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Hi all, whenever I've been starting my 4.0 in the cold (around 0 degrees) there is a loud high pitched whining noise that comes from the engine that intensifies/gets higher pitched as rpm's increase. What could be causing this? Doesn't sound like a belt. It goes away after a few miles
 

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Possibly the alternator or a bad pulley.
 

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Possibly the alternator or a bad pulley.
It isn't the alternator because I replaced that recently and it made the noise even before it was replaced. I took off the belt and started the truck and it sounded a lot more quiet, leading me to believe that it is a pulley problem. I put the belt back on and watched all of the pulleys for any movement/play, and the water pump pulley wobbles a bit, and the tensioner kicks/bucks a bit. I took off the belt again and spun the tensioner pulley and it has a lot of play, so I will be replacing that bearing. I also checked the harmonic balancer after hearing about how prone they are to failure on the 4 liter engines, and it is solid as a rock and spins great. With the belt on again, and the engine running at operating temperature at idle, I can push a rolled up newspaper into the hub of the radiator fan and it stops with little effort. Could this be related? Thanks
 
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