Originally Posted by Awaz
Unfortunately, the pump either works as expected or is very noisy. I had a noisy one - dish soap did not help either. I finally had to get it replaced. I would try the dish soap method though. Take it out - pour a few drops through the pump outlet. Let it sit on the side for a few min, turn it the other side and let it sit. Then try it out. Your water will get all foamy, but just leave the res cap opened. All you should hear is the water whoosing due to bubbles.
EDIT: Also make sure it is mounted properly. After I got my second pump, I occasionally can hear the pump. Goes away once I move the case a bit. I finally had to jam some foam on the sides, top and bottom to isolate it from the case more. All I can hear is a slight hum just like I would expect from a pump - and that only if I get real close to it. The first pump I had, I can hear it from outside the door of my room - about 10ft away.
Hmmm, I have a really noisy pump (not from a rasa kit, but it's the same pump), I had assumed it was just the mounting since it wedged into a little server case. I might review that.