Just a thought. But since this same thing happened to me a very long time ago. Pull the fan belt off. Turn the fan by hand. Sticky? Rough? Or just stuck? No leaking no noise, and bang. The water pump into the radiator. Different motor, and different car, but the things it was doing are the same, limited RPM, Lowered oil pressure(I think the drag on the engine caused that) and last, but not least..a short squeal. The noise was a combination of bearing death, and major belt slip. If I had stopped then. I might have saved the radiator, fan, pulley as well as the front half of the water pump(Buick V6 in my old Jeepster). Fastest radiator drain I ever saw. It even impressed the Highway Patrol car behind me. No issues with the law. And he had a tow for me before I rolled to a stop(nice guy). Jeep Radiators are about as hard to find as our truck radiators are(spendy too). Any way, If the oil is clean, and the filter is clean, I would for certain check the water pump. Last year we put a 235 into a 48 Chevy sedan. Went the shortened pump shaft and...then lost the press fit for the fan support. That cost a fan, and radiator as well. Why the machine shop never said any thing about the easy press I don't know(I don't take parts to them any more) Would have been nice to know. Long story I know, but check that water pump, please?
