Water pump or crank pulley

[Meir]

hi bala.
i was trying to think what could be the source of the noise, when the belt is off.
hope for you that nothing is wrong with the crankshaft bearing.
the only two moving parts in that area (as far as i know), are the oil pump (red arrow), and the scavenge pump (yellow).
see if you could narrow down the source of the noise to one of them.
this is just an assumption, and i don't want to misleads you.
hope you will end up finding it to be something simple to fix.
good luck.