9410 DC pump making mechanical noises

[B-SMOOTH]

Hello,

@rvitko

I just received this skimmer last week(Friday) from Saltwateraquarium.com and hoping you can help me to diagnose what is happening with what I think is the pump. It was sold as used/refurb, but was probably an openbox item as it looks to be brand new.

I assembled and started the skimmer that day, and it immediately started skimming(and continues to skim wonderfully and without issue), but there is a constant mechanical turbulent sound that's emanating from the pump. Almost like tiny stones being intermittently tumbled. It's hard to describe. Here's a quick video clip I took(you'll really hear the sound towards th end of the clip):



Steps taken to try and diagnose/remedy the issue:

Removed skimmer from sump

Removed pump from the body of the skimmer and disassembled

Everything is pristine. The impeller/drive unit is fine. I didn't see anything inside that might cause an issue

Reassembled the pump, ensuring the drive unit is fully seated into the bearings, closed the pump, and secured with the screw.

Reattached the to skimmer body. The bulkheads on the body look to be fine as well. The internal T-piece is level.

As I found the source of the sound is difficult to pinpoint at first, I thought it might be due to some sort of turbulence within the body, between the water and air. I raised the level of the skimmer a tiny bit and run it to see if that might help. The sound persists.

The sound is also preset with the standard Hydrofoamer configuration or with me running my C02 scrubber. As you will see in the video, the sound starts as soon as the pump it turned on, even before the water column is fully formed, so at this point I believe the noise coming from the pump. If I crank up the pump the noise goes away to an extent, and conversely if I reduce it to the lowest setting it is tamed a bit but still there. 35-40% is where I am running it and where the sound is the worst. There is nothing touching the pump that might cause vibrations either; it is close to the front pane of the sump but there is a gap.

Is this part of the normal break-in process and will eventually subside, or might there be an issue? It shows no sign of stopping.

 

[rvitko]

Tough call, that noise is not like anything I am familiar with, could I see the impeller out of the pump? The main issues that come to mind are:

1) Water coming the air intake, this can be normal, the auto antioverfoaming feature directs water into the air intake to choke it off until the surface tension returns to normal, that is not the case here, the water level in the middle phase chamber is not high enough to be the cause and this tends to make a coffee maker noise.

2) A bad motor, we have had pumps that the motor coil is installed incorrectly, too high, this then causes the impeller to rub on the housing and it makes a sound that could best be described as dragging a rubber gloved hand on a chalk board, kind of a screech, but it is steady, and the skimmer performs badly so you need to be at 100% for it to work at all, I heard no screechy sound and it is very pronounced on start up. Generally this is a problem of the past, they have a QC check for this issue now

3) A not seated bushing will cause a knock, the bushings have to be fully seated, they do not come out without forcibly extracting them with pliers or a hook, they cannot be seated with the impeller, they have to be seated before the impeller goes in, this could be a plausible cause.

4) A damaged impeller, shaft on one end is broken or loose, it sounds like this is not it.

5) An unusual air intake, basically too much or too little air causing a balance issue, if it does this with the factory silencer assembly, I would rule this out.

6) Hard surface contact, the pump does vibrate, if it has contact with the glass this could be a cause, especially at certain speeds as there are certain resonance frequencies that create a more distinct noise, the key here will be to have no hard surface contact, feet installed on the skimmer base, pump not touching the glass, etc.

 

[B-SMOOTH]

Here are some pictures of the impeller and internals








The pump did make an odd screetchy sound the very first time I turned it on and was running noisy. I turned it off and back on again and it was fine. This could have just been the pump settling in. It has not happened since.

As an exercise, I completely choked off the air to isolate the sound. It's seems like a little rattle of some sort. The base of the skimmer is fully level and in contact with the sump on all feet and the point of the filter guard that is attached to the bottom of the pump. I double checked to make sure the pump is not making contact with the front glass.

 

[rvitko]

If it only did it dry on first start up that is normal, the motor issue usually causes really bad performance, since the needle is dragging it barely skims unless running at 100% and normal is around 40% it should skim well, wet even depending on water level. In this case the water level is fairly low, but definitely not too low. I really don't have an answer as I just have not heard this same noise. My only other thought, that grey duct is there so water can get blown up through the bearing and push air out of the top of the pump, if it was clogged, air could get trapped up there and that causes noise, it pries out but is by no means easy, you need a wide flat blade screwdriver to hook under it and pry it out. I think what I would try is see if the pump does this on its side submerged (rule out air in the pump (duct issue)) and then try running it a week, if nothing improves, I think we should try a new impeller, the noise sounds like a knocking like the impeller is moving up and down and the shaft is tapping on the motor which will generally be shaft length or air or bushing fit. Can I get a photo of the serial number tag on the pump cord? This has the date it was made.

 

[B-SMOOTH]

I took the pump apart again, and removed the duct/vent, and made sure everything looks normal. I made sure to fully re-seat it in the pump housing and reassembled the pump. Fully submerged, and on it's side, is seems to run smoothly. No odd noises. Just the standard low hum. I put the skimmer back together and connected the standard silencer for good measure, and the noise is still there. Going to keep running it per your guidance to see if it resolves itself.

Here is the serial:

 

[rvitko]

It has to be the drive unit moving up and down in air, so if the duct is not clogged, it has to be something that is just wear in or a bad impeller assembly, that will come with the bushings. Basically there is something (play in the parts or air in the magnet chamber) letting the drive unit kind of hammer up and down.

 

[B-SMOOTH]

Agreed. Something is probably moving around. I will check back in next week and provide an update.