Whirlpool UK dishwasher making a funny noise at start of cycle

[andyr123]

Hi, all - i got a nice Whirlpool UK Model Dishwasher second hand , washes lovely works absolutely fine (apart from the auto door opener which i can deal with I just open the door manually) - the odd thing though is the noise it makes after the tub fills up with water at the start of the cycle. Sounds like a trumpet/Tuba then machine Gun lol thats the only way I can describe it. Only at start of cycle and then does not appear for the rest of the cycle all you hear is the normal filling and sloshing a dishwasher makes as its working.
Just wondering what the noise can be - I dont think its the fill valve that seems to be opening and shutting OK , and I dont think its the pump because when thats pumping out its quiet and when its washing its quiet so I dont think its the wash motor - but what could be causing that strange noise! ?

Model number is: WFC3C33PFXUK and it looks to be an Hotpoint/Indesit made model - similar to the Hotpoint
Hotpoint HFC 3C26 WC B UK
I have done a video here and bumped up the sound on the video a little bit:

 

[foxhole]

Sounds like pump cavitating when empty or fouling on foreign object against pump

 

[andyr123]

Sounds like pump cavitating when empty or fouling on foreign object against pump

thank you. But machine is filling up with water as it starts cycle, so it wouldn't be emptying water out

 

[foxhole]

thank you. But machine is filling up with water as it starts cycle, so it wouldn't be emptying water out

DW always pump out at cycle start .

 

[andyr123]

DW always pump out at cycle start .

Thanks. It pumps out yes at very first and no unusual noise there, just normal pump noise. It then fills up and just before it starts the cycle it makes noise , and then for rest of cycle even when it pumps out there are no strange noises just normal ones.

 

[andyr123]

I am wondering could it be that air box thing /air break on the left hand side of the dishwasher at the bottom making the noise. is that a possibility? or maybe the salt regen container? - i am most probably clutching at straws but it has me baffled.