Hissing sound when engine running - even at idle..

[dave944-87]

I seem to have a "hissing" sound coming (not loud) from the 944 when I drive it, and still when I idle. It is difficult to tell where it is coming from.. sounds like it may be underneath the car.

I have noticed that the car smokes a little more than normal from the exhaust.. I'm pretty sure it's not a broken hose as most of them they have been checked/replaced recently.

Any ideas? Could this be a transmission issue perhaps?

[TCMdocs944]

Vacuum leak?

Balance belts normal whine?

Are you having any other symptoms or just the hiss?
If your idle is high (over 950) it is probably the vacuum

[fast924S]

AHH, I hate noises like that, I still am trying to find a hissing metalic rattle that only happens on decel, I have been chasing it for 2 years. Good luck. It might be a heat sheild or a exhaust leak

[dave944-87]

Everything else seems ok.. but when I drive down the road I don't sound a smooth porsche!

It's loud as in you don't hear it in traffic or busy area, but if you drive down a quiet residential street it is quite noticeable.. (oustide the car).

What's the "balance belts normal whine?"

[fast924S]

Kinda sounds like a light supercharger wine

[dave944-87]

Well, it's not a turbo..?