2000 2.7L - hissing noise??? what is it

[23109VC]

i've borrowed my dad's car a handful of times over the past few months. each time i drive it, i have noticed at low speeds, with the top down, when I am backing into and out of parking spaces. and the engine is revved, but at low speeds / rpms... i can hear what soundsd like a hissing sound.

to me it souns like air spraying out of a hose. or like if you took an inner tube in the water and it had a small leak and it was leaking.... pssss psssss

hard to describe sounds let alone describe them with words... but that's exactly what it sounds like. air leaking out a tube...

i have told him about it a few times, but he's hard of hearing, and I hoenstly think he just cant' hear it and figures he'll deal with it next time it's in for service.

is this some common issue and someone here knows what this is? hopefully something he can fix easily / cheaply.. and not some possible catastrophic problem.

the car seems to drive fine - probably partly why he's not rushing in to fix it.

when you have the top up you an't really hear it and if you are driving normal with the top down, you can't hear it. it's really only audible if you are stopped, top down, and slightlyh rev the motor..as you pull away..or if you are inching into a parking space and modulating the clutch/gas...so that you are slightly revving the car and not really moving that fast....you can hear the pssss pssss sound as the engine revs. i don't recall if it does it much at all when you are just idling.. it's more when you give it some gas...

anyone????