Grrundfos Pump Intermittent Failure & Very noisy

[kez1]

Background I have a Grant Vortex 36E Oil fired boiler. Two Grundfos pumps inside; one for the rads & one for the hot water.

The Problem The pump on the hot water circuit is making a howling noise when I run hot water. But not always. The hot water pump has, and as far as I know, always has been set to the max pump rate III (I & II are the other pumping options on the side).
I used a coin at the back of the pump (first photo below) to release any possible air trapped and then tightened back up again. I couldn't detect that any trapped air was released as I did this.
It's still making the same howling noise when water flow demands pumping, though, as I said, not always.
If I turn the pump rate, on the side of the pump, down to II or I when a hot water tap is running, the pump goes silent and sounds like it stops pumping and the hot water eventually runs cold.
Sometimes the hot water pump works properly and does not howl, and delivers hot water, other times it howls and does not pump.

Scroll forward to 1 min 2 secs to hear the howling sound my pump makes.
The video does not show my pump though the photos are my pump.

Question Is the pump servicable?

Photos attached

 

[muggles]

They aren't serviceable but you can purchase replacements

 

[kez1]

This is the sound I get.
You can hear the sound by scrolling forward to 1min 2secs.
This video is not of my pump though the photos posted are.
Read more: https://www.diynot.com/diy/threads/...tent-failure-very-noisy.504492/#ixzz5IrYyQGmP

 

[muggles]

My response hasn't really changed - new pump needed

 

[shambolic]

Also fitted wrongly as it should horizontal

 

[muggles]

Also fitted wrongly as it should horizontal

I nearly fell for that one, but the video is just a pump the OP found on YouTube, not their own one!