Heavy exhaust Fumes in cabin w/ window down?

[MrFairlady]

Ok so I'm Driving my Nissan a tad more lately and With a Kid on the way (highly doubt She will ride in this car) but damn...All of a sudden Theres a Ton Of exhaust Fumes in the cabin if the window is down or somewhat Cracked open.

:::::Run down on the cars exhaust is a basic 3" Dp,test pipe and Basic canister exhaust.All Gaskets Used at the flanges.

Now,This car was originally gonna be a Track only car so all the Sound deadening is Gone (use to be Gutted & no rear trim/carpet but thats all about back including carpet),and I do remember removing the rear cabin pressure flap near the tail lights/rear bumper area. I'm wondering if thats it?Still No trunk area flooring in the very back.

windows Up The smell is fine and Not a problem.This is not my 1st S13 nor is it my 1st Modded car (test pipes etc etc).
Any ideas other than an Exhaust leak ,Which I'm sure Its not?
My Last Hatch did not have this problem.

any ideas how to test for an Exhaust Leak.? Smoke machine make it Show Up if it is??? Should I maybe run a High flow cat or something?

[r20crazy]

check all the gasket areas in the exhaust. I blow out one of the cat gaskets every few hundred miles and get the same issue. start at the engine bay, start the car and have a feel around the joints. if you dont mind a tiny mess, baby powder and a makeup brush does same as the smoke trick.

[howyfeltersnatch]

i have this problem too. it could be you are missing a rubber grommet somewhere in your trunk area. im missing all of mine. and no exhaust leaks.

[macross]

I have this problem too, and still haven't figured it out, but from what i gather, you're creating a vacuum inside the car when the windows are down or cracked and exhaust is entering the vehicle from somewhere in the rear. My car is totally fine with the windows up, but it sucks when they're down. I'm going to investigate my taillight gaskets next.

[howyfeltersnatch]

I have this problem too, and still haven't figured it out, but from what i gather, you're creating a vacuum inside the car when the windows are down or cracked and exhaust is entering the vehicle from somewhere in the rear. My car is totally fine with the windows up, but it sucks when they're down. I'm going to investigate my taillight gaskets next.

this

and if you have a hatch check that seal too.

[tr0n9h]

I have a s14 and i have the exact same problems. only smell when window crack down. I have a feeling it has to do with the seal in the trunk. you should check that.because when it rain water leak into my trunk. I will try to change all the seal and update if it work.

I also check every single gasket starting from the manifold and back. So i know its not the gasket for sure. only other solution is the trunk.

I also have full interiors as well.

[MrFairlady]

All body Plugs in the rear are There.
I do know the cabin Equalizer Box is Out...and it Sits right near the exhaust kinda.
I do know that My Kouki Tails are not Sealed up With everything they came with but I do not remember this being a problem with my other Hatch with Kouki tails and Same Exhaust Setup.

got a New Flat Style Downpipe to install so I'll check all that soon.The Exhaust is New so the gaskets Are New also.
Still need a Backseat too.

[godrifttoday]

What is " cabin Equalizer Box"???? Any pics

[MrFairlady]

Its a Black box that has a flap inside and Mounts In the REAR 1/4 panels way down near the rear bumper Bolts on the side are.I found all Types of shit way down in there too.Its a black hole.

The Flap Pop's open when the Doors shut to Equalize pressure in the cabin.Kinda like a Sun roof popping open when you shut the door.
I removed Them when I painted the Inside of the cabin and don't remember putting them back.

My car does not have a sunroof...and The doors really don't shut that well.I have to close them hard...But thats besides the point.

[Socalgal]

Sorry to bump such an old thread but I've tried everything and searched for days and not found a solution. My car has full interior, perfect exhaust that extends plenty far out the bumper, and the vent box in the trunk people have mentioned is there and intact.

There has to be something we're missing here.

Has anyone actually fixed this issue?

My girlfriend can't even ride in the car anymore she gets so sick.

[Croustibat]

Air can also enter by the gearbox stick hole.

[jr_ss]

Air can also enter by the gearbox stick hole.

Tis true, however less likely. I'd check those boots for rips however, can't hurt.

