Exhaust gases in a 2+2 with windows open

[Marcusu]

Hi all,
I’ve been doing some tests in my Series 3 2+2 with a CO meter to find out where exhaust gases are coming into the cabin.
With windows and quarter lights closed, CO meter shows 0.
With either drivers or passenger side windows down, or with both windows down, CO meter goes up to around 15ppm.
With both windows down and quarter lights open, meter shows 0.
With both windows up and quarter lights open, meter starts registering again.

I’m surprised that driving with just the window/s open could draw in exhaust gases. I’ve had an MGB GT and never had that problem.
In the 2+2 is it an issue with the shape of the car, lower air pressure in the cabin and the pattern of airflow sucking gases back into the cabin with the windows open?

For the next test, I’m thinking of blocking off the vent in the hatch and seeing if that makes a difference.
If not, I might have to look if there are any gaps/holes around the rear lights and valance area.
Cheers,
Marcus

[paydase]

Interesting testing.
Fumes in the cockpit are a recurring issue in classic cars, be it due to the bad sealings, aerodynamics, etc.
In the E-Type, there are also plenty of holes everywhere, especially in the boot area, and the tail shape favours exhaust fumes sucking, FHC, OTS or 2+2.
Looking fwd for advice of others.

[chrisfell]

Exhaust fumes are unlikely to enter through the drivers door window or passengers. Air rushing past the door will be at a lower pressure than inside the cabin - basic physics. What is more likely is that air venting through the open window allows more air to enter the cabin through intentional or unintentional gaps. I'd start looking for exhaust leaks under the bonnet and working backwards and then look for gaps in the bulkhead and gaps around the transmission tunnel area.

My car has multiple gaps especially around the gearbox area, but no exhaust fumes in the cabin as the system is fully tight until the tip of the tail pipes. I do get hot oil smell in the cabin but no exhaust.

[DWW]

I was going also about to suggest checking for exhaust leaks under the bonnet or under the car front.

[Marcusu]

Thanks for the replies all.
I will check the exhaust system front to back for leaks with my CO meter and see what I find.
Will also check under the bonnet.
Cheers, Marcus

[Marcusu]

I did a check under the bonnet and found the CO meter registering very high when placed next to the right hand side of the engine block. Left side is registering 0.
Seems I might have an issue with the right side exhaust manifold, either a leaking gasket or crack in the manifold.
Cheers,
Marcus.