Chasing exhaust smell in 240 cabin

[Jaymanbikes]

So I know exhaust smells the the cabin is an age old problem, there are tons of threads about it and I think I’ve read them all over the years.  
 

I restored a 72 and knew about the issue so I was careful to address any and all leak points I was aware of during restoration.  I replaced all the surge tank hoses, and all the grommets from the fire wall back to the hatch of the car.  I have ensured my tail light gaskets are good, my hatch gasket is perfectly sealed, the shifter boot is sealed etc.  I have the car running and driving/handling better than I ever thought it would.  When the windows are up, no smells but the minute I roll the window down I get exhaust.  I checked my entire exhaust system (which is all new) for leaks, he’ll I purposely made the carbs lean just to see if I was running rich and the smell is still there.  
 

The smell is bad enough that the first thing I do is change clothes when I get back home.  I’m just out of ideas as to what the hell is going on.  I’ve ridden in plenty of other 70-73’s that don’t pump out these smells so I know something is up.  
 

Any ideas you have, shoot ‘em my way. Pics just for the hell of it.  
 

Thanks!
 

 

[AZ-240z]

Enjoyed the pictures of your beautiful Z.  I’ll give you my take on the cause and possible fix of your fuel/exhaust smells.

I’ve done everything you did to seal all obvious sources of interior leaks.  To make all the changes in grommets,

weatherstripping, etc., I had removed all interior paneling and carpeting in the cargo deck area.  Upon close inspection

I found that the weld seams around the edges of the rear deck floor had some gaps showing daylight.  A little rope

calk fixed that and no more exhaust smells, window open or closed.

this may be obvious, but, when you open a window, this causes a Venturi effect which sucks out cabin air and sucks

in exhaust through leaks in the rear deck area, so the exhaust isn’t really coming in the open window.

Hope this helps.

Dan

 

 

 

[DatsunZGuy]

A couple of ideas:

1.  Get yourself a tube of ShinEtsu grease and apply a good amount around your hatch gasket. Keep the hatch open overnight to allow the grease to soak in and expand the rubber a bit.  This technique works well with leaky t-tops and may help your situation.  Then, take the car out for a run.

2.  It is hard to tell in the photograph, but it looks like you have a Fujitsubo Legalis R exhaust system installed.  As goofy as it sounds, I would try using about a foot length of PVC pipe (or similar) and attach it to each of your tailpipe tips and make the seal air tight with something like aluminum tape.  Drive around the block with the widows down and then up to see if the extension makes any difference in the fumes.

These suggestions may seem a bit unorthodox, but you have pretty much tried the all normal remedies.

[Jaymanbikes]

4 hours ago, DatsunZGuy said:

A couple of ideas:

1.  Get yourself a tube of ShinEtsu grease and apply a good amount around your hatch gasket. Keep the hatch open overnight to allow the grease to soak in and expand the rubber a bit.  This technique works well with leaky t-tops and may help your situation.  Then, take the car out for a run.

2.  It is hard to tell in the photograph, but it looks like you have a Fujitsubo Legalis R exhaust system installed.  As goofy as it sounds, I would try using about a foot length of PVC pipe (or similar) and attach it to each of your tailpipe tips and make the seal air tight with something like aluminum tape.  Drive around the block with the widows down and then up to see if the extension makes any difference in the fumes.

These suggestions may seem a bit unorthodox, but you have pretty much tried the all normal remedies.

It’s a Z Story Exhaust but I did think about putting a downward tip on the muffler to just see what happens.  (I actually now have a single outlet muffler, the dual muffler was just too loud) I did try a straight extension but it didn’t help.  After thinking it through I realized I wasn’t getting the exhaust away from the airflow, if anything I was just making it worse.

[Jaymanbikes]

5 hours ago, AZ-240z said:

Enjoyed the pictures of your beautiful Z.  I’ll give you my take on the cause and possible fix of your fuel/exhaust smells.

