Fuel leak in trunk

[Kazoo]

Good morning...
I'n the trunk there are two very small plastic lines that go into the bottom of the fuel expansion tank.  When I smelt fuel in the trunk I found that one of them is cracked and almost broken off - right where it attaches to the bottom of the plastic expansion tank..
Can any one recommend a fix?
The attachment is curious and almost seems plastic welded/melted together??
Also after driving the car, a ton of pressure builds up in the gas tank , it this normal? When I opened the gas cap there is a big pressure release.

[Paul & Dolly]

Hi,
Hav a readof the technical manual, here, under fuel system/tank/venting/ect, and your situation may become clearer there are different systems dependant on which car you have.All parts are available for the earlier system.
Paul.

[mmizesko]

I have same problem.  Fairly common in the 70/71 years.

the plastic nipples crack, and a leak ensues.  we put new clamps and spilced the hoses to grab on tho the stub of a nipple from the expansion tank.  Still have issues.

The best answer is to only fill your tank to 3/4, and you shouldn't have an issue.

Mike Mizesko
Columbus, OH

[Kazoo]

I have a later model 1970...
Even at 1/2 tank, the gas comes out of the plastic tank due to the pressure in the gas tank...
Three questions.... Please
1. Does anyone know if the tank and the little hoses are one pre made assembly, or are there connectors  for the little hoses that could be replaced?
2. Would it be a mistake to just plug the hole and the hose, basically restricting the function?
3. Is it normal to have all that pressure in the gas tank, or should the gas cap be venting?
Thanks all...

[mdsalemi]

Kazoo,

1. The early tanks had brass ferrules, and used fuel line and clamps. Later tanks were one piece, and the plastic lines were molded into/out of the tank.

2. The purpose of the tank is to collect expanded fuel which then will vent off with the FST (funnel shaped thing) that exits at the rear of the car.

3. You really shouldn't have much of a smell in the car's trunk if all the lines have integrity. The tank was available some years ago as a replacement.

[Tyler S]

This thread has a lot of very good info about the venting system and blockages.
http://www.sl113.org/forums/index.php?topic=23943.msg171572#msg171572

[Naj ✝︎]

Your late car will have the bigger vapor tank on the left in the trunk. The vapors vent into the bottom of the engine block.the vent line from the tank runs under the car along with the brake and fuel lines. This line may be blocked or crushed. You can also remove the vapor tank and check for blockage.

Naj

[Mike K]

I had a similar issue on my '71 280SL. There was a blockage on one of the small fuel lines that runs from the filler neck to the venting tank.

I removed the venting tank, cut the lines which are plastic-welded to the venting tank, cleared everything out with an air compressor and spliced in new fuel lines. I also replaced the grommet which is under the car.

Best,
Mike

[rbouch8828]

I just picked up on this thread and saw the overflow tank you have. My 1970 does not have a tank, just two hoses from the fuel tank that end in holes in the trunk floor. Was this ever a correct method?

[Shvegel]

I think what you are seeing is someone who removed the tank and simply ran the lines that come from the top of the tank under the car through the 2 holes in the trunk floor. Not overly safe as fuel will leak out if you fill the tank to the top.  If they plugged the lines you will have pressure vacuum issues on the tank unless the cap gasket is bad or the cap is an aftermarket vented cap.

[rbouch8828]

Thanks. I just ordered the expansion tank from Thomas at Mercedes Classics. Now I'll have to figure out how to install it.