I just replaced the tube after living with a leak for a few years.
It really wasn't as bad as I thought it would be. Especially, on
a 126 like we have--there's more room to get around in there.
It's been a couple of weeks and the leak has been fixed.

Whatever you do, don't JB weld it. You'll be married to it for life!
No advice on the silicone. The worst part, for me, was getting the
old tube out. I ended up clamping a chain onto the tube with vice grips
and pulling it up and out using leverage.

To insert the new tube I slid the grommet halfway up the tube,
shoved it down into the oil pan seating the grommet and then pulled
the tube up into the newly re-attached upper tube. The grommet will
come out a bit, just used a stick of wood to push down and re-seat the grommet.
Really wasn't too bad of a job.

Jeff

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1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end