Cabin fumes

[PhilC]

With the windows shut I have no engine/exhaust fumes in the cabin at all.

When I open the window, quarter light or main window I get fumes sucked in. I don’t know if they are coming through the firewall or from outside. Any suggestions please.

[jimk]

When a side window is open, the open window sucks air out of the car and any point at or near the rear of the cabin will suck in exhaust.  Openings around the rear backrest seat, thru vent over the rear window/vent ports at the trunk.  Unavoidable with a side window open.

[PhilC]

So an experiment is in order then. Tape up the rear window vent and the two little trunk vents and see if anything changes.

[Eissmann]

Been there. I found openings where fumes could enter by putting a bright light inside the closed trunk.  (with the car in a dark garage). With the rear seat out I could see light coming in from behind the bulkhead.  
I sealed those openings with butyl rubber strips.  I also eliminated the speaker holes under the rear window. 
I also found that my muffler was leaking. When I replaced it I made sure the tip stuck out beyond the back edge of my bumper. 

[mike472]

Look for openings in your firewall under the dash.  Frequently the speedo cable grommet is missing where it passes through the firewall into the engine compartment.  Also the three rubber seals in your engine compartment have to be in good shape.  The two short ones on either side of the engine compartment near the windshield and the long one that goes across the underside of the hood the comes to rest on the body right in front of those two short ones.  Once you open windows in the car you create a vacuum within the car sucking all those fumes from your engine compartment into the ventilation system.  I'd say that's the likely culprit.

[Son of Marty]

Also check the 3 duck bill drains in the heater plenum they can get stuck open when they don't clear the junk all the way out (pine needles) or they could be missing completely.

[John76]

Exhaust fumes? Gas fumes? Oil fumes?

Which one(s) are being sucked into the car?

Try to identify after following the above tips on sealing.

Gas fumes are usually a result of a leaky fuel tank or fuel lines.

[PhilC]

Thanks very much All. Very helpful advice.

It is exhaust/engine fumes, not gas (petrol).

No speedo cable so there could well be a hole there.

No drain tubes, one hole is blocked up so two to deal with.

Likely one or two other holes in the firewall to block up.

Exhaust does stick out slightly further than the rear bumper (actually illegal here in the UK) so that is off the list.

As above, I will test by blocking rear window vent and trunk vents.

Under bonnet rubber seals are ok as far as I can tell.

I will definitely use the bright light method to identify holes.

Will check for exhaust blow but pretty sure there isn’t one.

 

Edited April 8 by PhilC

[Vicleonardo1]

Phil, Let us know how it goes.

I would say that if you followed all the tips above, if your 02 ever ends up in the Thames, it will float out to sea. 😄

Cheers! 

[PhilC]

2 hours ago, Vicleonardo1 said:

Phil, Let us know how it goes.

I would say that if you followed all the tips above, if your 02 ever ends up in the Thames, it will float out to sea. 😄

Cheers! 

Will do. Need to make sure I can still breath with the windows shut 😄

[John76]

Phil,

Do you have the plastic tubes that connect the cabin flow-through vent (non-sunroof cars only) through the trunk to the outside?

If not, any exhaust fumes that enter into the trunk (boot) will find their way into the cabin through the vent above the rear window.

 

[PhilC]

On 4/9/2024 at 7:49 PM, John76 said:

Phil,

Do you have the plastic tubes that connect the cabin flow-through vent (non-sunroof cars only) through the trunk to the outside?

If not, any exhaust fumes that enter into the trunk (boot) will find their way into the cabin through the vent above the rear window.

 

I do have these. I also have holes (not rusty ones) in the spare wheel well. I shall block these up too 👍

[Tdh]

On 4/8/2024 at 11:35 AM, jimk said:

When a side window is open, the open window sucks air out of the car and any point at or near the rear of the cabin will suck in exhaust.  Openings around the rear backrest seat, thru vent over the rear window/vent ports at the trunk.  Unavoidable with a side window open.

So I understand, are you saying that there is no way to avoid exhaust fumes in the cabin with a side window rolled down because exhaust is gonna get sucked into the cabin through the rear window vent? How would you stop this from happening?

 

Edit: Never mind. I thought it through and get what you are saying now. I’d had few Old Fashioned’s when I read the post last night. 

Edited April 11 by Tdh

[Mike Self]

In summary...exhaust fumes find their way into the passenger compartment via the following ways:

1. poor/missing/loose trunk lid perimeter seal
2. speaker holes cut in the package shelf
3. missing sponge rubber plugs behind the back seat where the package shelf, C pillar quarter panel reinforcement and trunk/pax compartment separator all meet
4. holes in the "real"--i.e. the steel trunk floor/spare tire well

Engine fumes get into the passenger compartment via

1. poor perimeter seals around the heater plenum chamber (heater air intake)
2. missing or rotted "duck bills/elephant trunks"--plenum chamber drains
3. unplugged holes in the firewall or missing/rotted grommets around cables and wires that pass through the firewall (hood release is the largest).

That's all I can think of/gather from above...

 

mike