another post about my adventures to get rid of small noises of my 146 1.6ts facelift
I know it's common problem, there was a creaky noise from dashboard, usually on bumps but more in general when there was any movement/torsion of the body of the car (strong bends or accelerations etc.).
The sound was clearly of plastic on plastic, and coming from the windscreen vent plastic cover.
Solution was actually to take off the cover (it's just fixed by simple hinges and comes off easily), I've put a small thin layer of bluetac all around dashboard border, but just on the uper side (towards the engine), to avoid the plastic/plastic contact and keep the vent cover more in place. It's all under the vent so it's not visible, it's easily removable and cannot go anywhere.
To make the cover even more stiff in place, I added some chair legs felts (cutted to be very thin) on the other side, pushing gently this way the vent against the other side with bluetac.
Tadaa...problem solved, now silent and the cover seems in place much better than before!