Dull knocking comming from steering system
I hear sometimes some weak dull sound/knocking comming from left under side of dashboard when I am driving over some holes on the road or if I am turning steering wheel left to right in a fast short movements during the ride on the even road surface. When during ride and steering wheel movements the knocking is just like there is some clog inside something which knocks left or right, the rattle is not synchronized directly with my movements.
This knocking is present only when I drive up to approximately 80km/h and it's hardly hearable on the cold mornings and much more present if the car is hot. The knocking is present a few months sometimes more and sometimes less.
I isolate the knocking to steering system, because I hear it also when I am not driving and turning the steering wheel left to right in fast short movements.
The knocking is not noticeable so much, some wouldn't even notice it, but I am going to a larger round trip for 5000km and would like to know before journey if this is something serious. Which part of steering system could it be?
Thank you in advance!
P.S. The car normally passed MOT test last week.