Waaay back when (probably 1980) I had a 1974 Datsun B210 that had weak antifreeze in it and overnight on a frigid night, the coolant froze.
When I started it in the morning, the belts were squealing like mad because the water pump was frozen and wouldn’t rotate. I pulled the belts and ran the engine for about 10 mins at a time for a few cycles to heat everything up until the pump melted enough to rotate. Then I put the belts back on and repeated about 5 more times until I got everything warmed up enough to melt all the coolant.
I missed school that day, but at least I got it functional enough to be able to go get fresh antifreeze and replace what was in the system to give proper freeze protection.
Ever since then, I am hyper aware of the coolant condition in all my vehicles.