I first noticed this a few weeks ago after filling up my tank. I exited the car and was going to take a walk with my girlfriend when we both noticed a really strong smell of gasoline coming from the driver's side rear wheel well. The gas fill up is on the passenger side and there was no spilled gas and no odor over there. It smelled really strong for a few days but as I drove and the tank became less full the smell finally disappeared for the most part. Since then, every time I fill up the gas tank it again smells like gas really strong on the rear of the driver's side. In doing research on the web, I've come across numerous people with he same issue. In fact, Mercedes offered an extended warranty for E class and S class vehicles for an extra 15 years after a class action lawsuit was filed for cars with this problem. I called Mercedes and explained the situation and basically they told me to go screw myself! He said that if I was a loyal customer they would consider that in their decision. I told him that this sure was a lousy way to create loyal customers considering that my problem is identical to the E class and S class issue with the fuel smells after fill up. I just wish Mercedes would do something since they know this an issue with many owners of CLK 500 class autos.

I had the hydraulic pump replaced on my CLK500 Cabriolet. The dealer's mechanic had to remove some trunk lining to work on the top mechanism. One week later, I filled up the gas tank and began to smell gas fumes when I left it parked in my garage. At first, I thought it might be coming from the gas can caps being loose or my lawn equipment. The smell disappeared soon after. I filled the tank again and the smell returned. A search of the internet revealed that this is a known problem. I would like to join any class action suit that has begun or that will go forward once enough complaints have been made. I contacted the dealer but have not had a reply as yet. If the hydraulic pump was an indication, I'm betting the dealer won't respond positively. That hydraulic unit is the second one to be replaced and I forgot to ask for the old part afterwards. I'm not certain now that he didn't replace the first one that was still in warranty and then said it was a different unit. It's become a trust issue now.

Update from Jan 28, 2017: Problem was with the seal for the gas sending unit. The dealer recommended that both units be replaced at a cost of $1500. I refused and took the car to another repair shop. The mechanic replaced the seal at a cost of $163, parts and labor. The cost of the seal was $24.