That's the post...
I use that acid too clean rusty parts too, works better then sandblasting, everything comes out nice and grey, but you have to be quick to wash the acid off with soap and plenty of water or else it rusts right away again.
Maybe the crack in the water-pump housing was causing the bearing to be out of alignment with the rest of the pulleys ???
Never heard of such a thing though, but I'm seeing things here on these trucks that I've never seen on any other vehicles before.
Eg... rusty plugs, and not just a little rust, the plugs so rusted that the ceramic insulator blows out of the engine, leaving the rusted steal body in the head.
And cracked heads, usually cast iron is pretty stable and can tolerate some overheating, but apparently not these engines.
After reading about all these problems these trucks have, my British cars don't seem so bad.