correct me if i'm wrong... but as to the original question... can pump PULL from CPU... well iirc, the pump needs a steady supply of water but it really does not have any "pulling" power... hence res is always before the pump and providing constant supply of coolant to it.

it seems that it works best if pump was located to push water through the loop and dump at a reservoir...

just some naive observation...

OP, as for foam, did you clean out the radiator?
i noticed some foaming when i used some coolants such as the swiftech and primochills... but in distilled, no fizz... no foam...

let it run a while and see if it clears.
i too have read somewhere that the temp in a loop pretty much normalizes...