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Growling sound from my Rio 400 pump ????

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Mar 28, 2001
I just hooked up my new water cooling system. Im using two radiators, so I bought a slightly larger pump....the Rio 400. Its just a little bigger in GPH than the standard Rio 180.....I know it sounds like its alot bigger, but it only puts out an extra 40 GPH....compared to the Rio 180.

The problem is, when I attach the output fitting and hose to the top of the pump, the pump growls, which is louder than any case fan I have !!! BUT, when I disconnect the ouput fitting and hose from the top of the pump and just let the water spill out into the resevoir, the growling sound goes away !!!!

So, could it be that there is too much 'back pressure' on the internals of this pump ??? causing it to growl.....So maybe I should get an even larger pump ???

Please help, this growling really sucks !!!!!!
You might actually have to suck start the pump with the attachment on it, cause I know my pump did that until it was actually pumping water through it. Granted, I don't have a RIO, but they're probably all pretty much the same mechanics.
Actually, the system was already primed. No air was in the tubing, waterblock, radiators or anything else.

It still growled, no matter what.......until I disconnected the top ouput fitting and hose. Then the noise went away. It seems like I said, too much 'back pressure' on the little magnetic impellor.....which is causing it to growl inside of the pump housing.
I had the same thing with my magdrive pump. It was coused by too much back pressure indeed. The radiator I picked up at an autocemetary, seemed to be stuffed up with brown drab. Had to flush it a couple of times (both directions!). No my setup runs flawlessly, no more rattling, only when I bend tubes to much.
Mr. Murphy (Apr 23, 2001 02:22 a.m.):
Now my setup runs flawlessly, no more rattling, only when I bend tubes to much.

Ok....but would have getting a larger pump corrected the problem for you ? Cause with the design of my system, I have to have a number of bends.