thanks.
Eventually the noise will occur while AC/heat is running at various speeds. Unless you leave the tube clamped off at the grey box(reservoir). Also the actuator gets its supply of vac from the solenoid, also right there by the grey reservoir,, if you follow the green hoses; this one has to be clamped off as well, if the leak is there. I havent replaced the actuator, (everything works for me, including the cabin air door,as for you, )due to hand surgery that precluded cramming myself and hands up under the dash. Ive had glovebox out for three months now, while procrastinating the actuator replacement. Problem is that actuator has a spring and is tucked up in there, so I know I can get it out, but unsure about getting the new one in. Final plan is to clamp off as you did. One caveat is that it is very hard to tell where the noise is coming from under there. Clamping at different places, and then driving for awhile makes the diagnosis.If your door is stuck closed, no fresh air. If its a convertible, hardly a problem....
Cheers.
BTW the grey reservoir is just for the cabin door; It doesnt have any function for the central locking sysytem