Adr4666

3.6L 2007
After three inspections (Audi dealer, Exhaust Specialist, Local Mechanic) I have been unable to get a definitive answer on an exhaust leak in the cabin. We experience the leak only when blower fan is on and often at idle/stop traffic conditions. Dealer suggested bad cats.Currently @ 105k.

No o2 sensor issue. checked ok at dealer.
No CEL.
No flex pipe leak (common)
No other leaks.
No soot.
No rough idle.
No hesitation.
No mpg issues.

Searched many threads and found other various opinions with little reliable causes such as EGR valve leak/bad, bad fuel injectors or seal, manifold crack, rear vent issues?

Any suggestions?

D3Audi

So the dealer can't figure it out at all? That's strange how it's coming through the vents. So do you ever feel dizzy from the fumes. Are you sure it's exhaust?

j4g3d

I randomly get this on my mk5 golf.

Its very odd and doesn't occur all the time.

Adr4666

Went to local garage this weekend and found front differential seal leaking after mechnanic permitted me to look with him when car was up on the lift.
It appears to be spinning differential oil on to the hot exhaust so we are going to replace this seal. Put nose close to this area and felt like fume smell in car was of same type.

This also makes sense since the fumes only exist after the car is driven and has come up to temperature.

I'm going back to the dealer to get my diagnostic fee credit back since this leak would have been apparent if they looked under the vehicle.

I love the car but despise my local dealer. They have been terrible over the past 7 years.

I will update this thread after repair is complete and fumes no longer exists.

flynavy

[QUOTE=Adr4666;24925313]Went to local garage this weekend and found front differential seal leaking after mechnanic permitted me to look with him when car was up on the lift.)

in my case I always let the engine idle for a minute or 2 before shutting it down and I got a whiff of burning oil every time. The right cam cover seal would leak out a little bit of oil and it would burn on the exhaust. I only found it after having a friend shut the car down while I looked at the engine. seal replaced problem solved....I still miss that car!

Adr4666

Got the car back and the exhaust fume still smells when the fresh air is on. Recirc kills the smell.
I wish I could find a competent mechanic who could help me as I'm at wits end. I still have a feeling something is being missed.

Adr4666

Went out and bought a CO detector with a wand.
Checked interior vents and detected.
Tracked entire exhaust and detected CO right at manifold/converter joint. Took car to shop to strip off cover and dismantle and found crack in cat conv pipe about 2" long parallel to weld at manifold flange.
Going to MIG weld and re-use cat as the cost $1k each from Audi.
Thought about aftermarket new replacement but was unsure of compliance and CEL issues reported in other threads.
Welding is not the best solution it is most efficient for my vehicle age/miles.
I will update when job is complete.