I am getting what sounds like some kind of rotational grinding noise coming from the front end. I hear it at idle when the engine is first started but after a few minutes it can't be heard at idle (or is at least very quiet), only when RPM's are increased. I have had this happen before but the noise went away. It seems to be the worst/loudest around 2k RPMs. Timing belt and water pump were replaced about 4500 miles ago and I did an oil change last week. I know diagnosing engine noise without hearing it in person can be difficult but any help you guys can offer would be greatly appreciated. Thanks in advance!