Nah, it's not sounding high-pitched enough - as silly as it sounds, that's how I know something was starting to go, and it was from the overfuelling where oil had leaked into the coolant system, effectively causing it to overfuel, I think that's due to the temp sensors not being able to correctly read the temp due to the sludge in there.
Should sound like this, it's not much of a difference but there definately is one:
http://www.youtube.com/watch?v=T_wdsR2rB0o
Might just be worth having a check
