Hi all, I have a 2011 C300 Sport Automatic rwd. I filled up yesterday on the way home from work and when I went out to the car later I noticed a strong fuel smell but I couldn't pinpoint the location.

This morning I went out to start it and the fuel smell inside and outside the car was strong. When backing out I saw a small puddle that would be located right under the fuel filler door on the back passenger side. I'm assuming this was fuel, given the sircumstances. Fuel smell was strong all the way to work.

Question is, are there any known issues with the C300 fuel tank, filler neck, etc? Does anyone have a place for me to start looking? I searched the issue on the forum but I didn't find anything specific to the C300 W204, just other models that had issues with the seals on the top of the tank. Being that I'm seeing fuel on the ground I doubt that is my issue. Are there any fuel lines in that area that may be damaged that could leak fuel in that specific area?

Any help before I go looking around under the car would be appreciated. Thanks!

 

I found this article while searching Google about a recall of gas tanks by Mercedes. It includes my model and year, wonder if my car is one of the affected.

https://wheels.blogs.nytimes.com/201...for-fuel-leak/

More C300's with similar issue. Does anyone know exactly what the repair entails? Does a while new tank need to be installed?

http://www.carproblemzoo.com/mercedesbenz/c300/other-fuel-system-tank-assembly-problems.php

 

I am guessing that before you filled up the tank there was no smell, correct? And that there was no smell on your ride home as well? If so, it sounds like there could be a hole in the fuel tank or a line got damaged. Did you hear/feel something hit the underside of the car? I would think it there would be a problem with the EVAP system you would have a light on the dash and code would be triggered. And if the leak was there when you filled up chances are you woudl have smelled something right away. It doesn't take very much gas leaking to give you a strong smell. Just a guess.

 

Thanks, correct no fuel smell unless the tank has just been filled. Nothing has hit the underside of the car before I noticed this issue.

I posted two links above that I found online. Appears this may be a common issue with the C300. I'm just hoping I don't have to get a new tank installed.

 

That recall article states that it involved 5,800 cars spread out over a number of different models and that was back in 2012. I would think by now most of those would have been fixed by now and the chances your car could be one of them would be pretty small, but check out the VIN range of the recall. You might get lucky. If your VIN isn't included in that I doubt Mercedes would do anything as it is an 8 year old car.

 

I saw the same and agree. After more research it looks like the "fuel pump closing cover" gets hairline cracks in it and causes the smell/leaking issues. Should be easy enough to replace, just need to find the part number for it and the gasket.

 

Good luck! Hope it is relatively easy to fix and not too costly.

 

Thanks! Looks like it's an easy job and the part is about $50. Hopefully that is the issue.

 

Just want to close this thread out with the fix to the issue. Turned out that the Fuel Pump Closing Cover has a flaw where it develops hairline cracks in it, thus letting a bit of fuel and vapors out when the tank is full.

I bought a new cover and gasket from the dealer ($70 for both) and changed them in about 20-30 minutes.

Here are the part numbers in case anyone comes across this later. For a 2011 C300 Sport 7 speed auto.
211-471-01-79-64 SEAL RING
204-470-04-38 CLOSING COVER

 

I had the metal seal ring rusted and broke resulting in fuel coming out when the tank is filled.
What tool did you use to tighten that seal ring? It's pretty tight space there.

 

Mine was different for whatever reason. I had 6 8mm bolts holding mine down instead of the one the rotates to tighten.

From what I've seen online, and what I've done in the past you can take a flat head screwdriver and mallet and tap on the ears of the ring.

 

I fixed it.

 

I also had the same issue. Easily replaced it.

 

The seal ring show incompatible with my 2010 C300 when I try to buy it through Mercedes or Amazon but I bought it anyway. Is this the right part?

 

Aznmode- That is not what the seal on mine looked like. My car is equipped with Code 917- PZEV, and the fuel filter on the left side and the fuel pump closing cover on the right side both seal with:
2114710179
Fuel Filter Seal

It's a really thin bright minty green seal.

 

So I've replaced the right side cover and gasket but error code P0456 still pops up. I decide to check the driver side. No puddle but the the longer connector has these 3 rubber plugs that had some fuel moisture. 2 of them were off for some reason but put them back on. I think this is where the leak is coming from? It wasn't a lot of fuel so maybe not. When I had leak there was a puddle in the driveway on a full tank. The other connector had some oily gunk on it but didn't smell like fuel. It wont be safe but I think I need to fill up again just so I can see or trace the leak better.

 

Looks like this is where my leak is. Finally filled the tank and there was gasoline here. Anyone, know the part number by chance? TIA

 

Replace that plastic closing cover, part # is from OP’s post #9. Look closely, you’ll see a hairline crack which is enough for gasoline to come out.

 

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I already ordered 204-470-04-38 that OP recommended and replaced the passenger side but unfortunately the side that is actually leaking on mine is on the driver side. I should've filled up the tank to test instead if assuming I had the same side leak as everyone else here. But I was too worried of gas leaking out the car. But anyways the driver side cover looks very similar to the passenger one but this one has a center hole {see image). That image is of an afterarket but cost way more than an aftermarket fuel pump assembly on ebay which includes this cover. There are other used oem covers but I worry about those so I'll just buy the aftermarket fuel pump assembly instead and just grab the cover.

 

So I have the same problem that you did on the drivers side. I ordered a replacement fuel pump expecting to use the cover as you suggested but the unit is all one piece. Did you have to replace the entire unit as well?

 

Ya mine came in 1 piece also so I need to replace the whole thing. Just haven't gotten a chance to yet. I saw a YouTube video on it, looks pretty straight forward. Did you also buy the 0 ring green gasket? Might be a good idea to replace that also.

 

On my car, which is equipped with Code 917 PZEV (the components are different if you have a PZEV vehicle or not), the fuel filter is what closes the drivers/left side. The top of it looks just like the fuel pump closing cover (except also has a center hole) from the passenger/right side, but underneath is the whole fuel filter unit where I recall 3 hoses connect to it.

So, in my case, when my left side cover was leaking, I needed a new fuel filter (which I ended up struggling to connect, as described in https://mbworld.org/forums/c-class-w...ml#post8535520)

 

Yes, I got the O ring as well and I see some of the videos. Will give it a go this weekend.
Thanks for the help!

 

This is the old unit located under the back seat on the driver's side.
Gas filled up in the bottom of this picture (rear of car) then overflowed and dripped out the bottom of the car.

I disconnected the wiring plug and the top hose connection on the right hand side of the photo (rear of car).

Then I could get to the hose connection on the left hand side (front of car).
Gas squirted out of the hose when disconnected. Remember it is full of gas!

Here are the three hose connectors and wiring connector.
I replaced the green O ring shown in the photo.

I put the new one in in reverse order. Left (front) connection first and then the two right (rear) hose connections.
There was enough hose to have the unit above the hole to get the connectors on and clips pulled outwards (to lock).
I had to fish the wiring plug out of the tank for the last connection.

New unit installed.

Suggestions:
Have as little gas in the car as possible and at least less than a quarter tank. It will be easier to fish the hoses out and clean out any debris that falls in.
Two of the hose connections are tight. Take your time and work the u-clips inward to pull them off.
Check the small wire attachments on the fuel filter as these get bent when installing the unit. I pinched them tighter before and after.
I got the fuel filter and green O ring off of Amazon and they fit fine.

Good luck!

 

Nice DIY!