Spot that noisy pump

[ant2]

Pump started making a horrible "whirring" noise. Been increasing in frequency over the last few days. Last night it was doing it 90% of the time over 7 hours.

Pump is 3 months old, if I set the head to 2M the sound quietens down, I believe that's only due to the rotations being less.
Noise "blip" can always be heard when it first spools up (sounds like the start of a slipping drivebelt), seems luck of the draw depending on the first spool if it will start to "grind", but over the last few days each spool is more likely to incur said "grinding"

Sounds like the propeller starting to scrape on the side or dodgy motor?
Decided to order another one to swap out, but out of interest wondered if anyone had any ideas on the fault

 

[snb]

sounds like some debris stuck in the impellor combined with a lack of water in system( or partially blocked cold feed)

 

[ant2]

sounds like some debris stuck in the impellor combined with a lack of water in system( or partially blocked cold feed)

Any suggestions how to get it out?
When I spoke to DAB there's no screw to bleed air, they suggest putting the pump on max to blow it out.
I had the pump on max (8M) for hours and didn't get any air out of the rads/vents.

Drain the whole system down and rinse out the pump?

 

[snb]

undo the 4 allen keys and you will see the impellor. you can then remove the head from the valve body.