Heater Control Valve vacuum?

[zapp240]

Question, should the Heater Control Valve hold vacuum after engine stops , have a pretty loud vacuum bleed off sound after I turn car off coming from the valve, is that normal never noticed it before. last for about 8 seconds

 

[salvageV6]

Yes it needs to hold vacuum at the diaphragm.
It should make the same noise when idling if it is leaking, does it?

 

[zapp240]

thanks SalvageV6, my car idles pretty loud and i can't hear it untill it is off. am going to run a rubber vacuum line to it and see if i can get it to hold vacuum with my hand vacuum pump.