Vectra M1 whines after cleaning

[chema]

I have had a Vectra M1 as return pump for almost two years. It was working nicely and pretty silent at around 60% of the power (I don't need more). Ten days ago I removed it for cleaning. Disassemblied it and gave a vinegar bath for 1 h; afterwards I mounted it again. After putting it into service it has been making a whining sound even when ran at 40%.

Any idea how to solve it?

 

[Waters]

That is why I don't clean mine lol. I would just try taking it back apart and reassembling again. Maybe something isn't seated properly?

 

[chema]

I’ll try that. But the whining sounds like the motor itself and not something that is not seated properly.
I remember that when I put it into service I could hear some whining, that disappeared soon as far as you didn’t push the power more than 60-70%.