When I turn on my air conditioning it sounds like a jet is under the hood. I have a 528i xdrive
It doesn't matter what the temperature is, when I turn my AC on, it gets so loud that it sounds like a jet is under my hood. Is this normal for the 5 series sedan?
Probably just the cooling fans running.
Normally cooling fans run when u turn on the AC. Unless it's a squeaky noise it's normal for cooling fans to turn on. Open the hood and watch the cooling fans kick in while someone else turns on the AC and see if you can pin point it out.