One last thought... This tank is the normal type, wood gets the water hot
and a pump circulates the water. Not a boiler where you use steam...
If it's the normal type there should be a vent, if the vent 'was' plugged
it MIGHT have increased the psi enough to do that (weak spot) and now that
the vent is clear it doesn't get enough psi to force the water out.
<Shrug>, just a guess.