I'm getting a really loud occasional roaring of the engine above 2200 rpm. it happens through all gears and continues to the redline. Sometimes it will ease back into regular engine sound, and when it does this it almost feel as if you were feathering the clutch as when it catches I can feel it pull a bit and the power picks up.
'01 4.0, manual, above 2200 engine noise doubles, sounds as if an auxillary fan (which it doesn't have) kicks in. Jeep still accelerates but not a clean as below 2200. At times, around 3500 the noise will slowly stop and return to regular engine sound.
A few have mentioned the fan clutch being bad. Not sure if you're aware how to check or not. Normally (I may not be completely right)how I check is while its not running I grab the fan and spin it. If it spins very easily, or if it has play (front to back) than its bad.
Just thought I would mention my .02 cents since nobody said how to check.
How I figured out mine was bad was pretty easy. I had the engine running, opened the hood and shut down the engine, before the fan quit spinning it was squeaking as it slowed to a stop! [img]images/icons/smile.gif[/img]
For anyone interested, spoke to someone at the dealer that actually drives a Jeep, and his explaination was this was caused by engagement of the "fan clutch lock" which engages the fan at a certain temperature and keeps it engages at a higher speed until the engine cools sufficiently. which would explain the occassional occurance. Unfortunatly this is a temporary loss of 40 h.p. until cooled off enough. Anyone put an electric fan on an 01 tj yet. Any thoughts on these setups?