Hi all, I have a hissing sound from behind the dash when I turn off the engine.

I assume its the vacuum reservoir or climate control (lol) manifold but on inspection all seems well, no pipes broken or hanging off? I may put the air line on the main feed pipe from the engine (on low pressure) to see if I can find a leak.

Engine idle seems ok so not suggesting a vacuum leak, anyone have experience with this problem? any suggestions gratefully accepted.

The only two sources of such a noise are the A/C refrigerant lines (assuming you were using the A/C when you turned the car off), or as you guessed, air leaking into the vacuum system that manages the air flaps.

Sometimes you can isolate where in the system the leak is by toggling the floor/demist/recirc buttons. If it only leaks out for example when you have the recirc button pressed, then you know the issue is the recirc actuator/hose. The buttons themselves are air valves so they can also be the source of a leak.

Thanks James, no A/C on at the time, or any time, as it's cactus! needs a compressor if anyone has one? I will try toggling the controls to isolate.