Hey gang,

I have a 2007, E350 with 43k miles, that is kept garaged. I purchased it with 40k miles on it and a clean bill of health from a dealership that performed an inspection. From the very first day of ownership I noticed my garage suddenly had a strange smell that was also found inside the car (even with windows rolled up!). The odor is somewhat sweet and oily... kind of like kerosene. Previously, I had a 1999 E320 in the same garage for a decade and I never noticed that smell until the morning after the first night the E350 was in my garage. This odor completely permeates the air in my 2 car garage. So, I’ve been researching this forum to see if any of you have the same complaint. I found several threads on this forum about exact same problem. I tried to look for commonalties in those threads, but there were few. Even worse, all the threads lacked any firsthand knowledge confirming a cause and all of the possibilities mentioned lacked scientific data to support their claims.

Here’s what can attest to based on what my nose detects.
1. When parked in the garage for 2-3 hours my whole garage stinks. When parked overnight in the garage the odor is much stronger.
2. It makes no difference if the car is park inside or outside the garage overnight. With the windows rolled up the interior of the car still stinks anytime it’s parked for a few hours or more.
3. The odor is occasionally noticeable when exiting the car after parking either inside or outside the garage.

Professionally, I am a firefighter and hazmat specialist. So, I decided to treat this odor like the typical “sick building” call where someone smelled something. I used a hazmat monitor and suggestions from other threads in the forum as to the possible causes. In the end I located the general area of the source.

Here’s how I did it.
I monitored my garage and found VOC levels (Volatile Organic Compounds) standing between 5 and 9 PPM (Parts Per Million). When I opened my car door I found up to 19 PPM, VOC in the interior. I monitored the interior of the car, specifically putting the inspiration inlet close to various materials (leather carpeting etc.) and in areas that were mentioned as possible cause. When I switched the fan on the air coming through the ventilation ducts was so clean it actually dropped my meter back to zero as long as I kept the inspiration inlet stuck in the vent. That rules out the cabin filter. With an odor so strong in my garage I quickly ruled out any causes located inside my car. Next I went to the Engine compartment and I found nothing. Same findings in the trunk, not even a 1/10 increase on the meter. Next I put the inspiration inlet between the weather stripping of each window. Mildew in those areas was listed as a possible cause. Again nothing. And, I let the meter inhale the weather stripping fabric around the door for about 5 minutes… nothing. I also did a 5 minute test around the gas cap to check the gasket and there was no increase in VOC readings. So far I have ruled out every possibility that has been offered as an explanation on this forum, except the sound proofing mat around the transmission (assuming that my car even has one). I couldn’t figure out how to find the mat much less get close to it. Then, I began going around the car slowly. I got a hit on my meter near the LEFT Rear tire. After checking out the entire perimeter I went back to the LEFT Rear tire. In photo #2 I got a maximum VOC reading of 287 PPM. In photo #3 I stuck the inspiration inlet into the small hole that the red arrow points to and I got a VOC reading of 434 PPM. In photo #4 I shoved the meter about halfway into the hole where the red arrow is pointing and I got a maximum VOC reading of 1422 PPM. To verify my results, I tested the opposite side of the car in the exact same locations. Not only did my meter not detect anything, there was a significant difference that my nose detected. It actually didn’t stink on that side of the car. There is definitely something in that area of the car that is capable of creating a nasty odor, that persists for long periods, or as best I can tell it persists forever unless it’s found and corrected and it has the ability to penetrate into the passenger cabin.

Below I have attached 4 photos.
Photo 1: MultiRea Plus (4 gas monitor with Photo Ionization Detector)
Photo 2: LEFT Rear tire
Photo 3: LEFT Rear under chassis (near jack placement location
Photo 4: LEFT Rear area behind LEFT Rear tire, in front of axel where the plastic cover plates leave a gap

Ok, I found the general area of the odor, but I lack expertise of the car’s construction to know what systems and components are located in that area of the car. This is where I need YOUR help. Before I start pulling those plastic undercarriage panels off to do some exploratory “sniffing” I would like to hear from those of you who have knowledge of the car’s construction, systems and components that are located in that area. I’m in no rush, so let’s get some replies in here and discuss where I should look next and what I might need to be looking for. Maybe we can get this problem solved and posted on here once and for all.

