I've had this problem for some time. I even installed a second pump because I thought maybe I reached that point with adding more water blocks and two rads that one pump wasn't enough. Now I don't think the first pump was a problem at all. I first went to a dual pump single loop setup, now I"ve gone to a dual loop system. I separated the graphics cards from the CPU /RAM blocks. The graphics loop is still using the original pump I began with over a year ago and wow! That thing runs water through it like a faucet. Now the CPU/Ram loop is the one that shows the trickle in the res. Once I filled the loops it only took about 15 to 20 minutes for the GPU loop to totally clean up the air. It's been hours of running the CPU/Ram loop and the EK memory block still has a bubble in it that doesn't appear to be moving. I guess I know how I'm spending my upcoming weekend. I have to isolate what it is in that loop that is causing the slow flow. Problem is all my plumbing is made up of Bitspower fittings. No tubing. I have some tubing and barbs to do bypassing but it's a lot of work no matter how I look at it unless I find it on the first try. My fear is the rad is a bum component. At $100 a rad this can hurt. If it is the rad that would mean that it would be the 5th item I have bought from Performance PC, almost in a row, that has been defective. I have already terminated my purchases from them because of bad treatment when I mistakenly bought a G-Vans Fan controller, which is defective, and they wouldn't take it back. This rad, which I suspect is bad, is a rad I got as an RMA replacement for the first rad I bought from them that was damaged in shipping. I had a beotch of a time getting them to take that back. Anyway, sorry to rant, but I'm just not happy with my rig right now. It's a lot of money, and I would think that being smart enough to build these things, which I am, the stuff should work.