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DIYfrvr
User
Jul 1, 2013, 10:50 AM
Post #1 of 9
(2695 views)
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Grinding noise
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Needed some opinions on debugging a grinding noise from the engine bay.
Sorry for the long post - you can just read the sections in blue for a shorter post.
Description
I don't have a video yet - best way to describe the noise is a grinding noise from the engine, specifically, the side where belts are located. The noise goes away and comes back every 5 minutes or so. The noise doesn't occur as much once the engine is warm. It gets louder as the engine speed is increased.
Debugging (here are the steps I've followed so far) - When I used a stethoscope to listen to noise by the timing chain cover and alternator, it was significantly louder when I touched the alternator.
- Since it was louder with the alternator, I decided to the remove the AC belt (in this car there are two belts - one runs the PS pump. The other runs the Compressor and Alternator). Once I removed this belt and turned the car on, the noise went away.
- So I assumed that the noise must be one of the three: idler pulley, alternator or compressor. The noise doesn't increase with the AC on so I ruled out the compressor. The alternator was replaced less than 10k miles so I ruled that out. I'm left with the idler puller and tensioner assembly.
- (Worth mentioning that with the belt off, I spun the idler pulley, alternator and compressor and did not hear any noises)
- I'm going to replace the idler pulley and see if that fixes the noise.
Question
This car doesn't have a spring loaded tensioner. Is it a good idea to replace the idler pulley assembly including the tensioner or can I just replace the idler pulley? Thanks!
Car details/maintenance background
2001 Nissan Maxima 3.0L with 160k miles.
Both AC and PS pump belts have been replaced 2 years/20k miles ago.
No timing chain service was done. Guides and chains are original.
Idler pulley is original - never replaced.
Alternator replaced within 10k miles.
Oil changed - Mobil1 with Bosch distance plus filter
(This post was edited by DIYfrvr on Jul 1, 2013, 10:51 AM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 1, 2013, 10:58 AM
Post #2 of 9
(2685 views)
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Re: Grinding noise
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Sorry if I missed it but you already did what you do for that and it quit with belts off so then you spin items and it's usually pretty easy to determine which is the culprit but may take an experienced hand.
New alternator means little. I doubt rebuilds put new bearings in them or some anyway and new cheapo Chinese bearing fail horribly or can last.
If you determine alternator bearing those can be done alone without another alternator but takes some know how or if under any warranty go for it,
A belt driven anything shouldn't be that hard to diagnose but helps if it's bad enough you can just feel or hear it, belt(s) off,
T
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DIYfrvr
User
Jul 1, 2013, 11:01 AM
Post #3 of 9
(2678 views)
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Re: Grinding noise
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Thanks Tom. Really appreciate the fast reply.
Quick follow up - if I'm replacing the idler pulley, is there any merit in replacing the tensioner as well? Just trying to avoid taking apart more things than I have to and since this is not a spring loaded tensioner, I figure it probably doesnt go bad.
(I will now look into the alternator warranty as well)
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DIYfrvr
User
Jul 1, 2013, 11:05 AM
Post #4 of 9
(2672 views)
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Re: Grinding noise
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Also, could you tell me which brands are best for the idler pulley? Thanks
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 1, 2013, 12:45 PM
Post #5 of 9
(2642 views)
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Re: Grinding noise
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This is where even tech's may differ. I say a good bearing (I think we have a bearing noise going on with this) is good and no known life expectancy. Troubles come when and no offence to China in particular can make, box and ship duped bearings cheaper than the box cost from a good old bearing maker!
In that, I would just replace the bad item. It could be the alternator already.
Since this is not self tensioned bearings don't like being way too tight - that much is true. You should just feel something in spinning an alt, idler or pulley of a tensioner. A/C compressor bearing will either be a noise or feel that totally changes when compressor is engaged or not. When those are not engaged the clutch pulley really is just a pulley and the rest just dead weight! When operating that clutch bearing isn't in use but rather shaft bearing inside compressor are.
Spinning a bearing such as these short of some rubbing possible for A/C they should be silent. No noise, nothing to feel for play or grit feel at all and used ones should coast freely. New ones won't till used a bit.
A new belt is probably in order or both and quality counts with everything. So far no problems with NAPA belts made by who knows.
Whatever parts outlet you choose ask the country of origin of the parts. If they don't know the box should say!
High chances are your alternator was rebuilt so no telling what was wrong with it before that or what quality bearings were used - you just don't know anymore.
In short I suggest just the one that's bad and ask for the best at place of your choice. What it came with new was usually the best so even replacement dealer parts may not be any better for stuff like this and naturally cost more.
Your call on how much to replace while you are there and how much things cost in what could be preventative or fair earlier as said.
Belt if perfect and known age your call. If new it should be checked for tension after it's been used a bit as they do wear in some quickly and stretch a bit.
Other: Belt(s) can make noise themselves just shinning up the belt and the pulleys. If so a mist of water, WD-40 on them will shut one up usually.
If you do suspect alternator and not a warranty deal let me know if you want to replace a bearing in one. Not so impossible but not so easy to explain either.
You WILL find the bad one as it's making noise. Just keep trying as you have,
T
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DIYfrvr
User
Jul 4, 2013, 7:32 AM
Post #7 of 9
(2603 views)
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Re: Grinding noise
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Thanks guys! Issue was the alternator as you had pointed out. It was under warranty so I saved the 80 bucks id have wasted on the tensioner.
Also wanted to add that when they tested the alternator on the test bench, it didn't make any noises. I guess it wasn't as heavy a load as the car. But the pulley did spin in a funny way ( it was rocking ) so the store replaced it no questions asked.
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 4, 2013, 7:35 AM
Post #8 of 9
(2597 views)
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Re: Grinding noise
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Glad to hear it worked out.
Closing this question now as solved to keep spammers out.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 4, 2013, 9:11 AM
Post #9 of 9
(2585 views)
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Re: Grinding noise
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Glad too and happy 4th. Who knows now but it's found and done - good for you. Why it wobbled isn't your problem now but I think some bearings are held with snap rings that are directional - usually you get away with it depending if so. Well I guess not.
Shows to go you as they say NEW doesn't mean it's out of the question right of the box!
Have a great day,
T
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