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Noisy alternator when cold.

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The alternator makes a whining noise when I start the car when it's cold. It quiets down after running a few minutes. There aren't any charging issues. Are the bearings the issue or is it something else? If need be can these alternators be rebuilt with minimal effort?
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1998 Rav4, manual transmission, 2WD, JDM engine installed in 2013
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A squeal from the alternator belt when the weather is cold is the classic symptom for a loose belt.

The first thing I would do is check the belt tension.

For some help on adjusting the belt tension, start by taking a look at page 7, 10 and 24 of the attachment.
 

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Did you try tightening the belt? They stretch over time. find the middle if the longest section of the belt between 2 points, then with one hand try to twist the belt, if you can easily twist it past 90 degrees it is too loose. Also check the belt before you start it in the morning for any damage, glazed surface, moisture or oils getting on it.
 

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I use this Gates 91132:

I got a couple of those for my Lexus when I did my timing belt change out for the power steering and alternator belts, but they turned out to be useless. Maybe if you have a larger engine with much more distance between the pulleys you can get a more accurate reading with these but I found on my car they would not give a consistent reading, I was very careful, and it would read way below spec, then try again and it would read high, then a third reading would be low again, not even close either. I tried dozens of times to get a consistent or at least close to consistent reading but never could. I ended up defaulting to the mechanics' old proven standard of the twist method. You twist the belt with your fingers in the middle of the longest length when you can no longer twist it past 90 degrees you are good, if it goes past 90 you are too loose if you can't get 90 without too much effort then it is a bit too tight.
 

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Discussion Starter · #6 · (Edited)
No it's definitely not a loose belt. LOL. I've worked on cars for over 40 years and I know what that sounds like. It's a definite whirring sound coming from the alternator. I'm thinking it's possibly the bearings or something else internal.
 

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1993 Camry SE,V6-5MT
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Have you used a hose, or a long rod as a mechanic's stethoscope to confirm which bearing is making the noise?
Or, you can buy an actual mechanic's stethoscope at the auto parts store for the same effect (I find a long rod works quite well for me - hold one end on the part and the other end at my ear).

Listen at the front and at the rear of the alternator, the AC compressor, the PS pump, and also at the water pump and each idler, until you find which bearing is the loud one.
 

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Discussion Starter · #8 ·
No I haven't gone that far to check. I've just poked my head by the alternator and listened to it. I'll check my manuals to see what's involved to service the alternator.
 

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No I haven't gone that far to check. I've just poked my head by the alternator and listened to it. I'll check my manuals to see what's involved to service the alternator.
I just went through similar stuff on my 2012 Camry. See my posts 6-13 here Alternator diagnosis and replacement.
Even though the alternator checked ok, it was running very very hot to touch and I suspect it was the bearing.
 

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Most likely mechanical. As you've ruled out the belt, before taking it apart check that the bolts that hold the shells together are tight - I've had them come loose and cause interesting noises.

Bearings are easily replaced with a few tools, it helps to have access to an arbor press or a good vise.

You might as well throw in new brushes while you're in there and clean up the slip rings if they need it.

Depending on its age, you also could consider new diodes and voltage regulator - these can last the life of the car but after 100kmi. or so they don't owe you anything.
 

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Discussion Starter · #14 ·
As far as I can tell the alternator looks original and the car has over 221K miles. I notice that the headlights dim a very tiny amount when hitting the brakes so there's probably a small output deficiency.
 

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As far as I can tell the alternator looks original and the car has over 221K miles. I notice that the headlights dim a very tiny amount when hitting the brakes so there's probably a small output deficiency.
Given its miles and the fact it's starting to make noise you might want to give it a thorough going over, including insulation resistance testing. Replacing still functioning parts like diodes and regulator is up to you and will depend on considerations like your need for reliability, how long you plan to keep it, etc.

Is the dimming when slowing down a new thing or is there a chance you're just noticing it now? If new it might mean the alternator has become less efficient, but it also might be as simple as poor connections or an aging battery.

An AAA service guy once performed fairly sophisticated testing on our charging system when replacing a failed battery. I understand some parts stores, including Sears, perform this service though I don't know how thorough those are.
 

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Given its miles and the fact it's starting to make noise you might want to give it a thorough going over, including insulation resistance testing. Replacing still functioning parts like diodes and regulator is up to you and will depend on considerations like your need for reliability, how long you plan to keep it, etc.

Is the dimming when slowing down a new thing or is there a chance you're just noticing it now? If new it might mean the alternator has become less efficient, but it also might be as simple as poor connections or an aging battery.

An AAA service guy once performed fairly sophisticated testing on our charging system when replacing a failed battery. I understand some parts stores, including Sears, perform this service though I don't know how thorough those are.
Just replace at that miles do not rebuild. Labor of off and on at that miles get new one so you have piece of mind and new belt
 

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"Just replace at that miles do not rebuild."

This is where a mechanic who does all their own work and who finds it is rewarding to solve problems, may differ from a production mechanic (who works at a shop and who is paid by the repair), or someone who's time is quite limited and just has to get that car back on the road for work Monday morning. It is fast to R&R a questionable part with a new one from a box. But, aftermarket rebuilt parts do tend to come with their own issues (durability, parts quality) that sometimes can cause the work to have to be re-done, or may not last as long as the original part did.

What I found really interesting was just how reasonable the individual component costs were, and how easy it was to test and repair parts like starters and alternators, brake calipers, master cylinders and power steering pumps. Rebuilding an OE Toyota part typically assures you can get the same crazy long life it gave first time around. If you throw that away and drop in an eBay part all bets are off.

But, it is true rebuilding does take more time than simple replacement.
 

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Discussion Starter · #18 ·
I've read my share of stories where the so called rebuilt part is bad out of the box. The only accessory I've R&R'd was an A/C compressor. Fortunately I was able to find a new one at a reasonable price. I'm sure I could rebuild the alternator reasonably. I trust my labor more than a remanufacturing shop that spits out 100's of these a day.
 

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There have been several posts in the past few months about noisy alternators. Perhaps you do have a bad bearing but don't miss Circlotron's comment above regarding a little extra noise during a recharge cycle.
I have also recently noticed noise from my alternator and I did a rebuild including new bearings. It still sometimes makes more noise than one might expect.
 
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