Alternator Question.


Well-Known Member
When starting the engine, there is a bearing squeak, it does go away when the temp on the engine reaches the temp line in between 100 and 210. So I took the belt off and the only pulley that makes noise is the alternator. Now here's the question, can I just pull the pulley and replace the bearing or is it a whole new alternator? :confused:


Well-Known Member
Try a new belt first.

Alt bearings may "feel" bad, but it is usually a magnetic bump that you are feeling.

If the noise goes away as the engine warms, that is a classic belt problem.

Remember, the short trucks use the long belt, the long trucks use the short belt (red litmus turns blue, blue litmus turns red)

kickass audio

Well-Known Member
Let me chime in on your issue. I have a 270 amp Mechman Alternator in my Envoy and it has a slight squeak to it when I spin it by hand but that is only at low speeds and I can't get it anywhere near the speed it has with the engine running. What you can try to do is get a spray bottle of water and fill it with JUST WATER, do NOT use anything else! Start the engine when its cold and when it squeaks spray the back (flat) side of the belt. If the squeaking goes away then the problem is with something on the back side of the belt slipping and is usually a tension related problem too. If the squeaking happens to stay then you can try to spray the ribbed side of the belt. If the squeaking goes away then you have an alignment issue with the ribbed side of your belt and you might have it where the power steering, alternator or A/C compressor is out of alignment with the crankshaft pulley. If you don't happen to notice any of the aforementioned cases correct the squeaking you have then you probably have a bad idler pulley which is located right below the alternator. I had to replace mine 2 times, the first time was the OEM pulley with 100k miles on it and it had bad wobble, the second time it was a new (dayco ..!..) replacement that went to crap out of the box. the third was a new dayco replacement that had no issues and is still on my truck after 26k miles.

I had problems with belt chirp on my envoy real bad after a few months of getting a new Advance Auto belt which is a crappy Dayco belt. Those damn things have almost like a lacquer on the back side of the belt that makes the squeal go away because it slides over the pulley's that are problematic. After about 3 months that coating wears off and you get the squeal right back again.

What I would do is this:

1.) double check your pulley's for any play and if you have ones with a lot of play replace them as the bearings on them are worn out. Check that idler pulley the most because that one squeaks when cold, at least it did on my truck and once it was hot it went away.
2.) If everything checks out with that then check your tensioner for play, if it bounces really sloppily when idling then your tensioners bushings are bad and you should get a new tensioner. Another way to confirm this is to look at the back side of the belt, if you can see what looks like bump marks on it then that is a 100% sign your tensioner is shot. I also recommend getting a new belt too if you replace the tensioner.
3.) If you still have the squeal do the water trick I mentioned above. Note: do not soak the death out of the belt. Just give it like 2 squirts of water and stop. You don't want to get water in your alt or sling it all over the engine.
4.) I always when I have belt issues get some brake cleaner and a few paper towels and spray the paper towel and clean out EVERY pulley on the drive system. do NOT spray the cleaner on the pulley's because if it gets off the pulley and gets into the bearings it will eat away at the grease and wear out the bearings.
5.) If your belt is worn, shows bumps on the back side or you replace the tensioner I STRONGLY recommend getting a GATES belt. Thats what I run on my truck and have had it on for over a year without a single chirp other than when my truck shifts from first to second at WOT. This is the exact one I got: CARQUEST - Product Information:CARQUEST Premium Serpentine Belts By Gates its costly but well worth it for how many of those crap advance auto dayco belts I have been through.

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