A Northstar tried to die, so I had to intervene

2000 Eldorado ETC
It's owner couldn't see the trouble, and he was stuck on a bridge, so he poured enough coolant/water in it to limp it back home, stopping periodically to let it cool
Are the head gaskets done, only time will tell

It had a P1258 (Engine Overtemp code) which means it hit 270°F for 10 seconds or more

That means it inhibited the A/C, forced the fans to high speed, and went Camel mode alternating cylinders to air cool itself

The failure was the radiator drain plug disintegrating
How that happened I have no idea, I found the other half laying on the ABS pump
Did I mention this cars hard to work on?
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First attempt, I tried a Dorman drain plug
The old wallet with wings burned me yet again, it wouldn't tighten down no matter what I did
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I removed the remnant of the old plug, but no matter what I did, it wouldn't click on and tighten down
Must be half a mm different, luckily the part is discontinued from GM
I found a NOS OEM part on eBay
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Finally got it tightened down, all back together
Topped off the coolant, let it purge to the best of my ability
It doesn't blow any smoke, and it doesn't sound any different, seems to hold its coolant

After a major overheating event, it needs an oil change
I drove it for an hour or so last night, to see if it held pressure
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It lives to die another day

I'm gonna berate it's owner that more preventative cooling system maintenance is required
My final words to the Northstar
Maybe for the owner too