so I've been noticing a hissing noise recently when I shut teh car off and have been trying to track it down. Hoping someone with more experience can offer some insight.

In the engine compartment the hissing noise appears to be coming from a little valve thing that looks like the fuel pressure regulator and sits in the middle of one of the two coolant hoses that go into the firewall. This would be the heater valve, correct? Does the hissing mean it's shot or is there something else at work?

On the cabin side the noise appears to come from behind the climate control board. I pulled the board to take a look and it was noisier once I got it open, but I couldn't find anything that appeared to be the source of the noise. Kinda tough to tell since its a pain in the arse to get past the control console (no slack). Is it possibel the noise is a byproduct of the engine compartment/heater valve hiss, or is this something else. I seem to remember hearing the engine compartment hiss first (before teh cabin hiss became apparent), so is it possible a shot heater valve killed a related product on the cabin side?

Any help is greatly appreciated. Thanks in advance for all replies.

-rt