Noisy Canister Filter. Please Help It Driving Me Mad Lol

[NatashaWoo]

Go i have a superfish aqua pro 400 canister filter. It's been running for 4 months absolutely silent. 2 days ago it started making an annoying humming noise. I Unplugged it cleaned filters, impeller and housing for impeller. Tightened up pipe fasteners and noise stopped. Came home from work today and it's making noise again. When i had my old filter it made this sound when there was air trapped, but i can't figure this out

 

[Ch4rlie]

Air being trapped was my first instinct as well to be honest. Any trapped air in the hoses / pipes?
 
Sometimes with cannister filters, the air trapped is inside the head part of the filter, try tipping the cannister to try and dislodge the trapped air.
 
Is there anything at all in the intake pipe, or even in the intake hose at all, don't imagine tehre would be anything, worth checking anyway.
 
is the impeller true, meaning straight as a die?
Spin it in between fingers quickly, if it wobbles or not quite stright, that may account for a quiet humming noise perhaps.
 
Basically its a process of elimination to try and find the culprit of this noise, then next time it happens, you'll have an idea of what to do.
New filters can be tricky to figure out whats the issue is. Trial and error.

 

[NatashaWoo]

I haven't a clue. I'm pretty sure its air but don't know how to get rid. I've tried shaking box slightly side to side to dislodge bit nothing works

 

[nic1]

Normally when my filter makes a noise I give it a bit of a shake while its off, and then another good wobble/shake when its on for about a minute. its usually air for me.

 

[Lunar Jetman]

You could try tilting it for 45-90 degrees. That usually helps clear mine.