I've got a few ML's in the shop now, so I took a look underneath and here's what I found. The steel lines coming out of the hydraulic (located beneath the washer bottle) unit are routed down to the left side frame rail. They are quite close (approx.10mm) to the P/S hoses but if everything is installed correctly nothing rubs. If the line in question is for one of the rear wheel brakes, they run along the frame rail between the body mounts and body shell. In this area they're quite well protected. The line for the L/R simply connects to the rubber hose, while the line for the R/R connects to a union fitting located at the frame rail in the L/R wheel well. From the union fitting it simply crosses over to the R/R. Since the line is pre-formed it could be quite a job to replace. Several hours at a minimum. It would be a difficult driveway job even for the most determined DIYer. The big question as far as I'm concerned is how did the line come in contact with anything? Believe me, they don't just pop out of their brackets. I'm only guesing, but someone must have inadvertantly knocked it loose during a previous repair job. This may have taken place some time ago though. I'm sure it would take a while to rub through. It might be worthwhile to study the service history thoroughly. Try to find out if any previous work was done in that area.