I have also had this issue as well, but i didnt mind it with mine cause it became UV reactive when it got cloudy so it kinda looked good under a cold cathode UV light.
But i had alottttt of air and bubbles in my loop for a long time, so i put about 1/8 of a cup of tap water in the RES.
After 20 minutes the loop was cleared from any cloudiness (also loosing the UV re-activeness) and after 24 hrs there was no air or bubbles whatsoever. Ive been using the Koolance coolant.
Ive heard that its not recommended to use tap water but hey it was magical in my case. Temps are even better than before by at least 10c
So before you flush, im suggesting to try the tap water, then bleed it.BEFORE: