Odd "squirting" sound from water pump

[bitteractr]

Hey all.
So I'm starting a new 55 gallon saltwater tank and have a Mag-Drive 9.5 pump set up in my sump. Pump is working great but it randomly makes a "squirting" or "bubble" noise. I can see NO bubbles making it through the bubble trap because the water level is higher than the ledge (no waterfall effect). It is also NOT the pump rattling against the walls and bottom of the tank (silicone mat solved that).

So what could this be? If it were constant, I would suspect a trapped air bubble inside the pump but it's infuriatingly random but frequent enough to keep me awake. There is NOTHING else in the tank but saltwater.
Any help would be appreciated! Thanks!

 

[ezy33]

Watch to see if the in take is forming a funnel and sucking in air. The air could break the funnel until it forms again. To stop this turn the intake down and/ or raise the water level on the sump. Another cause could be a failing impeller or housing I would clean and inspect your pump. Good luck.

 

[bitteractr]

No funnels up top or down below. Both the sump pump and the aquarium drain are completely submerged.
Took the pump apart and nothing at all inside. Clean as a whistle, except for a few stray cat hairs (again, the tank is literally a giant box of saltwater at the moment).

 

[ezy33]

You could try putting something on the intake if there's nothing there now. Also try turning the pump on its side. What feeds your sump. Could it be the overflow? Most overflows make some noise.

 

[bitteractr]

The overflow is submerged and is a full siphon so that wasn't it. I ended up throttling down the sump pump till it made no noise and then calibrated the overflow accordingly. No noise! But still, what the heck? Why would the pump be making noise if I'm running it flat out? If you have any ideas, I'd love to hear them but I think the problem is solved. I don't need THAT much flow in my 55 gallon anyway. Thanks!

 

[ezy33]

Maybe some photos would help. I've had a similar problem where the overflow would get behind the flow causing it to suck in some air for a moment. Then it would run properly for several minutes and do it again.