Radiators with plastic tanks are anathema. Don't waste any time playing with it. They cannot be repaired, they cannot be patched. If the $104 replacement has metal tanks, burn a steak as an offering to the automotive gods. Plastic radiators were not created because they are in any way "better" for you, the owner. They were created because they are (a) lighter in weight, and (b) cheaper to manufacture. In other words, they are "better" for the manufacturer, but any professional mechanic or radiator shop hates them.