Hi,
I know it is not easy to diagnose noise by description but some hints would be good.
'89 240 with b230k, 185.xxx miles.
I am hearing a sort of metalic whirring sound at tickover, it does not seem to change pitch as revs increase and is less noticeable with higher revs.
The closest comparrison sound is the water just starting to boil in my coal fired heating system.
It does not change with engine or outside temperature.
Thanks
Keith