If it's in the upper tank, the worst it can do is clog up a few tubes- - - - -not likely to get debris back into the engine, etc. I'd suggest finding an oldtime radiator shop where somebody still knows how to take a soldered radiator apart, and get them to pull the top tank off and rod it out. The only guy I know in my area who still does that is a second-generation radiator man about my age. When he retires, I have no idea where I'll get the old stuff worked on!
Jerry
