I have an 04 A6 S-Line with 40k. There has been a great deal of work done to the car despite the low mileage. Most recently, the turbos were replaced. I've noticed a strong odor entering the cabin when the heater first starts working. After about 5 minutes, the odor goes away but it remains strong outside of the car. In fact, my whole garage starts to stink. It seems to do it only on cold days when the heater is running. I've been checking my fluids but all looks well. No puddles are appearing under the car and I searched under the hood and didn't find any apparent leaks. I can't really explain the odor other than it smells like something burning or hot but not necessarily like radiator fluid or oil. Any ideas on what it might be? Car is still under CPO but not sure I can deal with the hastle of another issue...

 

The only thing i can think of is a valve cover or cam adjuster seal leak.
When was the last time you changed your cabin filter? They need to be changed every 15k.

 

Would cold weather impact valve or cam adjuster? It seems to occur only on days that are below freezing. Not sure if the cabin filter has been changed or not but good point. It's had all the scheduled maintenance so I'd assume it has but don't know for a fact. Would the odor from dirty cabin filter be detectable from outside the car?

 

If you have something rotting in the filter assembly like leaves yeah you would smell it, but that would give you more of a musty smell.
What i think what happens is the cam adjuster seal hardens under cold weather and tends to shrink (its rubber) and lets oil past it leaking onto the exhaust, once the seal heats up it expands and closes the gap. My S4 2.7T used to do that almost all the time when i parked it outside. Even after i changed the seals.

 

Is in an AC smell or oil smell? I think there were many people complaining about the musty AC smell. Here is a TSB on a newer car, with instruction. Stuff that they use in the the TSB is simple air cleaner such as this.

http://www.maryellenproducts.com/atmosklear

Also be sure to change your cabin air filter as well while at it. More description on the smell would be nice.

 

I think you're on to something wiht the cam seal. It does smell like burnt oil and only occurs on cold days. Is this something that would be worth me taking it to the dealership for or should I live with it since it sounds typical?

 

Well the dealer has something thats called "blue" which is a sealant that we use with the seal that only dries in absence of oxygen. So we coat the half moon seal with it when installing the new seal which helps keep it from leaking when its cold outside. But mine started leaking about a year after i replaced the seal, however the leak was much less than it was and i hardly ever smell any oil burning. If its under CPO warranty what they are gonna do is replace the valve cover gaskets first, then wait for you to come back if there is still a problem, then they will replace the cam adjuster seal. Techs used to flat rate the seals under warranty to the tune of 7+ hours which only took them 1 hour so audi got a little pissed at us for taking advantage of them. So they only let us replace the valve cover gasket first.

 

Thanks for the advice :-)

 

just to throw this out there, my dad had the same problem with his subaru. turns out there was a mouse somewhere in the whole engine area :O, it died and started to rot, and it did only smell on cold days.... you'd think it'd be worse on hot days