I’ve done everything you did to seal all obvious sources of interior leaks.  To make all the changes in grommets,

weatherstripping, etc., I had removed all interior paneling and carpeting in the cargo deck area.  Upon close inspection

I found that the weld seams around the edges of the rear deck floor had some gaps showing daylight.  A little rope

calk fixed that and no more exhaust smells, window open or closed.

this may be obvious, but, when you open a window, this causes a Venturi effect which sucks out cabin air and sucks

in exhaust through leaks in the rear deck area, so the exhaust isn’t really coming in the open window.

Hope this helps.

Dan

 

 

 

Yea I removed all my panels (multiple times). Looking for any gaps. I actually found a couple buried up where the rear portion of the quarters meets up with the rear panel.  I thought for sure that was it!  I sealed them up….same results.  I couldn’t see them from above but I slipped a flashlight down into them and I could see light!   Was totally bummed

[dutchzcarguy]

A simple test to see if your rear hatch seals are doing the job well is some small strips of paper between the rubber and the hatch door..  If you close the hatch and you can easely pull the paper out.. then you have a leak there! 😮

[Jaymanbikes]

1 hour ago, dutchzcarguy said:

A simple test to see if your rear hatch seals are doing the job well is some small strips of paper between the rubber and the hatch door..  If you close the hatch and you can easely pull the paper out.. then you have a leak there! 😮

Yep, tried that one.  That’s why I know it’s sealing. 

[madkaw]

Go buy a fog machine . I think I made a thread about this . Get your shop vac and tape seal around a window that is cracked open . Turn on the machine and get in the car with a flashlight . I suspect it the panel on the hatch . That vinyl panel needs to sealed with RTV is something . The low pressure will pull fumes through your hatch latch and around that panel . If you have had that panel off I bet that’s the source . The fog machine will tell all

And I’ve been driving around in a Z with a Z story exhaust - it’s not the exhaust system 

Edited February 16, 2023 by madkaw

[bartsscooterservice]

Hey it's part of a classic getting gassed 😂

 

 

Seriously though, I'd go with the above advice, I think it's coming from the rear, sucking it in, when you open up the windows.

[Jaymanbikes]

On 2/16/2023 at 10:00 AM, madkaw said:

Go buy a fog machine . I think I made a thread about this . Get your shop vac and tape seal around a window that is cracked open . Turn on the machine and get in the car with a flashlight . I suspect it the panel on the hatch . That vinyl panel needs to sealed with RTV is something . The low pressure will pull fumes through your hatch latch and around that panel . If you have had that panel off I bet that’s the source . The fog machine will tell all

And I’ve been driving around in a Z with a Z story exhaust - it’s not the exhaust system 

I did buy a fog machine, and did exactly what you mentioned.  The fog has a distinct smell and in time that smell did make its way into the cabin, however it was not apparent where it was coming from.  I’m going to try it again and see if I can determine where the leak is.  What’s interesting to me is, when I open a window, the exhaust smell is immediate, I would assume if it were a small leak it would take a bit of time for it to permeate the cabin.  As I said, will try again.

[87mj]

If it were me, I would get some seam sealer and remove the inner plastic panels and seal as far up the wheel arch as possible and along the back to the other side.  I would also check the antenna grommet hole and caulk that.   I would also remove the rear panel on the hatch and buy some of that over priced foam sound deadener (the name escapes me now).  Remove the adhesive only at the contact areas of the panel and stick that to the rear hatch.  Then any fumes making their way past the rear hatch gromets and rear hatch latch have no where else to go. Then put the hatch panel over the top of that. You will not be able to see the sound deadener.

Then if I still have fumes, I would know they are coming from the rear hatch or the taillights.  Then I would probably unbolt the rear hatch piston so the hatch would receive equal pressure on both sides against the weather strip (just as a test). Then if it goes away, you found the leak.  Please give us an update. 🙂 

[madkaw]

Not apparent because you couldn’t tell from what direction ? Was it coming from the rear hatch area ? Have you sealed that hatch panel ? It can be tough to tell . Usually if you don’t see it right away it will make it hard to determine exactly where it comes from