95 E300 mystery fuel tank leak

[clickclak]

After getting the tank almost empty, I removed my fuel tank screen filter the other day to clean it and replaced the gasket with a new one. Before starting, I jacked the passenger side rear up so that the car was leaning on its driver side, to make it easier to access the tank screen. After getting everything loose and replaced, and covered with diesel fuel in the process, I tightened everything and cleaned up. I opened the trunk and smelled diesel, removed the false wall separating the tank from the trunk and saw diesel fuel accumulating under the tank; it was also leaking from a pinhole in the car body under the car, just forward of the spare tire well; also, fuel is leaking from the driver side front and rear water downspouts. I cleaned up and drove to get some more fuel in a spare container. After opening the trunk again due to smelling diesel, I discovered more fuel had leaked in to the same area as before.

I then went back home, removed the fuel screen again to check the gasket, then resealed everything. Fuel again leaked from the driver side front and rear water downspouts located next to the jack mount points. I parked the car overnight, thinking that some fuel which had leaked between the hole for the tank screen and the body during the removal process may still be trapped and need to drain overnight.

This AM, I discovered more fuel had leaked form the pinhole under the car and the driver side rear downspout; a little was left in the trunk. I cleaned it up and drove to a store, where again I checked the trunk only to discover more diesel fuel leakage; I went to local MB dealership and got a new gasket, came home and changed it out again. Fuel is still leaking into the trunk and out the downspouts, the tank is on empty according to the gauge

Is it possible I jarred a line or connection loose during this process that is hidden on the other side of steel fuel tank facing the rear seat bulkhead, thus causing a leak? Is there an air vent or overflow vent tied into this that could be causing the problem?

[Diesel911]

It is hard to say without actually being there. However, you are dealing with 20 year old rubber Hoses and seals.

Another problem for me is I don't own the Vehicle you have and have not seen any pictures or parts diagrams and have no idea what your Fuel Tank and hose setup looks like.

On my own year and Model I found that rust had buit up under the Rubber shield on the one of the Clamps that kept the Steel Fuel Tubing in places. It was not dripping but you could see the area around it where the Fuel Leaked.

Of coures when I removed the Clamp the rusted gunk that was partially sealing it off cam out and I had a really good leak.


At the bottom of the Fuel Tank if there is any sort of brazed or welded on tubing/goose neck that a Hose slides over I would check that closely. Vibration can cause brazed and welded joints to crack and if during the process of wrenching you bumped into a goose neck that will sometimes crack them; usually where they are attacted at the Fuel Tank.