Water pump shaft clearance?

[VicParticipant @vic]

I bought an Aquarium filter a while back and I had to send the head back because it was very noisy. It was returned with a new impeller but it’s still noisy so I’m now in contact with the importer. There is only one moving part on these pumps, it’s an impeller with a tubular magnet with plastic vanes. This rotates on a ceramic shaft. In operation there is a humming noise and vibration coming from the head. I have a similar unit from another vendor and it’s virtually silent. I’ve measured the ceramic shaft with a mic and it’s 2.48mm. Sorting through my drill bits I found the end of a 2.56mm bit just fits in the impeller opening. It doesn’t sound much but the gap between the impeller and shaft is quite noticeable in the hand. What would you expect a reasonable clearance to be for something like this. Anyone have any ideas? It may be that something else is causing the noise but I can’t think what that may be.

I’m not prepared to do it at the moment but next time I clean my other filter I will check the clearance on that just out of curiosity.

[VicParticipant @vic]

[Grizzly bearParticipant @grizzlybear]

Hi Vic,

Picture or link please.

Bear..

[VicParticipant @vic]

Its part number 7632600

https://www.eheim.com/resources/product//219/downloads/10/EHEIM_classic_250_Ersatzteilliste.pdf

 

Edited By Vic on 14/08/2019 19:18:31

[Brian Sweeting 2Participant @briansweeting2]

Might be a silly question but is the pump motor section full of water otherwise a dry running pump will be noisy.

[Neil WyattModerator @neilwyatt]

In my experience these are usually a pretty free fit, although I have never measured one.

They usually hum if jammed or airlocked.

Neil

[Neil WyattModerator @neilwyatt]

In my experience these are usually a pretty free fit, although I have never measured one.

They usually hum if jammed or airlocked.

Neil

[VicParticipant @vic]

Posted by Brian Sweeting on 14/08/2019 23:52:26:

Might be a silly question but is the pump motor section full of water otherwise a dry running pump will be noisy.

Yes it’s full of water. Excess noise is often blamed on trapped air but there’s a distinct difference from the noise trapped air makes and this humming/buzzing noise. You can also feel the vibration through the housing.

The frustrating thing is that these pumps used to be virtually silent in operation when they were made in Germany. Not sure where they’re made now but they no longer have “Made in Germany” on them any longer.

looking on the net I’m not the only one to have this problem, lots of others have suffered it with this particular model and others in the series.

[JasonBModerator @jasonb]

I ran a couple of those filters for years and always quiet, airpump probbaly drowne dit out but expect they were the older ones.

As Neil says they are quite slack, I have another larger pump where the impeller is held in rubber "bearings" and my Messener Koi pond pumps have plenty of freeplay

[VicParticipant @vic]

The impeller is made of some kind of magnetic material. I’m wondering if I can mount it in a collet and drill and sleeve it to get a better fit?

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