Liquid cooling problems

Lately my liquid cooling system has been very noisy, I can hear it pumping the coolant, it gets louder and then quieter. Looking at it though I can see air bubbles in the coolant lines and I notice that instead of coolant moving in one direction(in one tube back out thru another) it's going back and forth in tubes - is this how its supposed to move? And the noise corresponds with the coolant flow - any ideas?? The CPu is not overheating the temp gauges are reading normal. I worry about the air bubbles - if air can get in can coolant get out????

Any advice on which one to get, or what I should look for in one.

Here are some flow meter's you can look at but I would stay away from the swivel nozzles, very awkward. The swivel nozzles are cool for stationary part only in my opinion.

http://www.koolance.com/water-cool [...] p?cPath=70