6040 with Loud Rattle

[PrangeWay]

One of my 6040's has a very loud rattle at 100, and a light rattle at 30 (the other is silent).

I don't see any problems with the vibration damper or magnets so would replacing parts 5/5a (Drive Unit, other inner workings) be the way to go or could it be another issue?

 

[Breadman03]

Have you checked the cables yet? I had some 6095’s and found that a cable was vibrating against my tank rim.

 

[rvitko]

The cable vibrating can be a cause, but I would check that metal shaft is rigidly fixed in the motor, that there is no hardsurface contact i.e. the pump is directly contacting a stone or the glass on the side. I would then try swapping the drive unit between the pumps, if it follows the drive unit, replacing it will fix it. Grit and sand can grind down the inner surface of the hole that spins on the shaft and create an eliptical rotation that makes a lot of vibration and noise. In some cases, the cause is the deflector/flow path, for example the flow is bouncing back and creating a lot of turbulence that results in the propeller bouncing around.

 

[PrangeWay]

Adjusting the flow path took care of the low-end rattle. Will do some drive unit swapping to see if it needs a new one, as the noisy one is an original/first run production 6040 so it is well used.