Radiator rattle

I just received a MCR-220 radiator from Petra's. Upon unpacking I noticed a rattling sound coming from near the bottom.
It sounds like a piece of metal.
Tried to rinse/push water through unit to get it out but it just stays in the same place. I think it may be a soldier ball.

Do you guys think its safe to use or should I send it back?

You might try soaking the insides with a hot water/vinegar solution for around 15 minutes then trying to fulsh it out and see if that helps. If the rattle is still there after trying that I would just get in touch with the store that you bought it from or with Swiftech and see about a replacment. I would hate to see a solder ball get sucked through your waterpump and ruin it or get stuck in a block.

There definitely shouldn't be a rattle. If you are unable to get rid of it, definitely have it replaced. muddocktor is right; don't take the chance on ruining your pump.

Sending back to Petra's.