Can't replace gas cap
 

I have a 99 SL 500 whose gas cap leaks air and causes the check Engine light to go on. I got 2 replacement from MB but they broke and they suggested I use a prior year but it ran into the same problem. The parts Manager believes the current one is worn and that is the only reason it works. It's the original gas cap. Picture of the attached one will show what happens the pieces separate? Has anyone ever had this problem. Am I looking at replacing the gas tank or is the filler tube a separate piece.

Never had this problem, but try swapping the rubber seal from another known good cap and see if that helps. Good luck
dws

I had a bad gasket in the cap of my '98 '500, replaced the gasket with one from AutohausAZ and the problem went away.

Here are is a photo of my cap with the new gasket, and the filler neck.

http://www.paladinmicro.com/SL500/im...FuelCap-01.jpg

http://www.paladinmicro.com/SL500/im...FuelCap-02.jpg

The cap does not have the white plastic collar as does yours--don't know that the earlier one would fit your '99

Got a Blau gas cap and it fits well. Will wait and see if check engine light comes on and if it does will try the gasket.
thanks for help.
Earle

Gas cap
 

So I tried a Blau generic gas cap and turns out it doesn't work either. Was going to try replacing the seal as suggested above. How do you get the seal on and off as MB says is not very bendable and may have to heat (doesn't seem safe!)

On my '98 the seal was quite flexible--no issues just stretching the old one over the locking lugs and installing the new one.

There would be nothing unsafe about heating the cap with a heat gun to remove the seal--assuming it was dry (i.e. not dripping gasoline) and you did it some distance away from the filler tube...