2001 Toyota Prius bleeding the Inverter cooling system?

I have a 2001 Toyota Prius. The Inverter cooling pump was replaced and now I have problem bleeding the cooling system? The inverter cooling pump is CAVITATING...
I have gone through this process at least 10 times, but still the pump (which I had to replace it) sounds like a water fall with too much air on it.
1)Turning on the car for 5 to 20 sec.
2) Turn it off
3) Loosening both bleeding valves together,
4)Refilling the reservoir tank,
5)Tightening the valves and start from step 1 again and again.
I did this process for more than 10 times, no air is coming out of the system any more, but I still don't see ant turbulence in the reservoir tank.
Should I try bleeding the system just with one valve? (which one) or both together? Or one by one.....