In this case a 3 ft. piece of garden hose, heater hose or something like that would probably work better than the stethoscope. Taking the belts off might help eliminate some things but probably wouldn't need to if you use the hose.

__________________
1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)