a leaking exhaust manifold gasket or emissions component in the engine bay that's gone bad.
If it goes straight out the back, I'd recommend cutting it off and redoing the tailpipe. The aerodynamics of the Bronco cause exhaust straight out the back to get pulled back inside the vehicle, which can be very dangerous, if not deadly.
If it's exiting to the side as it should, it could be a leaking exhaust manifold gasket or emissions component in the engine bay that's gone bad.
Senior User
Joined: Jan 2010
Posts: 259
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From: Great Falls Mt
Yes yes...exhaust must exit the side on a bronco. Also check rear window seals and inspect tailgate to make sure the bottom isnt so rusted out its sucking fumes in from there if your pipes go all the way to the rear...but check emissions and leaking exhaust components first.
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Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
What year and type of engine do you have?
Check the one way valves that come out of the exhaust and go into the smog pump. Look like this:
The valves inside can rust out, letting exhaust enter the engine bay.
If they go completely out, like mine did, they'll let exhaust out full force, which'll melt a bunch of other emissions components and you'll have burned and melted plastic on your hands, and lots of components to replace. Not fun.
Check the one way valves that come out of the exhaust and go into the smog pump. Look like this:
The valves inside can rust out, letting exhaust enter the engine bay.
If they go completely out, like mine did, they'll let exhaust out full force, which'll melt a bunch of other emissions components and you'll have burned and melted plastic on your hands, and lots of components to replace. Not fun.
Freshman User
Joined: Jul 2010
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i found a proble just like yours one day while ride the sun shined in and i could c ext comeing in the cab through the air vent i re sealed the air box on the passenger side of the fire wall with some heave seal that fix my problem new i belive they were wraped in insulation
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Posting Guru
Joined: Jul 2006
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From: Westminster,Md
There is also a tube between the back of the engine and the firewall, that connects the two heads and the above valve mounts to..rusts thru and leaks..can sometimes do bad stuff to wiring harnesses, give it a good lookover.
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Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
i found a proble just like yours one day while ride the sun shined in and i could c ext comeing in the cab through the air vent i re sealed the air box on the passenger side of the fire wall with some heave seal that fix my problem new i belive they were wraped in insulation
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
If the Thermactor check valve... (photo that Abandoned Bronco posted) in the crossover tube between the two cylinder heads just in front of the cowl/firewall fails it will allow exhaust back up through the Thermactor plumbing which will eventually do two things. 1) destroy the formed rubber hose that runs to the check valve and 2) melt the main engine bay wiring harness which runs across the cowl just above the valve. Might want to check that this is definitely NOT the case before too long because the electrical damage can be extensive and expensive. (This failure will also allow exhaust to be drawn through the cabin not only through any small holes but also directly into the ventilation system for the cabin because the intake for that system is the slots in the cowl between the hood and the windshield).
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
That's what happened on my '81. The 300 is pretty spacious and things are open and far away from each other, and this valve going out and melting things cost me quite a bit of money, probably in the $200 range for emissions equipment and such. I can't imagine what it'd cost on a newer engine with more components, or a V8 where things are closer together.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
In the 302 and 351 EFI trucks, the main engine wiring harness runs right over the top of the check valve in the crossover tube... You have about a day worth of driving with the check valve broken off or the hose removed before you melt down critical portions of the main engine wiring... maybe a little longer if its really cold out.
Senior User
Joined: Mar 2010
Posts: 231
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From: Lakeland
I think I have some exhaust leaks in my 300 and was considering doing a SeaFoam treatment to try and locate some of the leaks. I noticed the last time I did it there was quite a bit of smoke that was coming from more than the exhaust end. I think maybe doing a treatment and then looking through the engine bay and under the chassis might help pinpoint leaks. Just make sure you do it outside maybe even have a small fan blowing to help push it away.
