HELP!! 1997 LeSabre Squealing Squeaking Noise Drives Me Crazy

'97 LeSabre Limited, 190K, developed a weird high pitch squealing/squeaking noise from the belt side about 1 month ago.

When the engine starts cold, everything is fine; but after 15 to 20 min driving(generally very accurate about that time), the noise would come on when the RPM changes, i.e when I release the gas or hit the brake that the RPM drops, or when I hit the gas again to accelerate that the RPM rises, the squealing noise would come on for like 4-5 seconds, then goes away when the RPM gets steady. So generally not that serious at highway driving, but at the stop'n go city driving, it really drives me crazy.(and also the pedestrians, it's REALLY LOUD!!)

I did a lot of work on the belt side in the past month:

New serpentine belt, with belt conditioner spray, WD-40 spray---no use;
then I replaced the idle pully on the belt tensioner, since the bearing of the old one seems to be somehow loose--but no use:uhoh: ;
so I came to the waterpump and thought that might be where the noise is from, get a brand new one on there-- STILL no use:screwy: ;
I was kind of lost so I went to my mechanic for some professional advice, he checked the noised and pointed out that the noise came from the alternator/tensioner assembly area.
Following his suggestion, I first chose to replace the whole automatic belt tensioner assembly with a brand new one--sadly, still not it:frown: ;
Finally, I came to the alternator, since the OEM Remys are too pricy, I got a used one with about 50K miles off EBAY and put it on --
THE NOISE IS STILL THERE AND NOW I AM TOTALLY CRAZY :banghead:

Since the A/C compressor is replaced about 6 month ago, the only thing that hasn't been replaced on the belt side is the power steering pump, which I also took out and checked when doing the waterpump job. Since my steering is absolutely fine, i don't think that's the problem either.

So WHERE THE HELL DOES THE NOISE COME FROM???
I'm totally beaten and please help me guys!!!!

thanks in advance

Welcome to the forums, jamesxixi.
Have you considered the possibility of one of your radiator fans causing the squealing? Also, will this sound ever come out at idle, or just while driving as you mentioned?

It certainly sounds like you have an unusual load on some belt driven component. Do you get the noise with the AC off? Is the serpentine belt the right length? You should never need to use WD-40 on a new belt!:nono:
If your drive pulley has any “WD-40” or belt dressing on it, remove the belt and clean the pulley with brake cleaner. All pulleys & belt, should be clean and dry!

After the noise starts yank the belt off and see if the noise is still there. As long as you don't drive the car or run it for an extended period of time you should be ok as far a heat is concerned.This would tell you if it is on the belt drive items. You don't want to try moving the car without the ps activated.

First, greatly appreciate all your advices, guys

here are some updates about the issue:

I drove to my mechanic again this afternoon and did some more diagnosis;

With the engine hot, but shift at Parking, changing the throttle position(i.e the RPM) won't make the noise, so it's definitely has something with the load change to do; (but not the AC, 'cause I got it no matter the AC on or off)

With the engine hot, the noise would also come out when I start or shut off the engine:
when I start it, there would be 3-4 secs, then the noise comes out and lasts about 4-5 secs and then goes away;
when I shut it off, HERE COMES THE WEIRD THING: we notice a very short squealing would come out AFTER THE ENGINE SEIZED FOR 2-3 SECS. So we could say it's definitely not the belt, since when the engine is off, the crankshaft seizes IMMEDIATELY, so the belt and all the belt pullys seize IMMEDIATELY, but the noise come out 2-3 secs AFTER THAT???!!!

And also my mechanic said this time he is sure that the noise comes out from the back of the engine(close to firewall), probably down from the alternator area.

because we're pretty sure that's a high pitch slippering/abrasion noise comes from some spinning device,( or???)

NOW THIS COMES TO A EASIER QUESTION:

WHAT THING THAT SPINS WOULD KEEP SPINING 2-3 SEC AFTER THE ENGINE SEIZES THEN STOPS, AND PROBABLY LOCATED BACK AND DOWN THE ENGINE?

As far as my knowlege goes, I couldn't figure one thing out, especially from the back and down engine area.

So I just made an appointment with my mechanic and let him put the car on the rack sometime to check the origin of the noise

Anyway, I would keep this updated when I got something

Thanks again!!!

This may sound strange but you may have vacuum leak which sometimes is mistaken for a squeal (just a thought).The vacuum may be bleeding off after the engine stops.Good Luck

Check the o-rings on your MAP sensor and PCV. They're located on the front of the composite upper intake manifold. The PCV is underneath the MAP sensor. My '96 LeSabre had the same exact symptoms. I found the solution on another forum by searching for a "whistling" noise instead of a squeal. My problem started when I replaced my upper manifold with an improve part, to avoid the common blown intake gasket problem with the Series II 3800, while changing out a broken composite coolant elbow that was leaking. I didn't realize the PCV was inside the manifold so I didn't transfer it (or the o-ring) to the new piece. Thanks for all your details, you saved me $$$, as I was ready to replace the tensioner assembly and the power steering pump (the seal is leaking anyway) until I tested with the belt off - and no change in the noise. Mine purrs like a kitten now (99,600 mi.) - Phil

Fm James
WHAT THING THAT SPINS WOULD KEEP SPINING 2-3 SEC AFTER THE ENGINE SEIZES THEN STOPS,
AND PROBABLY LOCATED BACK AND DOWN THE ENGINE? From my experience, it would be a fan, which takes a couple of seconds to come to a full stop, after the power source was shut down.