Thanks, Mike. That's probably the right track but I have to give credit to the PO. This fellow was open about all the problems with the car and sold it as a non-runner (though I drove it 30 miles home). He did nothing to pretty it up to sell. He just wanted it gone. So maybe it was neglected and at some point then serviced to where the cooling system was cleaned but the impeller didn't recover.

I don't know iron from steel. I know it's ferrous

Sixto
98 E320s sedan and wagon