[Socalgal]

I figured I'd give a rundown as well to give others with this problem some starting points and to tell what I've down.

My car is not a track car and every bit of the interior (both cabin and trunk).
I have all the rubber boots and the leather shifter boot.
I have no open holes in my firewall.
Full working hvac system.
I made sure the exhaust tip is far beyond the end of the bumper.
I had my super expensive wisesquare/berman exhaust mani at a machine shop with my elbow and d/p to have all the flanges flattened and replaced all gaskets for these areas.
I very closely examed the vent box and flap in the trunk(the pressure thing Mrfairlady mentioned and it's perfect.
I redid the piece of rubber between the back of the hood an the cowl vents.

My car is freshly painted and I'm thinking they may not have sealed the tails but there is a lot of monoxide making its way in when any window is open so I have a hard Time believing that's the issue.

Plan for next fun greasy work time will be to reinspect (for a third time) my test pipe gaskets and see what the mexican'ts did to seal my tails.

[jr_ss]

Are your outside air vents for the HVAC open? You could be pulling something from your engine bay in.

[roboticnissan]

Its definitely weather seals

[fliprayzin240sx]

Exhaust manifold leaking and fumes getting sucked in by the HVAC?

[Socalgal]

I may have actually made some headway with this fellas.

Thanks for all the ideas and I'll address these first.

My exhaust manifold is a very high end jdm unit made by wisesquare. It's extremely thick, gusseted everywhere, and was just re-machined at a good machine shop to confirm the flanges weren't warped. While they were at it I had the elbow and downpipe flanges machined and my hks turbo exhaust housing checked. Everything has new gaskets, studs, and nuts and has been triple checked by myself and a few trusted shops and I'm sure all that stuff is good right now. The best way I know to check is with a stethoscope with a metal end. We've also confirmed to the best of our abilities that there is no cracks as well.

Jr__Ss- The hvac intake ducts are on the cowl correct? I would assume they are open when using the heat or ac without the recirculating function on but again there is no exhaust leak in the engine bay to be pushed in there and there is also a pretty new seal in-between the hood's backside and plastic cowl. I also had that all apart lately looking for a ring I lost when doing the exhaust gaskets and everything is mint. On top of all this if the windows are up I get no fumes with any mode threw the vents in the car.*

I know all my transmission area boots are intact but I took that area apart again and the metal Both of the chassis and the ring that holds the boot to it were not perfect. I spent quite a while finessing things back to perfect and reassembled yesterday. I'm not sure this changed anything but it was something to do.

The cabin pressure equalizer box snaps in at the top and has two bolts that hold the bottom. The top was not snapped in and it was kinda hanging quite far out. I had taken the box out to do a closer inspection of the flaps and when reinstalling I heard the top snap into place and it all makes since now. I'm sure I'm not the first person to think that was a very convenient place for antifreeze and oil lol. All my fault.

Test rides went well last night. It used to be that the second I cracked any window or sunroof you'd get the faint smell of exhaust and I'd start yawning within a min and feeling what I've come to associate with monoxide.

I went like 25 highway miles trying all the different windows and hvac controls last night and no yawning.

Also the way air moves threw out the car with windows opened seems a lot less violent at highway speeds.

I think the aerodynamics of this vehicle (or pretty much any for that matter) might allow air and therefore a bit of the exhaust to be swirled, or sucked back under the bumper and with that box not able to do its job as a one way valve (essentially) it could've been sucked back in there.

I've not had a chance to put many miles on it yet but this definitely helped if not fixed it all together. My tail lights also do not seem to have any of the sealant around them so that's next.

[ghoti]

I know a friend's car does this its a leak at the test pipe I think.
Always remember to roll windows up on the highway or after a smoke show.

[Lunghz]

check the lines that go to the fuel filter(top and bottom), one might have a slit in it and it could just be the leaking gas that your smelling, this happened to a buddy of mine, hope it solves your problem!

[Vetal]

I started having exhaust fumes in the cabin recently. Checking rear of the car, I found that quarter panel where vent box sits has rusted out and so air from outside is free to enter the cabin, bypassing the vent box. Haven't restored the quarter panel yet so can't be 100% sure