My experience corroborated with the theory that it could be bad batch of gas which leads to the fart smell.
I won't blame it on anything else cause for us recent new car owners - nothing to get worried about. Early days in engine break-in still.

 

I have been smelling this funky odor in my Glk 2010 20M miles. I took it to the dealership and they flushed my whole A/C system and we even put in a new Cabin Filter. I took it home and the smell was still there, my buddy noticed the smell was coming thru the vents only when I first started or turned on my windshield wipers, we popped the hood and smelled the odor pretty bad...guess what it was coming out of my washer tank!!!! It really smelled...I took it back to Mercedes and they took the tank out and flushed it and replaced my fluid with mercedes w/w fluid.. I live in Florida and have been using the 303 brand tablets that you drop in and make the cleaner.. Mercedes says this is what caused the smell...our tanks or nozzles are heated and the tablets were not compatible...I have been using them for a year with no problems.... they said only buy their brand washer solvent..smell is gone..was it the tablets or?????

 

did you ever tried running the heater of the car in full power for at least 20-30 minutes? that might dry off your duct work and get rid of the smell. Always run the heater for a few minutes whenever you use your AC to dry out the moisture inside your ducts.

 

Isn't that sort of counter-productive? Never had to do that in the many non-luxury vehicles I've owned.

 

Apparently the rotten egg smell is common among some vehicles and some gasoline vendors. I consulted my Corvette Owner friend. He said he notices the smell after work when he walks behind his car in the garage. His Vette has 24,000 miles on it so the "goes away with age" may not apply to all cars.
As for drying out the duct work after use, SUPPOSEDLY, the 2012 model GLKs have a dry down function after use. The fan comes on an hour after use and runs for 30 minutes. On an as needed basis based on internal humidity. I have no idea how to verify this since the fan shuts off if you open the doors.
In summary. Live with the rotten egg smell if you have it. Try various gasoline vendors to see if some brands are more pleasant than others.

Nor I in all of my luxury (Volvo) and non-luxury (Trooper II & GM) vehicles. Thank M-B for finally coming up with a solution for the musty-mildew-moldy problem in the HVAC system after several years of loud complaints from owners of various models. Better late than never.
Blue cloud of smoke: Waiting for that to go away.

Wayne

 

I just posted this on another thread, my brother is mechanic at Ford.



Ok, so far this has fixed the problem, park your car on a incline with the engine facing downward, aka back in to your garage. The issue is all the water in the ac may not be draining out overnight causing the mildew smell at startup. If your smell is really intense go ahead and change the cabin air filter as well also spray some Lysol in there. That was my original temp fix which lasts about 3 months. The smell shouldn't come back if your consistently parking on a engine downward incline you should smell better results in 2 days.

 

I had a similar odor on my '08 E350 and traced it to the windshield washer fluid reservoir, which sits right underneath the cabin airfilter and intake box.

Easy test - pop open the cap on the fill and take a whiff.

Flushed with water a number of times and refilled, using distilled water and some Rain-X washer concentrate - no problems since.

 

I had the same problem recently. For a more permanent fix return the GLK to your dealer's service department and ask them to activate the "Run-Dry" feature. Once activated the GLK's blower will turn on and run for 30 minutes to dry the a/c condenser after the car has been turned off and locked. Also to get rid of the smell use Frigi-Fresh (also available at your MB dealer), not Lysol. Frigi-Fresh is designed for use in automotive applications. Lysol contains harsh chemicals that can corrode parts of your car's heating and cooling systems.