Engine rattle
Thread Starter
Racer
Joined: May 2017
Posts: 256
Likes: 12
From: Everett WA
Engine rattle
I have a rattling noise coming from my 2001 LS1. (130K miles) A mechanic friend and I agreed it seemed to be coming from the alternator. So I pulled the serpentine belt, and spun the alternator by hand, and the bearings seemed smooth. Then I noticed that there was a rocking motion on the pulley relative to the shaft. I immediately thought "Aha! That must be it". So I ordered a new, $200. alternator. But then I've since learned about the 2001 C5 "Clutch pulley", and I wonder if that little bit of play is normal, and my rattling sound originates elsewhere?
Drifting
Joined: Mar 2013
Posts: 1,496
Likes: 353
From: Little Rock Arkansas
One thing I would recommend doing before you install that new alternator you ordered is read the sticky in the Tech section re: alternators.
Many of the current alternators that are sold have the same part numbers as ones that go onto C5s, but the C5 -specific alternators have extra elements in them for the PCM duty cycle. There are a tremendous amount of instances of individuals buying new alternators, sending their old ones off as cores, and subsequently realizing that the alternator they bought is actually not "correct" as it doesn't account for the PCM cycle and usually throws a charging system fault. The icing on the cake then being as their old one was sent off as core there's no easy way to rectify the issue.
I do agree though that you should check everything on the serpentine drive before going and replacing the alternator. Remember you have two idler pulleys (one for main belt and one for A/C belt) that often also rattle or make similar noise.
Many of the current alternators that are sold have the same part numbers as ones that go onto C5s, but the C5 -specific alternators have extra elements in them for the PCM duty cycle. There are a tremendous amount of instances of individuals buying new alternators, sending their old ones off as cores, and subsequently realizing that the alternator they bought is actually not "correct" as it doesn't account for the PCM cycle and usually throws a charging system fault. The icing on the cake then being as their old one was sent off as core there's no easy way to rectify the issue.
I do agree though that you should check everything on the serpentine drive before going and replacing the alternator. Remember you have two idler pulleys (one for main belt and one for A/C belt) that often also rattle or make similar noise.
Thread Starter
Racer
Joined: May 2017
Posts: 256
Likes: 12
From: Everett WA
Thanks guys for the info. I hear, and agree. I'll check all idler pulleys tonight, and I'm glad that I kept my core. I didn't believe it when the "Expert" at Autzone told me the slight relative movement of my pulley meant a bad bearing.. I'm betting that he, like I had never heard of a decoupler pulley.
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