i have a 98 accord. while the engine is off and press the break and hold it, i hear a almost squeaking noise comming from this hose top/near the break fluid res. this hose runs into the engine manifold. i can feel the vibration of the hose to determine that the noiise is coming from there. what is this hose for and should it be making that noise? another noise is i put the key in and turn it to the on position and then i take out the key and there is this depressurising noise like a turbo swish but no so loud coming from that area of the break res. what is this noise? thanks

 

Power brakes use engine vacuum to assist you in braking. The hose you are talking about is most likely the one that delivers vacuum to the power booster. Since engine is not running you probably releasing the left over vacuum.
I think this is normal.
I have never tried it though.

Sam