Originally Posted by javierb14
the oem bearing in the pulley is a NSK. the part # on this bearing is 6301DULX. any good auto parts store can cross reference this bearing and find a replacement for much less $ than the complete assembly.
True enough, but my ne SKF replacement number 6301-2RS1 ended up making the exact same noise. I'm waiting for an explanation from SKF. Will post any answer.
The only comfort in having a brand new noisy replacement bearing is the knowledge that if nothing else is wrong with it (ie: its noise is not a sign of any defect), then I should be able to look forward to another 8 years of use from my idler pulley with its SKF bearing.
The other possibility is that the original NSK bearing that I personally replaced was not the original source of the noise, and the replacement SKF bearing is not noisy either, and that the mechanic at the Nissan dealership who claimed that my replacement bearing was noisy had made a mistake in believing that the noise is coming from the idler pulley and not the alternator or AC.
The big problem in identifying the source of a noise coming from a pulley on any drive belt is that all the pulleys may turn smoothly and quietly when turned slowly by hand with no belt present, but as soon as you attach the belt and put it under tension and spin all these pulleys at several thousand rpms, it becomes very difficult to determine which pulley is squealing. My Nissan mechanic used a screw driver between his ear and each accessory and claimed that the idler pulley bearing was much louder than the alternator or AC bearings.
Another thing is to be prepared to have your original bearing potentially damaged as you press it out of the pulley. Unfortunately this bearing resides in a cup and the hole on the side of the pulley that gives you access to your punch is not as large as the diameter of the bearing's outer race. So when you insert your punch (I used a ratchet socket), the punch will either press against the inner race only, or as in my case ,against the bearing's plastic grease seal. Either way, you are not shielding the balls from the lateral stress of the punch, and that has the potential of creating flats on the balls of the bearing that you are removing. So be forewarned to not count on putting the old bearing back into place should the replacement one not provide any improvement and you want to return the new one.