[Walt Fricke]

I'd measure this again. 1.75 is normal, so fine usually is 1.5, maybe 1.25 at the smallest. Not 1.0. Maryland Metric's catalog lists a 1.0 for M12 bolts (and for M18), but I don't think that is anything Porsche used.

I also question 12mm. The sender is 10mm, so there would only be 1mm wall thickness. The crush washer in the parts catalog is 18mm, not 12mm.

What I'd do is check the plug on the other end of this hole - the one which holds the pressure setting spring and piston in place. That is an M18/1.5 bolt.I think this has the same thread. You could check that against the steel insert you removed.

If the bad threads are in the aluminum case (and that's what you have said), then an adapter would have to be made from an M14 bolt of appropriate pitch. You want a bolt because you have to screw this thing in (maybe that is what you mean by screw).

But maybe we are talking about the wrong hole in the case? I'm assuming it is on top of the right case half, to the flywheel end of things, and close to the oil temperature thermostat.