(21 Jul 2014, 12:35 pm)G-CPTN wrote ISTR hearing this sound (compressor air system pressure venting) when the Citaros were operating on the TEN and being told it was 'normal' (as a retired vehicle engineer I didn't agree).
The system should vent when it reaches full pressure, but (in my experience) isn't normally so audible unless there is a fault. Not all Citaros made this noise, otherwise I would have accepted that it was normal.
This noise was around the nearside front wheel, so probably something to do with the kneeling function.
GNE 6081 was making the same chuffing sound from the area around the nearside front wheel whilst waiting on the stand at Hexham at 14:20 today.