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Alternator or Idler pulley?

O

over_30k

CEG'er
Joined
Mar 19, 2007
Messages
382
Location
Mississauga, Ontario
Did anyone have their alternator bearings fail? How did it sound, and how did you go about troubleshooting? I think mine are gone. It’s still charging fine and there is no play in the alternator pulley.
I changed the belt and tensioner pulley about 2 months ago. Recently I started hearing a rattle like noise. It goes away when I release the tension on the belt. I bought an idler pulley and about to install it. I'm usually good finding noise using a metal rod to the ear method but can’t quite pinpoint this one.
 
over_30k said:
I'm usually good finding noise using a metal rod to the ear method but can’t quite pinpoint this one.
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:confused::confused::confused: never heard of that method..... seriously... please explain it 2 me...


if you took the belt off the alternator you could spin the pulley by hand and should be able to tell if the bearings are shot or not... or at least i believe you should be able to...

you say it's a rattle that you hear.... is it a constant sound? does it speed up or slow down with engine rpms? does it change any if you're moving or the car is still? any more info you could give about it could help narrow it down...
 
Yank the belt and start spinnin'. Usually you can find the bad one that way. Bad pulley will be noisy, grind, or howl, if a knocking noise don't be surprised if it turns out to be the tensioner just changed. There are some really crappy ones out there, I have seen new ones lock up in as little as 2 weeks before. Some use a really stupid idea of teflon coated tape that goes between the coils of the spring, when that tape works its' way out and loose, it then balls up in a wad to lock up the unit. Wonder what moron thought that one up. Autozone tensioners for what it's worth.
 
Sorry, was busy with things. Yes it's confirmed it's an alternator bearing, one on the regulator side. The whole alternator housing is also cracked up like most I've seen on these cars. I’ve armed myself with long extensions and some flex joints and will be tackling it this weekend. This is my 4th change on these cars so I can do it in about an hour and half, providing I don’t have to fight with bolts and nuts. I was lucky to find a good rebuilder that does superb job. The last two he did are holding up well. One on my 95GL is almost over 100k and works like a champ, the other one on SE is over 50k. He told me that the ones sold in most part stores are almost guaranteed to fail because parts used to rebuild them are not OEM. Sometimes they fail the minute you put load on it. Apparently he uses all OEM parts. Anyway, I don’t care what he uses all I know I had good experience with him.
To answer your question about finding noise using a metal rod; I use long extension, one end to the ear and other touching different parts of the engine till I find it. Works just like the stethoscope, sound travels through it.
 
Mine lasted almost 130K miles then it started to make a sound like dull, low pitched air raid siren - then it stopped charging when the fusable link blew. Idiot light never came on due to the blown link. Got an rebuilt OEM unit because of all the problems I had with AutoZone specials. My brother went through 3 Duramax alternators on one car he had. I had some bad experiences with AZ waterpumps and engine control modules on other cars.
 
2X95SEs said:
Mine lasted almost 130K miles then it started to make a sound like dull, low pitched air raid siren - then it stopped charging when the fusable link blew. Idiot light never came on due to the blown link. Got an rebuilt OEM unit because of all the problems I had with AutoZone specials. My brother went through 3 Duramax alternators on one car he had. I had some bad experiences with AZ waterpumps and engine control modules on other cars.
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I've heard of others having problems with AZ parts... but to be honest... i've NEVER had a problem with them and i've used them to rebuild at least 3 engines.... and these rebuilds were pretty much only using the original block and heads from the previous engines (if possible.. one block was totaaaallllly F'd up....) so i guess it's kinda a gamble....but with some of their parts, and they may look at you funny at first, but with at least alternators and starters they can test them right there, right out of the box... and should they fail the test i'm sure their original funny look might be a different funny look... haha..
 
Does anyone have any video of this sound? I have the same in the one I just bought. I have a new idler on the way and it does makes some noise but I didn't think it was THAT bad....I didn't consider the "back" side of the alternator.
Like many above it charges no problem but one of the pulleys makes a nasty grinding sound. Spinning the alternator by hand sounds find.

Using the stethescope proved out the idler, i'm just still skeptical.
I used to use the screwdriver and extension trick...but it's much easier to use a actual automotive scope when the car is running with those accessories flying around.
 
98CSVT.....I have a rattle that sounds like it is motion related. I removed the belt and still had the noise. Seemes to be coming through the foot area of the floorboard on passenger side. Thought it could be alternator but it's charging OK. Thought perhaps the internal fan was loose???

I changed wheel bearing, thinking this was the issue but still have the rattle.
 
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