D2 main fuel tank breather detail - need help please!

Sounds like a pretty standard use of a slip fit ferrule and compression coupling. I really don't know anything about what sort of fitting is there through the bottom of the tank, but surely you can find a piece of copper or steel tube with the correct OD and a nut and ferrule to thread into the fitting from the bottom. I suppose you could use a packing instead of a compression ferrule and it might help to prevent cracking. Something like faucet stem seal graphited string?

If I'm understanding you, the main fitting would internally take a compression fitting that the inner tube would pass through, and that's what would prevent diesel leaking out around the tube. That makes sense. Would hard copper be ok? It current has 1/4 steel but it's now too short so I have to replace it anyway.

Hi Team,
from memory, the seat tank breather is built into the tank cap and is held together with a central drilled bolt that holds a plate in-situ, the plate in turn holds a metal gauze type filter medium in a spiral groove cast into the cap.
Only tube I recall in the filler and screen area is a short guide tube for the dipstick/plunger--I stand to be corrected.
Cheers,
Eddie B.

I know what your referring to but I'm not that familiar. The parts book calls out a fitting that the vent screen screws in under the tank. That might be a compression type fitting for the tube and threaded for the vent screen.

Neil, I sent you a pm.

All, here's the arrangement:

[attachment=49688]IMG_5719.jpg[/attachment]

Tube runs from under the main cap down to outlet in bottom of tank:

[attachment=49686]IMG_5722.jpg[/attachment]

[attachment=49687]IMG_5720.jpg[/attachment]

Original main fitting that the tube passed through / into. Almost looks like it was soldered in place. Took a bit of heat and effort to get it out and that "stuff" looks suspiciously like lead / solder:

[attachment=49685]IMG_5723.jpg[/attachment]

Inside of fitting with some type of flare arrangement:

[attachment=49684]IMG_5724.jpg[/attachment]

What I want to replace it with. The large brass fitting would replicate the original with a compression fitting type of face internally, with a hole large enough for the 1/4 tube to pass through. The small brass fitting would be the other side of the compression fitting - the olive would fit in the middle. The small brass fitting would also have a 1/8 NPT so the breather could be screwed into it (breather is top right of photo)

[attachment=49689]IMG_5725.jpg[/attachment]

Hi Neil,
thanks for the great pix of said breather arrangement, do not recall seeing one but, there it is, and not shown in my Parts Books.
Good to know that I have not wasted today and learned something new on these often surprising old Cats.
Best Regards,
Eddie B.

I wonder what the point is of such a complicated breather arrangement when the cap as explained by edb works perfectly well.

I would guess that they thought that it would avoid any diesel spillage out the top of the cap and down the operator's back. But maybe, like the oil cooler, they decided later that it really wasn't necessary. This unit is 5U13753 so middle of the range I guess.