Hi, I have a 2005 base LS2 C6 with 70k miles. Most (75%) of the miles I've put on it are city/local driving, short trips under 5 miles. Bought used so unsure of the history.

6 weeks ago as the weather got colder, I noticed some minor belt squeal. It was generally only at a cold start up and would disappear eventually. I degreased the serpertine belt to see maybe it was just dirt/oil build up causing the squeak. It didn't really help, so I took it to reputable mechanic shop #1 (smaller shop, one mechanic). He replaced the serpentine belt and idler, and mentioned both the harmonic balancer and tensioner had a slight wobble (would be $800 to replace but unsure if that was the cause, belt+idler work seemed to fix it). Within a week the squeal was back (so I'm thinking the mechanic probably used a durable lubricant somewhere, so only seemed fixed). At this point the squealing now was lasted longer and would get louder when accelerating, which was new.

I then took the car to reputable mechanic shop #2 (bigger shop, 3-4 mechanics). These guys replaced the tensioner pulley, confirmed minor harmonic balancer wobble but also like mechanic #1 said, didn't think this was the culprit. Squeal seemed fixed on the drive home. The next day, cold start in my garage and the squeal was back, so I immediately took it back to the shop. Shop was far enough away the engine was warmed and no squeal when I pulled up. They removed the AC belt, and said to wait til next day's cold start to see if this resolved it. Following day, AC belt removal had no effect so brought it back to the shop. Left it overnight for them to diagnose cold start squeal in the AM and put the AC belt back on.

This morning they called: they're not really sure but what it is...for $300 want to re-replace idler and serpertine belt (mech#1's work), and then consider replacing harmonic balance, fuel pump, etc. which could cost in excess of $1500 w/ no guarantees that any of their work will fix it.

I've been researching all threads w/ LS2 squealing, I'm wondering if it could be a bad alternator? Had battery keep dying on me 4-5 months ago, but resolved it after I replaced the original battery. Also noticed some flicker-dimming of rear tail lights/interior dash lights (before and after battery replacement). I'm wondering if this was an indicator of a failing alternator. Then, on a cold start the alternator is working extra hard causing the belt squeal? I'm not a mechanic by any means so I'm really struggling here.

I really appreciate any input.. thanks! It's a beautiful car, and it's unfortunate that it sounds like a 1992 Saturn.

 

Harmonic balancer is my vote. If it's wobbling it needs to be replaced.

 

I agree, probably the balancer.

If you don't know any history on the car I suggest you go to a Chev or GM dealer and ask for a printout of the GMVIS for your car. It will show all warranty work and maintenance / repair work done by any GM dealer.

 

According to what others here have said, a slight side-to-side wobble does NOT necessarily mean the balancer is bad. It may have been like that since new. Disclaimer: This is what others have said, I have no experience with bad C6 HBs.

In 50 years of car ownership, I have never had to replace an HB but the C6 will probably be my first. '07, 30k miles, still okay though.

 

 

Any shop that wants to throw money at a repair to see if it fixes the problem should no be working on a car...at least won't be working on mine. With that said, which of the three tensioners got replaced?

A wobble on the HB does not mean it is the cause of the squealing. To my knowledge there is no bearing on the HB itself. If you remove the serpentine belt and it's still making noise, the belt is not the issue. The HB should still be replaced if the wobble is that bad.

Hope this helps a little.

 

Get away from the mechanic that wants to replace your fuel pump. It's not related to any kind of underhood squeal. Isolate the squeal with a stethoscope or an old heater hose held to you ear and the other end to the suspected part. Must test, not guess for the problem. It's possible the alternators internal bearings are going bad. Inspect the belt for imbedded debris or a small piece of gravel in the grooves of the belt. Beyond that I would suspect the harmonic balancer or the other tensioner or idler pulleys. Water pump and power steering should be considered also. Again it needs to be tested to isolate the problem so unnecessary parts are not thrown at it raising your cost.

 

Does the harmonic balancer wobble more when the car is cold? Might be something to look at/for as you troubleshoot. I am guessing it's wobbling enough to make the cold belt squeal. Good luck and please keep us posted.

 

had a noise on my 07 that i couldn't isolate with a stethoscope. PS pump or alternator. Lucky me the alternator bearing totally failed in the middle of a road trip. Replaced in O'Reilly's parking lot.

Check for alternator noise.

 

Good chance your noise is coming from one of the other pulleys (assuming the balancer wobble is not too bad). I replaced my balancer and still had a little squeak. Pulled all of the pulleys, took them apart, cleaned them and packed with fresh grease. No more noise. Easy to do. Took about an hour to do all pulleys. No need to replace them.

 

I had the exact same problem with my C5 corvette. Finally put what they call a alligator belt on it, and that got rid of the squeal. NAPA should have these.

 

Check the old belt for worn frayed edges, if so this is an indication of misalignment of the pulleys or wobbly HB.
My car developed a cold start up belt chirp that worsen. I replaced the belt and one pulley, but the cold start up chirp returned. Both the old and new belt showed signs of frayed edges. My HB always had a slight wobble, but it seemed to have worsen. I replaced the HB with an ATI HB and no more cold start up chirping.

 

QUOTE=fourth vette;1593949210]I had the exact same problem with my C5 corvette. Finally put what they call a alligator belt on it, and that got rid of the squeal. NAPA should have these.[/QUOTE]


The brand of belt is Gatorback, not Aligator

 

My 2012 that I bought new had a slight squeal at 9k miles. Sure enough as soon as the dealer heard it he said balancer without even looking although he did show me the wobble after he made that statement. Again it also wasn't that much either, but I guess enough to make a squeal.