CO in Cabin

[JohnnyO]

I'm getting carbon monoxide entering the D90 passenger cabin.  This is a 300 Tdi that I've had for a couple of months.  It was occurring with the hard top on and it's the same now that the soft top is installed.  The exhaust system is new and I've had it checked for leaks by two different muffler shops.  I discovered a significant improvement by closing off the heater vents with duct tape.  This would lead me to think there are two issues: there's some kind of CO blow-by happening under the hood, and the heater is pulling air from the engine bay instead of fresh air from the outside.  Any ideas for next steps in troubleshooting?

[Trevor]

Exhaust gasket leak perhaps? But for that to be a factor you would need to have air moving freely into the cab somehow, perhaps via the heater as you noted.

[Red90]

Is this RHD (putting the heater on the exhaust side) ?  My first guess for a leak would be the manifold where the two outside pipes join the turbo.  It is just a loose fit and they are known to leak.  This could be taken apart and muffler cement added to the joints.

The air intake for the heater has a foam seal where it joins the fan.  Have a look to see if that may be leaking.  See item 12 in the diagram below.  Also check that the drain (item 13) is not stuck open.

http://www.allbrit.de/UNI.cfm?PAGE=760644&SPRACHE=EN

[binch]

I was thinking the samething...check the joints from the manifold to the turbo and down pipes and see if anything is leaking past a loose joint there.   Are there any bungs missing on the firewill.    And since the air supply to the heater should come from the fender top check to see all the seals are intact from the fender top back to the firewall itself.

I'm assuming you installed the bottom door seal for the back door...yes?