Boiler pump problems - Very loud when changing the speed

When I go to repair faulty boilers according to the customer - it can be actually not the boiler it self is faulty, but other component in the heating or hot water system is causing the boiler to shut down or not to come at all.
One of the component is faulty pump not circulating the heated water away from the boiler heat-exchanger. such as this video.
Some other components which can cause the boiler not to operate are - 2 or 3 Port Valve, programmer, cylinder-stat or room-thermostat.
If you live in London within M25 and need a boiler service or other plumbing or electrical service, book us by calling 02082008580 / 07974711639, or email [e-mail] . Please visit our Website www.unicuk.com to see our other services and charges.

[@ksmith7122]

I get the exact same noise in hot water circuit pump (not rads pump) in combi boiler. Is it an air block/ lock in pump? System depressurised over time and problem began after repressurisation. Pump was very hot (though not dangerously so) and noisy and so I turned everythnig off and let it cool down. Hot water pump now works intermittently like the one in the video. It's set to III. Sometimes it works quietly. Smoetimes it howls noisily. Anyone ideas?

[@JunglistLDZ]

Hi K Smith,
Got the same problem ,
Did you fix your pump ?
Thankks

[@petersutton3054]

Pumps running dry it's fitted face up causing air lock

[@mrbachittarsingh9243]

Peter sutton wrong, it's the pcb