Vibrating buzz noise from Grundfos 15/50

[PJBN]

Hello

Our central heating water pump has recently started to make a loud vibrating buzz whenever the thermostat kicks in the central heating.

It lasts for up to 10 secs before dying away to nothing (but it's waking my lad up as it is in his room).

Is there an adjustment I can make to the pump settings ?

I notice there is a big silver disc on the front with a notch in it, but I have no idea what it does.

There is also a thing on the left hand side that looks turnable but I don't know what that does either.

If it means anything, we have a big black plastic tank in the loft and a secondary smaller tank next to it, both overflow into the same outlet pipe.

Any help welcomed - thankyou.

 

[sotal]

The black switch is the speed setting 1, 2, or 3.

The Silver bit is the bleed, to allow air out.

Put a bowl underneath and unscrew the silver bit with a big screw driver.

I think the instructions said to switch off the heating, then remove the silver bit, then switch the heating on. It will drip slowly from that hole and will release any air. Once done, switch off the heating and replace the silver bit.

 

[PJBN]

Thankyou for your reply.

If I remove that big silver bit off the front, and turn the heating on such that the pump starts up - I take it I wont get boiling water spewing everywhere ?

Is it just like bleeding a radiator? When do I screw the silver bit back on again ?

Will this cure the loud vibrating noise I get when the pump kicks in ?

It lasts about 10 seconds and is pretty loud - then dies away and seems happy.

Heating works fine.