Metal Baloon (Balloon) sound

[Chamberpains]

What you described is exactly the noise that is made when the turbo mounting gasket is leaking. Someone either misinstalled it or did not torque the bolts properly. There are Two Nuts and two bolts ( 4 total) usually that hold a turbo on. More than likely you need to get your torque wrench and socket out and torque them down properly. If that does not fix it you will have to pull the turbo off and put a new gasket in it. Login to Cummins quick-serve and register your engine serial number then look up the proper torque spec for your turbo mount.