Hi, I am new to the forum and after reading a lot of posts and answers on here i am sure some one can help, hopefully, i have a mondeo 2008 and lately i have noticed when the car is running but stationary at the lights or something i hear a hissing noise on the drivers side could be air, when i press brake pedal firmly it goes, also there is another strange noise the only way to describe it is like when you open and close your mouth like a fish and you get a kind of bubble noise, i also only hear this when stationary, any help at all to put me in the right direction on what action needs taking, sorry for the fish description.... thanks

if hiss appears to be coming from inside car, could be the seal on the brake servo, have come across this loads of times on galaxys, but could be the same with mondeo..

need to put your head under the dash, look for the point brake pedal rod enters the servo..there is a seal, if your lucky you might find its just popped out, if so it is possible to reseat whilst in situ, but can be very fiddly...more often than not, lot quicker to remove the servo from car.

not sure if seal is available seperately, as i normally end up being asked to fit 2nd hand servos as it saves time and money.

if hissing from under bonnet, going by it stops with press of pedal, then still expect this to be servo/servo valve/hose related...just need to trace exactly where hiss is coming from

thanks for the info wase16ll , will have a good look round tomorrow and see if i can pinpoint the noise.