Inside Smells like gasoline Only when speed 65+mph and no AC
 

Need Help! My 2006 CLK500 had a problem.
When driving on Freeway, 65mph+, if I don't turn on the AC, inside of the car will smell like gasoline. I need to open the window to not die inside the car lol.
Doesn't happen if go under Freeway miles, turning on AC will reduce the smell.
Not much Mechanics fix MB around me, don't want to go to the dealers.
Changed glove box air filter, don't see gasoline leaks from just looking under the hood, maybe deep down, idk.
Also, should I replace the valve cover if never been replaced? Reasons?
The car had codes saying: Right Substitute Light On and Right Lamp and Left Fog lamp something, but when I look out, nothing was wrong.
WHAT DO I DO?!
Guys plz help me out, just got this car half year ago, new to this community.

there is a common problem with the fuel pump seal on the gas tank. try lifting the rear seats... there is a latch there on the window side of each cushion. even on hard tops. you may be able to smell is there if the leak is fresh. but i think this type of leak is more common with full tanks of gas?

but yea, fyi, there is an updated gasket. look thicker. but yea, easy to lift the rear seat and smell around. i was able to smell it on my car when i bought it.

i never tried it... but i think the carpet that covers the fuel area actually starts in the trunk too... so you might be able to smell it there also? like... check if you smell it inside the car, do you smell it in the trunk?

In addition to the seals on the fuel pump and sender units, the sender unit can develop a leak where the pressure sensor is attached. If you look at the top of the sender and see that it is discolored, and dirty, then it has been leaking there. Officially, you'd need to replace the sender unit (which often mean replacing the pump, too, because its plastic connections may be brittle and break when disconnecting the hoses). Some people have had luck cleaning the sender and then coating it with epoxy all around the pressure sensor.

Sorry for the late reply, anyway,
When I bought this car, the guy before me had just changed both the fuel pump, he hasn't got the rear seat screws back yet...
And there was no smell when you rip the rear seats off. No smell from Trunk.
No leaks from Valve Cover.
The smell seems coming from under the car, is there some other things I should check?
Also, the car needs 1-quart engine oil every 2 or 3 weeks now. Maybe the PCV? Where is that even located on this car?

You should check with Rodney, but I think there may a pressure relief in the neck between the tank and the gas fill opening.

There is no PCV valve. Instead, there are "breathers" on the valve covers. Given the oil usage, I am wondering if the smell is burning oil and not gasoline. You say there are no leaks on the valve covers, but that's the first place I'd look. Often, it's the right (passenger) side that leaks oil onto the exhaust manifold. Check for discoloring on the manifold.

There is a complex system for recovering fumes from the fuel tank, and it's monitored by the ECU. If it were leaking, you'd most likely have an MIL (check engine light) with a code indicating a leak.

Thank you for your reply!
Actually, the only messages I have on the dash are Left Foglamp. Tail lamp, right. And Tail lamp right substitute bulb on.
There was no check engine light on, and I don't think those messages above may relate to the actual problems.
Anyway, the breathers that you were talking about, I'm not sure but Mercedes, but should I replace those as one of the problems causing the smell?
I am pretty sure the engine is burning engine oil because now I need to add a quart oil every 2 to 3 weeks now, but for the smell, I think its burning gasoline.
There is dust in the passenger air intake hoses, not sure if that affects the smell, other than that, there are no leaks on the manifold except some dust laying.

Did you ever look under the rear seat. Takes 10 min and it's free.

hi there
this is my first post here so forgive me if I'm in the wrong place . I too have a fuel smell /leak It originates at the drivers side rear wheel now with a flashlight I can see fuel has been leaking up in that area . it's is CLK500 2006 67 K MILES now I'm not a bad weekend garage mechanic what could be the issue and what parts would i need to buy in advance , seems there might have been a recall on these cars from some posts I've seen already . ANY info is truly appreciated and any specialty tools to pull out the tank and replace seals & hoses , Thank you in advance.

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This is common. The connection on the fuel sender (the unit on top of the gas tank on the left side, under the rear seat cushion) has a port where the pressure sensor is connected, and it leaks. The official repair is to replace the sender, which often also mean replacing the pump (on the right side of the tank) as the hose connections on it are brittle and break. You should also replace the seals as they were revised to be thicker. Now, an unofficial repair that some have had success with is to thoroughly clean the top of the sender then coat it with epoxy.

I had this. I had a small fuel leak from one of the small sensors on the fuel rail. How the car didn't go up in smoke
is beyond me. A small mastic repair sorted it.