Idler Pulley Bearing Replacement Info - Nissan Forum
GA16DE 1.6L Engine Engine Discussion: 91-99 Sentra, 95-98 200SX, 91-93 NX1600

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post #1 of 5 Old May 16th, 2003, 01:34 AM Thread Starter
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Idler Pulley Bearing Replacement Info

for those who ever have an idler pulley fail, u can replace it with a new bearing rather than buying the complete assembly from the dealer. 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.

bad NSK bearing that causes the engine to throw belts!

OEM idler pulley assembly from dealer

PTC cross referenced bearing from auto parts store

basically u remove the idler pulley and press the old bearing out with a hydraulic press and a socket or something similar. make sure u have it on the outer race of the bearing when u remove the old one and install the new one. reinstall everything and the car is good as new

Anything else is half fast!
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post #2 of 5 Old May 17th, 2003, 11:46 AM
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Looks like a normal bearing from a skateboard or rollerblades. You can get 8 ABEC 7 bearings for $30.
post #3 of 5 Old May 17th, 2003, 02:41 PM Thread Starter
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it could be. an ABEC 7 bearing would definitely work in this case, IIRC they are rated for about ~30K rpm and have tight tolerances. what i forgot to mention was that u cant get just the bearing from the dealer, u have to buy the whole assembly.

Anything else is half fast!
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post #4 of 5 Old Oct 1st, 2006, 05:58 PM
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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.

Last edited by montreal-1; Oct 1st, 2006 at 06:06 PM.
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post #5 of 5 Old Oct 4th, 2006, 01:23 PM
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After three days going by without an e-mail response from SKF, I telephoned them to again ask if it is possible for a brand new SKF bearing to be as noisy as an 8 year old NSK bearing whose noise just started last month.

The CSR engineer doubted that a new SKF bearing that could be defectively manufactured or damaged while being installed would generate a high pitched squealing sound. He said that when the balls in bearings have been damaged by pressure from a press being improperly applied to the bearing during insertion, then the balls can acquire flats on them but the sound generated by a small ball with a flat rolling in a deep grooved raceway does not generate a high pitched squeal.

He said high pitched squeals tend to come from dry metal parts scraping across other dry metal parts, as would be the case from a bearing that had lost its lubricant and where all the balls had seized up and the high pitched sound would be generated by the frozen metal components scraping on each other.

But where we have a case where the bearing is not seized but spins freely as was the case with my old and new bearings, then it is unlikely that either bearing would be the source of the high pitched sound.

The mechanic at my Nissan dealership concluded last week after placing a long screwdriver between his ear and the different belt driven accessories, that my idler pulley was making the loudest noise compared with the alternator and AC. Maybe the loudest noise he heard was indeed coming from the idler pulley, but was the noise travelling up his screwdriver really the same high frequency airborne noise that I hear with my ears, or was it a different lower frequency noise? Or could that thin metal disk that forms the dust seal over the exposed side of the pulley be induced to vibrate like a loudspeaker and generate that high pitched metalic squeal even though nothing may be actually rubbing.

I don't regret changing an 8 year old idler tension pulley bearing that may not have needed replacement. I have bought another 8 years of reliability. But I do regret that there still appears to be an accessory attached to my drive belt (probably the alternator) with a noisy bearing or some other dragging metal part.

I suppose I could start by pulling my alternator apart.

Last edited by montreal-1; Oct 4th, 2006 at 01:59 PM.
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