My friend and partner Ray was changing out the engine compartment fuel hoses on a very original 250sl. The new hoses came from Classic-Mercedes Parts in Belgium, an excellent supplier.
We discovered to some dismay that the input fitting on the fuel filter was leaking. The problem was that the swivel nut on the hose fitting was too long and it was tightening against the filter fitting without tightening the nipple. The pictures show the problem, and the fix with a filter fitting that is 2 mm longer on the hose side than the original fitting.
If you are replacing this hose, you may want to watch out for this problem.
One of those "it can go wrong, it will" gotchas.
Cheers,
CT