Best regards!

 

Your fuel pump and filter are above that plastic panel in front of the tire. Something is leaking slightly in there.

Maybe............

 

Thanks for that information! I want to believe it’s the fuel since there is a finite amount of things that are built or poured into a car. I really want to agree with you, but until I get some of those panels down and look farther, I hesitate to add “fuel to my list of possibilities. Here’s why

I got a huge VOC hit on my meter. The meter I used also has an “LEL” sensor. (LEL= Lower Explosive Limit) If in fact that odor was being produced by gasoline vapors it should have registered on the LEL sensor. I got zero readings on my LEL sensor. I’m not saying it isn’t gasoline… I know strange things can happen and yes gasoline will give off a "huge VOC hit" too.

Can you think of any other component or system that’s in that area of the car? I’m going to give this until next week before I start tearing it apart. Hopefully, more folks will have responded by then.

Tomorrow I am going to park the car for about 10 hours then sample the air inside the cabin with a PPBRea and a meter that’s called “GasID”. I'll report those results tomorrow night.

Hopefully, I can figure this out since there are others with the same problem.

 

Have you pulled up the carpeting and trim in the trunk, above that spot, to see if anything is in there?

I believe that cover under the car only has three torx screws holding it up. If in fact on you car, the fuel pump or some other component is above it, you should see signs of a leak once you remove the cover.

Or, does the smell remind you of overheated acid? Maybe your alternator is overcharging your battery, causing it to gas off. Not sure where the battery(s) is/are on your car, but the batteries usually have an overboard drain from the battery vent.

 

Definitely not overheated acid. The first monitor I used checks for Hydrogen Sulfide and there was none detected in my initial survey.


GasID monitor gave me a high percentage result of Benzene and Methane gases. As far as I know there is only 1 thing that is connected to a car that would give off this quantity of those gases. That's gasoline. Don't know where it's escaping from becasue it's not wetting the floor in my garage and the panels under the car are not wet. So, now that I have that figured out, what next?

I've seen some threads about gas tank seals going bad and leaking seals around clamps at the sending unit tubes. Anyone know more about this?

 

Did you unscrew the cover and inspect? You don't need to leak a whole bunch of gas to stink the place up. Put a <drop> in your kitchen and see your wife's reaction.

Does this car have airmatic suspension?

I looked up tsb's on your model year car, and saw none for the leaking fuel tank gaskets found on some older models,

 

waybomb:

No, I haven't pulled that cover off yet. I won't have an opportunity to do that until next week. Now that I've identified the gas I'm smelling, I feel confident I'll find a wet spot somewhere under there.

I'll get more info and some pics up on here next week after I ge the panel off.

Thans alot and special thanks for checking the tsb's for me.

 

Hope you have found your problem because I have a 2010 SLK350 that is only a year old and have an odor, mine smells like chemical or crayons. The dealer has detailed twice, shampoed the carpets, cleaned the ac ducts and ac coil and last month replaced all the carpets. The smell is a lot better but it still comes back after a few miles of driving. What else can be done. Thanks

 

Yes, I did find the problem. It was a hairline crack in the sensor unit that is mounted on top of the fuel pump assembly. That assembly is located in the fuel tank under the rear passenger seat, driver’s side. It’s really easy to access and work on. It was such a small leak the gas evaporated quickly leaving little trace to locate it.
I purchased a new pump assembly for $400. Before I installed it I did the following. I filled my car to the maximum possible and drove around tapping the brake to slosh the gas in the tank around. I had my brother in law sit in the back a and look for wet spots on the assembly. We found a hairline crack in the plastic welded seam where two pieces of plastic are fused together. I used epoxy to seal the crack. The odor was resolved immediately. It’s been almost a year and I have not had any more problems.

Sadly, when I returned my new $400 pump assembly to the dealership the parts guy told me he sells or ships one of those assemblies out almost daily. How the Hell does something like that not get recalled?

 

You need to file a complaint with NHSTA, and hope (no organize thru the form) others with the same problem file too.

Mark
Retired FF/Eng