[Laura G]

I have a '73 Ford E100 van. I tried to repair a small leak with stop leak, but after two minutes, I had to turn off the engine because of a larger hole that opened up. I flushed the system with water and replaced the radiator. I found a metal like substance in the thermostat housing that wouldn't come out, even when pounding on it, which I think may be the stop leak since I didn't run the engine for 1/2 hour as directed. One parts store told me to spray a solvent (engine degreaser) directly on it and flush it with water before flushing the entire system with radiator flush. Another parts store told me not to use engine degreaser, and that I should try filing it down since it may be metal flash castings. How should I get this stuff out of the housing and what should I do to make sure the stop leak is out of the whole system?
Thanks for any advice you can give...