I took off my radiator cap the other day to test the coolant in my 94 accord and there was very small dust size pieces of rubber stuck all to the caps rubber seal. Looking down into the radiator I can see the same size pieces floating in the radiator. Only thing I can think of is that these pieces came from a hose.

 

do a cooling system flush and new hoses. the upper radiator hose is notorious for swelling and other issues. make sure u drain the block not just the radiator and pray your water pump isnt compromised