hi all i have a skoda octavia 2008 vrs . when the engine is running  you can hear a air leak inside the cabin.
i have looked behind the dash and the air rush is comming from just behind the push rod on  brake servo .
when i press the brake peddle the air rush goes away until i release brake peddle then the air rush comes back. 
Just wondered if this is normal as ive asked a local mechanic and said my brakes are ok and working as they should.
but am a bit worried about the air rush.

it should draw air in at that point BUT  (from memory) only as the brake pedal comes up    flowing all the time suggests there is a sticky valve inside  the servo   take alok at a how does it work vid' on utube and it should become  apparent what's happening   I would have thought that a constant flow will weaken you mixture off

Edited 19 April, 20188 yr by cheshire_cat
addition

Thanks i will check that

I think you should only hear air entry into the servo when the pedal is pushed.

I always worry that when I press and hold the brake pedal at a standstill, it gradually seems to sink towards the floor. Un-nerving but it seems to be the same in all servoed cars I've owned IIRC.

Doesn't happen on the move, so why when stationary?