I took quite a few pictures of before and after my repairs.  These are the BEFORE pics.
Forgive the repetition but I'm trying to show details.  The metals used in this expansion tank are the real deal.  No aluminum, plastic or glue here.  They don't make components this good any more.












I keep showing the same crack several times for a better understanding of the migration.  I can see lead in the seam but the crack extends below the seam causing a leak under normal operating pressure and temperature.

This starts the beginning of my repairs...
I drilled holes through the tank in three places.  Then I soldered three silica bronze rods in place with brass washers.  Some ends also have brass nuts.  After doing a few of the threading for the nuts, I realized they really aren't necessary.  The washers are a tight fit on the rods, and they tinned very well.  BTW, this isn't lead.  It's an alloy much stronger than lead.  After soldering, I used a grinder to dress the ends so you can see the different metals used.




I soldered the crack, then I reinforced it with a brass piece.  The solder is sufficient to seal the crack.  The extra piece is formed to the contour of the flange and it will serve to spread any stress around the crack.  Again, this is not lead, but a higher melting temp alloy.






This is the witness mark left by a leak.  I would really like to see the top part assembled but looking at this, it appears the gasket was sealed.  I don't see a trail running down the block and over the water pump flange.  This could have been caused by leaking coolant from the back side of the tank neck OR under the top bolt in front of us.  It's hard to tell from one picture.  I see some corrosion on the bottom washer, so I suspect the split on the top washer is facing towards the heavily rusted area.  Again, hard to tell.

If these flange bolts go into a water jacket, they should have pipe sealer (with teflon) on them.

This is Ford's newer style tank with reinforcement ribs.

Yep, looks like we're running 13-psi or 90-kilopascals.