there is alum "solder" out there, dunno brand names, have never used it, melts bout 700 f, and uses flux
acetone and hp air should clean crack, some heat to sweat it might help too

dont see silver solder workin on alum

 

This one maybe?
Bernzomatic AL3 Aluminum Brazing/Welding Rods with 12-Inch Rods of Working Temperature 720-750 Degrees, 2-Piece https://a.co/d/55QlLRN

 

The NPT thread ( taper ) is the problem ... Jackie's idea is worth a try ... Forget the silicone suggestions ... Is there another location to get an oil pressure reading and totally plug the existing location ?? ?

 

2008 manual torque 50 in-lbs. No torque wrench, no feel for what snug means, result as seen.
2017 manual torque 60 to 90 in-lbs. For existing switch apply Loctite 565.

 

Jackie's suggestion does involve silicone eg permatex.

I'll see about other possible locations. But even without the oil switch, I'm OK with.

 

Post 18. Reference Permatex #1. That is a quick setting harding for permeant fitting that are not intended as a maintenance or service.


That's​​​​​ for sealing the existing cracked holes using gaskets. No gasket material left exposed on the inside.

Endless detail and come backs assure me you should not try what I have suggested. .

Don't disable the oil pressure light.

 

yep, should be a powder flux, too
look on yt - alum brazing or solder

links dont wanna c&p here
was one w/flux coated rod

 

3 threads, hand tight is a good npt test fit
tape or loctite 545 does same job
only need couple wraps w/tape on small fittings

 

I was going to add that at just over 4 ft-lbs of torque hand tight might be good enough.

 

I'd have someone very familiar with tig welding aluminum and engine case repairs see if they were confident it could be welded. But I would not use any silicone type sealer inside the engine as it would come lose and cause lots of other problems you don't want.

If any sealer were used, I'd clean the area multiple times with brake cleaner to remove as much oil as possible. Then use glyptal to seal the area inside and out, even if a competent welder could make the repairs. Glyptal was used to coat the inside of older Harley and Indian engines because the early castings were prone to porosity and would seap and leak. And used frequently with electrical motors. It's also used on high performance engines to help oil return (smoother surface) to the scavenger and oil pump return to the tank.

Paul