I'm pretty sure IanY means two things:

1. Use tap pressure to flush your rad (tap pressure is more than a D5 I'd think) or you could...
2. Use a pressure washer etc (if available but not recommended).

twwen2 I'm confused is the loop you setup what you had been running for a while or was that new liquid mix?

Only reason I ask is i have had distilled and Fesser Clear/UV in my loop for a couple of months and found no gunk in my blocks this weekend when I took it apart. Is it possible that this was just stuff from your rad?

Just wondering thats all.

Sweet looking build and photos.