OCModShop has posted a cleaning copper waterblocks guide
Here you can see some of the residues left on the acrylic tops from such a long period of use. Most likely under closer inspection, you could find a similar residue over the surface of the interior of your copper blocks. Just as dust hinders the performance of air cooled heatsinks, these residues or corrosion can hinder the performance of you blocks by adding another thermal interface material between the coolant and the surface of the copper...Read more
