Originally Posted by BrianBrave
Perhaps as the system is building up PSI - enough pressure is made and a leak is occuring. As PSI bleeds - the sound goes away and the cycle begins again.
There have been a few VIDs of folks having pulley/bearing issues and you can hear the grinding through the entire RPM range - your sound seems to start after the SC engages and has some time to build PSI. Just a thought.
With the car parked and at idle - spray liberal amounts of carb cleaner around the plenums flanges and listen for a change in RPM - one way to detect a leak..
I used the carb cleaner spray back in the early 70's. It's a time proven technic for vacumn leaks. Don't see that it would be effective for finding pressure leaks. Just my thoughts! But,Is it harmless to the teflon coatings of the NeedsWings Mani's? Squirrel Crusher