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Hi,
I have a Fluval 405 that is approx 8-10 years old - I've maintained every part of it well - and replaced parts as needed. In 2012 I did replace the impeller and associated parts. It seemed fine.

In the last month or so, I started to notice that I could feel a sort of rumbling in the floor near where the tank is - and it was obviously coming from the canister. I did a media change and cleaned out the impeller (no - I didn't lose the little rubber thingy in the bottom of the impeller well).

The things is still quite rumbly. (probably NOT a word in English . I know I've gotten what is probably beyond the usual lifespan of these units... but I am still unemployed (4+ years now) and it's hard for me to justify buying another filter unless it's pretty certain that it is the Fluval 405's motor that is causing this.

I do have an XP3 in use on my other tank - it's fairly new - it's great. That's a 70 gallon tank with the XP3 and a 10" RES (female).

The smaller tank (55 gallon/8" male RES) has the OLD Fluval 405.

I'd just like to get some feedback on whether people suspect that it's probable or certain that it's time to replace the 405.

I CAN live with the noise - but it sort of permeates the entire dining room - very low frequency and rumbling. I tried putting a towel underneath it which helped a bit - but not enough.

Thank you! (and I tried to 'search' for my question but didn't come up with anything specific - so I apologize if this has been asked before)

It's probably the impeller as that's the only mechanical moving part.

Take a look at the impeller shaft and the hole in the impeller. If it is even he slightest bit oval, it will vibrate when spinning and rumble. Also check for any debris in the motor housing where the impeller magnet goes. Same thing, a grain of sand or something in there will have the same effect.

Make sure all of the parts are assembled correctly (not saying you didn't but somethimes a piece will work it's way loose).

Another issue could be a slightly bent or imperfect impeller shaft. If its not straight, the impeller wobbles and vibrates.

It's very possible you got a defective impeller or impeller shaft.

Also check the little cap in the lid that holds the impeller in place aka the "well cover". If the plastic is worn, it will allow the impeller to wiggle and vibrate.

If the filter is running, its moving water and the rumbly noise is constant, it's something with the impeller or shaft. If the filter is pulsing/surging or short bursts of noise, it could be a problem with the electro magnet (motor).

There aren't any moving parts in the "motor". It's just an electro magnet that alternates current to spin the magnetic impeller shaft. So if you feel a mechanical vibration, it's coming from the only moving part - the impeller.

Your 405 is fixable. The "tune up kit" has all of the pertinent parts.

http://www.fluvalparts.com/servlet/Cate ... -405+Parts

thank you - this is what I figured. I need to check the impeller assembly as a whole and decide if I should just replace the parts - I think I did replace the shaft itself earlier in 2012 as well as the impeller, so it's probably the way I've got it seated. There was a post I came across on a Yahoo search that talks about cavitation - the person seems to know what s/he his talking about as well: http://www.aquaticcommunity.com/aquariu ... 44239.html It is from someone called terrapin24h about half way down the page. I don't even follow the 'physics' really - but I get the point - my impeller assembly might not be properly assembled... and if I play around with it it might just make the noise go away. If not, I'll just buy new impeller parts - which should fix the problem. I have 'some' idea what to look for now that you've mentioned what might be out of shape or normal parameters. I figured it was probably something like this - I don't know what the 'motor' is like - -but it sounds like it doesn't even have moving parts and couldn't be 'responsible' for any rumbling. I gather that it has to be the impeller and associated assembly. Thank you.

Cavitation shouldn't happen on a 405 unless you're introducing air from an airstone right near the intake of the filter.