A/C Air Smelling Burned Diesel
 

My 2009 E-320 Diesel when stopped on traffic light with air conditioning running in ventilation only (only air from outside) the incoming air come with a smell of burned diesel. Even with no cars stopped in front of my car the incoming air will have the same smell. When driving I don't have this problem, certainly because the car is in movement, I don't have this problem.
Should I use a carbon activated filter? Is this issue from somewhere in the car?
As I bought this car not long ago I don't know what kind of filter this car have installed.
Anyway your suggestion will be appreciated.

I wouldn't expect you to be able to smell the exhaust with the HVAC in fresh-air mode unless you were positioned in such a way that the wind was blowing the exhaust back up under the car while you sat motionless.

It's possible that you have an exhaust leak somewhere up front and what you're smelling is the exhaust fumes that aren't making it to the tailpipe.

Does yours have a plastic pipe across the top of the air cleaner which carries exhaust? In my 300SD I smell exhaust at a stop and know that that pipe has slipped out of the rubber connector. Of course mine is a 1981 so I have no idea how MB might changed things.

On my 1982 300 SD I have the same problem but I noticed that this smelling come from this pipe that you are talking about and also from the engine air filter. As my 300 SD have a lot of blow back due the very old engine this smell is also from a blow back under the engine hood.
Anyway your reply was very good.
Thanks

Your suggestion makes a lot of sense. As the air intake to the cabin is from that surrounding area, it can be some leaking from the exhaust system close to the air intake. I will check that area and see if something is wrong there.
I had a similar issue on my 1982 300 SD but it was from a breadth rubber hose leaking around the engine air filter and this smell was sucked by the A/C blower.

Check all the bolted exhaust connections near the firewall. I've seen this happen several times.........

Does the carbon activated air filter help to eliminate outside odor (fumes from traffic, and others) to get into the cabin ?

You shouldn't be smelling exhaust in the car. You should find and fix the problem first.

Carbon filters can help resist the "musty" smell that some A/C's develop over time, but don't count on it to filter out odors from outside air. There's not enough carbon in the filter to absorb anything meaningful from the quantity of air moved by the fan. You can also expect a reduction in airflow since the filter is already technically partially "clogged" with the carbon dust. If you choose to run one of these types of filters, change them every 6 months if you use the outside air option frequently.

do you mean fresh evaporating diesel smell, or exhaust gas smell that is way potent?

It is more exactly like a smell of old lubricant oil heated by the hot engine block. Like I mentioned in another reply, my old 300 SD has a lot of blow back from an old engine and this blow back have a typical smell of burned oil.
When I stop on traffic lights with my A/C system running in ventilation only I get this typical smell inside the cabin. It is not as a smell of exhaust system but as a smell of heated lube oil.
I had no chance yet to verify what is around the A/C air filter.
Was my explanation enough?
When I asked about the carbon filter I do not mean that I want the filter to solve that problem but to learn better about the carbon activated filters.
Thanks

Now we're getting somewhere. The smell of burnt oil is different from the smell of exhaust. It's entirely possible you have an oil leak somewhere and you're smelling the hot oil on the block. Would be worth your time to go peeking under and around the engine with a strong flashlight and see if you've got some oil leaking somewhere. Under-hood oil leaks that get hot enough WILL cause the smell to come in through the fresh-air intake since it's right there at the hood.

Yes, it is exactly what you are saying. That is the smell that I am getting in my cabin. Thanks for your help.

It is well worth your time to check for oil leaks. The OM642 engine is known to form leaks at the oil cooler and various other places. If you have a leak starting up, that would certainly explain the smell of cooked oil in the cabin. If you do find an oil leak, you may want to start a new thread for better help tracking it down and finding out how to resolve it.

I have heard about oil leakage on OM 642. I have the Carfax for this particular car where I found this report: 132891 Miles- Crankshaft oil seal replaced, Intercooler checked. This car has now 153 K miles.
Also I found feel drops of oil on the floor from the passenger side of this car.
Can this drops come from intercooler?

In my opinion it's not from the intercooler,
Give it a a really good look around like previous post, but on a cold block and then again on a hot block.
Look for darker spots or "follow your nose"