Aye, the rig was all taken apart with the components lying on a shelf ~15ft away. I'd plugged all the free tubes with cotton since I knew I'd be spitting metal dust everywhere, but it'd seem I wasn't careful enough.

I'm ordering some new tubing this afternoon, I'll be flushing it out and replacing all the tubing when it arrives.  In the meantime, is a little rust going to be a problem for my copper/nickel blocks and rad?

I'm thinking I'll need to take the pump apart and clean it out thoroughly - if it is steel dust it's likely been collecting around the magnetic fields in the motor..