Chazz - Yep,
http://www.procooling.com/articles/h....shtml#H2OCool (A must read in my opinion)
Nice diagram
The ideal set-up would be an inline air-trap similar to this -
This is intended to be the highest point in your system - good example
Notice how the inlet is under the water level (bubbles rise) water free of bubbbles goes outa the bottom outlet. continuously actively purging the entire system. Looks Kool too
U could easily mod a res/pump to get the same effect, or even fix a partition into the side of the vessal to prevent bubbles gettin sucked down back into the loop.
Viper what are you makin the res out of?
Mat