Exhaust leak in the cabin ?

[deschodt]

Lately I've been smelling some funk in the cabin at speed. Wife and kids thought nothing of it when asked to sniff it out, but I have the nose of a blood hound and I could smell something "exhausty".

 

So I borrowed a CO tester from my house, one with a display...  Drove around town at low speeds, 0 - nothing... 

Drove on the freeway, windows closed, a-ha  20 PPM of CO inside.... Cracked a window - went up to 35 PPM !   I'm not crazy !  

I don't quite get why in town there is a zero reading but I imagine some aero effect requiring a certain speed to suck in gases... Cracking a window open probably creates a vacuum and makes it even worse... 

 

I plugged up all the firewall holes I could find, there was a bad gasket around the fuel line, fixed, a hole next to it, plugged... Heater is disabled, not even connected... I'm struggling with where it could come from... Shifter ? That has a tight boot...Trunk ?   How do you go about testing this ? I can put a smoke machine in the engine compartment to find more firewall holes, but nothing changed here, it's been porous for years and never smelled.. Can one track down exhaust leaks specifically ? How ? Adding something to the oil to make the exhaust "dirtier" ?  I'll take it in if I cannot figure this out, seems dangerous despite not being enough CO to trigger the detector's alarm - but enough to register... The exhaust line is relatively new (9 years) and looking mint but the manifold looks like it came from a Uboot. Then again nothing at low speeds... Odd...  Opinions/advice welcome ! Thx ! 

Edited November 29, 2016 by deschodt

[jimk]

You are creating a low cabin pressure at speed with the window open.  Air passing by the outside of the car creates low pressure along the window.  Seems like it is sucking exhaust in from the rear vents/trunk.

[deschodt]

I've just found the trunk seal discussion. Sure enough the car was repainted and the trunk seal reinstalled, so I'll start there. maybe smoke the trunk, sound sbetter than locking myself inside it...  I'm fuzzy on the extra foam tape you guys use to seal it better, anyone got a picture of what they did / where exactly they installed that extra layer ?  Pretty sure you nailed it....

 

Are there obvious openings from the trunk to the cabin I can plug ? I sense a smoke machine in my immediate future...

Edited November 29, 2016 by deschodt

[landon]

41 minutes ago, deschodt said:

I've just found the trunk seal discussion. Sure enough the car was repainted and the trunk seal reinstalled, so I'll start there. maybe smoke the trunk, sound sbetter than locking myself inside it...  I'm fuzzy on the extra foam tape you guys use to seal it better, anyone got a picture of what they did / where exactly they installed that extra layer ?  Pretty sure you nailed it....

 

Are there obvious openings from the trunk to the cabin I can plug ? I sense a smoke machine in my immediate future...

Speaker holes, fuel lines. The lip of the rear panel can be easily bent upwards to create a better seal as long the rubber seal is in good shape.

[71bmr02]

Best place to start is the trunk seal, after that try plumbers/electricians putty found at big box home improvement stores to seal any holes in the trunk area that give access to driver/pass compartment.  The putty is easy to work with doesnt shrink fills large and small holes and cheap.  use silicone around speaker holes and a large enough plastic storage container to cover the speaker hole, i used a stack of books and paper wedges to hold the storage container up against the speaker shelf till the silicone set.  there are two holes in the rear seat bulkhead at corner where bulkhead meets wheel arch can be plugged with putty.  also found other holes PO had drilled for whatever reason and plugged them.  Also hole where fuel lines go thru bulkhead.

 

Gale H

 

 

[PaulTWinterton]

Unless you have a broken exhaust manifold (loud), or downpipe (loud), or loose connections at the mufflers (loud), your problem is at the trunk.

 

If all components are correct you should not have to modify the car. Proper seals and "elephant trunk" pieces should be in place.  The exhaust pipe should extend to outer edge of rear bumper, not under the car.

