Planning the next
AO Silver Member
Join Date: May 2007
Location: United Kingdom
Sounds very much like an alternator bearing fault I had.
You could slip off the auxiliary belt and do the same test. If the sound goes away, you'll know the problem isn't deep in the engine and will be a relatively simple fix and limited to : alternator, belt tensioner, power steering pump or aircon compressor/idler pulley ( if fitted ).
You should be able to rule out the aircon compressor ( if fitted ) and power steering pump, by using a long screwdriver. If you have long hair tie it back and keep your hands well out of the way of the belt! With the belt back on, place the end of the screwdriver on the PS pump/aircon compressor body and put the other end to your ear. If either of those components are at fault it'll be obvious. Ruling out the other components is a little more problematic owing to access and the risk of the listening tool encountering the belt. As a simple test and with the engine off, spin the tensioner and idler pulley ( if fitted ) by hand. You may be able to feel a noisy bearing there.