alternator whine

Buffalo · May 10, 2012

I have a 2002 3.0L Ranger and it started making an intermittent whine. It sounds like it's coming from the alternator. It sounds like when the tensioner pulley was on its way out. Is there a way to test the alternator pulley? Is the pulley on its own bearing and can I replace this part only or will an alternator only come as a complete assembly? There have been no electrical or charging problems, just the noise.

hondaxr650 · May 10, 2012

The pulley is just a chunk of metal. The only bearings are inside the alternator.

Earl43P · May 10, 2012

Just get a new or reman.
Typical alternator lasts about 140k miles.
Brushes or a bearing, in your case, probably the pulley side bearing failed.
Not for the typical DIY'er, although it is possible to replace.

Buffalo · May 18, 2012

Well, it's not the alternator making the noise. Should I put the old one back on because it still has life or keep the new one?

dankhimself · May 18, 2012

Just something that happened to me, I thought the same you did once, and it was just the idler pulley for the belt, its just a standalone pulley that spins on bearings so the belt can be routed around all of the accessories properly. When I went to ford they had a superceeded part and the bearings were totally different in the new one, bigger and the seals seemed different. Listen closely to that, it might he your problem. You can run the old alternator and return the new one, but since you changed it and the other is so old, just leave it unless you need The cash bad. Plus you can clean up the old one in your spare time and rebuild it so you have another Incase something happens in the future. Is there a warranty on the new one?

Buffalo · May 18, 2012

Two year warranty on the new one. Old one looks original, 138k miles on the odometer.

I changed the idler pulley and tensioner last year, but I guess it's possible one of them is dying.

Tractor Dan · May 18, 2012

Could very well be the idler pulley. Only saying that because i saw a friends go within a year or so of him replacing it. I replaced mine when i had to put my second tensioner on. The first replacement went bad within a year so it was under warranty. :headbang:

I done the idler at the same time. Not sure if i have the "correct" pulley on there. It's the same size and everything as what is listed for the 3.0 but instead of being a plastic pulley with a lip on each side it's metal and smooth no lip. Think the autozone guy said after he looked it up and cross referenced it was off a 4.0. Either way we put that samed style on and ever since works great. Except now my tensioner is again going bad. So heck check the pulley, it's worth a shot since you just gotta loosen the belt and then spin the pulley. I was able to spin mine and tell the bearings were going.

dankhimself · May 18, 2012

That is the 4.0 pulley u have, mine is the same, no lip. Now let's get a little more half-ass technical. You say whine. Could it be a buzz? That's a worn loose bearing noise. A consistent squeak? That could be a dry bearing noise, or belt(which I doubt is your problem, more of a squeal noise). A whine is more of a power steering pump normal operation noise, or the noise an alt makes before it goes, but yours is new. I had a good week of noise diagnostics in MMI Orlando, what a funny class that was. I forget a bunch of them now that I think of it, im gonna rip out my books and get some more later today.

Try to isolate the noise I guess, I wish I could hear this thing! You're sure it's on that side of the engine right? Sometimes rattles, like a/c clutch noises when they have loose parts, even the compressors sound like that sometimes when they are running. If I find my noise diag. sheet from school, I bet I would get it posted in the tech section, all my bike tech buddies and I diagnose over the phone all the time when we are stumped and people wonder what the hell we are talking about, but it always works.

Even a cellphone video helps man, put the microphone up to the ac, then the pulley bearing, then the alternator, all that stuff, at a nice low idle before the cooling fan kicks in. Even a set of internet ears can be of help sometimes Haha. Good luck man.

Buffalo · Jun 1, 2012

New developments:

It's a chirping sound, nearly the same as what was happening before I changed my tensioner. Tensioner and idler pulley are both about a year old. I guess it's possible they're failing again. The strange part is that it disappeared for about a day, and now it's back with a vengeance.

Driving on the freeway ~65mph, the noise increased and the battery charging light came on, as well as a drop in charging voltage. I guess because there wasn't enough tension in the belt to keep the alternator rotating at a high enough rpm. Alternator is new, and it didn't change the the noise or the frequency of when it occurs. After I came off the freeway and back to city speeds, the noise quieted down and charging went back up. I'll take the belt off today and check it for wear, and see if there are any obvious signs of failure in the pulleys. I assume all the pulleys should be able to spin by hand?

AllanD · Jun 1, 2012

Accessory belt pulleys and belt tensioners are something you should actually look in the junkyard for.

Why do I say this? because parts prone to failure are parts other people tend to need to replace, and if you keep looking and be observant you'll likey find a junkyard ranger or explorer on which someone else has already (recently) replaced those same parts....

Frankly I have three complete sets of '94-up idlers and tensioners that I gathered
as "junkyard gold" one set is actually in my truck with my spare belt and
the tools to change the belt.

BTW if ever you have the least excuse... on a 1990-93 4.0 you should switch to the 1994-up alternator bracket/idler/tensioner setup, because this eliminates the one left hand thread bolt used in the 1990-93 pullet hub and oddly the 1994-up "Bottom mounted" tensioner is actually MORE accessable than the 1990-93 top mounted tensioner.

the later parts were made from 1994 through the end of 4.0OHV production in '01, seven years, the "earlier" 1990-93 setup was only used for four years, ending eighteen years ago... which parts do you think will be available longer?

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Buffalo · Jun 1, 2012

Here's some video with audio. It's gotten much worse, and it only happens after the engine is warmed up. It's difficult to pinpoint, but it sounds like it might be originating from the back of the engine.

http://www.youtube.com/watch?v=OvFKRsrGLu0

www.youtube.com/watch?v=rAnxo1Tlxh0

Buffalo · Jun 2, 2012

Is it a whole assembly replacement? Do you have a Ford part number? From the picture it doesn't look like the gear is removeable.

alternator whine

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