[Scrapper]

i gree with dad it will cause a sludge now you have that in heater core probably you can buy a flush kit for that and if it don't get sludge all out you'll have to pull rad have it cleaned or boild out. to your rad plug i'd spray some pb blaster to spray on rad plug and try to keep moving back and forth see if will relase it if you still can get ahold of the plug now?

good luck..........