 

A great example of this problem is driving a hatchback vehicle with the hatchback open.  STINKY!!!

 

 

[Mike Self]

1 hour ago, PaulTWinterton said:

Proper seals and "elephant trunk" pieces should be in place. 

This is referring to the seals that surround the heater plenum chamber:  that's the well under the hood louvers that serve as an air intake for the heater/vents.  With leaky seals there, exhausty-smelling air can be forced into the cabin.  Also check the foam seal under your shift boot.  If there are fumes underneath the car, they can creep into the passenger cabin at that point, especially if the rubber boot is split, and/or if you have a long console, where its oblong boot isn't fastened directly to the floor.

 

But rule out the trunk first--that's usually the source of cabin fumes.  

 

mike

[PaulTWinterton]

43 minutes ago, mike said:

This is referring to the seals that surround the heater plenum chamber:  that's the well under the hood louvers that serve as an air intake for the heater/vents.  With leaky seals there, exhausty-smelling air can be forced into the cabin.  Also check the foam seal under your shift boot.  If there are fumes underneath the car, they can creep into the passenger cabin at that point, especially if the rubber boot is split, and/or if you have a long console, where its oblong boot isn't fastened directly to the floor.

 

But rule out the trunk first--that's usually the source of cabin fumes.  

 

mike

 

Oh!  Maybe I have my terminology wrong.  I refer to the 'elephant trunks" as the plastic pieces hidden in the upper forward corners of the trunk.

 

AFAIK, they are a component of the re-cycling air in the cabin.  The Tii does not use them as the electric fuel pump and differences in fuel delivery negates the use of the elephant trunks.  Please, someone with better knowledge step in.

 

[02Les]

27 minutes ago, PaulTWinterton said:

 

Oh!  Maybe I have my terminology wrong.  I refer to the 'elephant trunks" as the plastic pieces hidden in the upper forward corners of the trunk.

 

AFAIK, they are a component of the re-cycling air in the cabin.  The Tii does not use them as the electric fuel pump and differences in fuel delivery negates the use of the elephant trunks.  Please, someone with better knowledge step in.

 

The item you ringed is not used if your car has a sunroof. If it does have a sunroof, then item 8 is used to plug the whole you "arrowed" in the second pic.

[peterschop]

The first thing I would check is where the shift lever sticks through the floor as Mike mentioned. There should be a doughnut shaped foam gasket that seals the fumes from entering the cabin. 

[PaulTWinterton]

2 hours ago, 02Les said:

The item you ringed is not used if your car has a sunroof. If it does have a sunroof, then item 8 is used to plug the whole you "arrowed" in the second pic.

 

Ahhh, I get it.  I have a sunroof and the holes are capped.

[silasmoon]

Do they still make those plugs for those holes? I have one, but sorely need another. 

[John_in_VA]

1 hour ago, silasmoon said:

Do they still make those plugs for those holes? I have one, but sorely need another. 

I don't think so.  They're getting pricey on the used market here.

[dave-r]

OP,
When I installed new seals for trunk (not factory BMW, but URO) I had same exact issue, even with all the adjustment in the world there was no way it was ever going to seal around the sides especially. I would take a thin piece of sheet metal and sweep it around and the gaps were large. I ended up, due to wanting to drive my car and dumping countless amounts of money in the car, did not want to dump another amount on new factory seal, just getting some maybe 3/4" wide by 3/16" foam sealant tape and placing it around sealing surface of trunk lid. Fixed issue for now, although I will be ordering new factory seal soon. Good luck!!

Sent from my SM-G920P using Tapatalk

[halboyles]

 

1 hour ago, silasmoon said:

Do they still make those plugs for those holes? I have one, but sorely need another. 

 

 

Yes they do!  Order two they're small.

 

https://www.wallothnesch.com/abdeckkappe-fuer-entlueftung-im-seitenteil-hinten-nur-bei-ssd-wird-2x-pro-auto-benoetigt-51-45-08.html