Hissing behind Center Console on Power Down
 

Hello All,

Does anyone know why a hissing sound might be coming behind the center console of my 300D?

It doesn't happen while the car is on, only for about a second or two after I turn off the car. Sounds like air. Is this normal?

Notes:
The AC works great, the center vents kick in after the car is on and aren't engaged when the car is off.

Your efforts in helping me put this to rest is much appreciated.

-Ian

You're right in checking the vents. The only thing back there that could make this kind of noise is a vacuum line or associated actuators - leaking.

Gold Vacuum Elements
 

Thanks..

There are a number of different Gold vacuum relays behind the center console. The sound comes from one or more of those.

On the one that I think might have something to do with the air leak noise when I bypassed it, the car wouldn't shutdown.

Is there any way that they need to discharge air in order to shut down the engine?

Should I just replace these relays?

-Ian

OK Ordering Parts
 

OK. So the sound went away when I put my finger on the bottoms of the Vacuum Change over relay valves. Thinking that this isn't part of standard operation, I ordered some new ones in the mail.

Ian