I have an '89 240 wagon that emits a hissing sound from the center console whenever I shut the engine off. I was concerned about there being a vacum leak so I took apart the console to check the heating/ac system. All of the vents (defrosters, heaters, recirculation vent) seem to be operating properly and the vacum hoses seem fine.

I suspect that the sound I am hearing is the vacum tank venting. Anyone else experience this problem?

 

My dad had a subaru that did that its whole life, its just what it did and it ran/worked fine the whole time he had it. If everything works, its probably nothing to be concerned about, but I'd keep an ear on it to see if it get worse. If you wanted, you could start clamping off hoses to try and track it down. hope it helps

 

mine hisses too. I have been too lazy to hook up the hand operated vacuum pump to see where it is coming from. I suspect one of the vacuum actuators for the heating/ac system is leaking

 

I did some experimenting by clamping hoses. The only one that seemed to have any effect is if I clamp the main vacum feed coming from the engine (which makes sense). When I clamped the hoses running to each of the controls (floor heat, defrosters, recirculation), it still made the hissing noise.

Do you know if there is any bleed valve that may be releasing the vacum once you turn off the key?

 

I beleive it is just noise from air flowing through the Air reserve tank.

 

My 89 740 makes the same noise and always has. The heater and air conditioner have always worked fine as well. Just chalk it up to a normal noise that may be abnormally noticible??

 

The only reason I was concerned about it is that I have had the car for over 12 years and it just developed the sound recently.

If my memory serves me well, I think it used to make this sound when I shut the car off only if I had been using the AC. Since the AC hasn't worked for 10 years, I could be mistaken.

I'm not going to lose any sleep over it since I have ruled out any vacum leaks.

Thanks for all the help

 

For anyone who is interested, I found that the problem seems to be due to a check valve mounted on the intake manifold. It seems like it is supposed to keep the vacum tank under the dash from losing its vacum during acceleration and when you shut the engine off.

Now I need to just find another valve.

 

Thanks for the update.

 

Thanks I will check my "hissisng valve" too!