HOLY CRAP THAT SUX!! It's really tough trying to seal cracks near threads.
If the crack is along the machined flanged surface (of the hole face of the hole), then you could try adding a gasket washer to seal the leak from around it, but that will be tricky with the sending unit's NPT type fitting...
I've seen ppl try JB Weld but it always leaks again eventually.
Best of luck for ya bud!
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