I bought this '95 E300 from Dan a couple years ago, and it had a fuel leak
at the fuel filter holder when I picked it up. There are five different
hoses that connect to this assembly, all use o-rings to make the seal, and
one at the top center was leaking. It was a slow leak, Dan thought maybe
the filter holder assembly itself had a defect, so he'd already purchased a
new assembly and it came with the car.
I bought a thicker o-ring, installed that, and it seemed to solve the
problem. Until it didn't. A few weeks ago I noticed the smell of diesel
fuel wafting from under the hood ("Say, is that diesel fuel I smell?" said
somebody's girlfriend on Kaleb's website as she smiles into the camera). A
couple days later it had turned into a gusher, and I had not even been
driving the car. Big pool of diesel under the front bumper.
The leak had returned with a vengeance. Engine running, the middle hose
connection would pulse in and out. OK, time to swap in that new assembly
and some new o-rings, right?
I scrounged around for about 30 minutes until I finally found my stash of
spare o-rings for the OM606 non-turbo fuel system, and then removed all the
fuel lines from the filter holder. Loosened the center bolt / valve
assembly (that holds the big main filter in place) and then removed the
bolts that mount the fuel filter holder in place on the head. Lifted out
the filter and holder, and finished removing the filter on the workbench so
I could hold it upright and not spill anymore fuel. Replaced all the
O-rings, and then got out a new fuel filter and noticed something odd as I
compared it with the old. Old filter, with the MB star mark, has the
center rubber seal just glued to the top of the filter, and it was in two
pieces, floating around the top of the filter and obviously not sealing
anything. New filter (Mahle) has a steel lip folded over the center rubber
seal, keeping it in place.
I suspect that the failure of that center rubber seal meant that the filter
wasn't filtering anything, and so the pressure of the flow from the lift
pump was going directly to the outlet line and that was too much for the
o-ring to seal. I think if I had just replaced the big filter, the leak
would have been solved.
Put it all back together and fired up the engine, leak is gone.
-------------
Max
Charleston SC
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