FAQ: Chirp Chirp Chirp - Belt Squeal, Pulley & Tensioner Squeak

After reinstalling my engine about 2 weeks ago, everything was fine except for a random chirp, chirp, chirp when idling that sounded almost exactly like when my tensioner needed replaced. The difference now is, when I hit the gas, the chirp turns into a constant squeal that sounds like the belt is slipping. That never happened when the tensioner was loose. It started out randomly, now it's more constant - problem is getting worse.

Using a stethoscope, I've narrowed it down to the AC compressor for sure. Applying tension to the belt while running doesn't seem to cure the noise. I'm thinking a clutch replacement is in order. Has anyone had their AC clutch become noisy like this? Looking at parts now, there is the assembly, the clutch plate itself, and then there is the clutch pulley, and also the pulley bearing is sold separately. Trying to decide if I should get an entire clutch assembly, or just the bearing? Thoughts on which part might be making the noise?

Mine is doing the same thing Aaron. I haven't looked into it very far, but mine simply squeals and it may only be once or twice a week. My SSEi did the same thing too once in a while. I wish I could help but I just haven't researched it further yet.

Well, mine is more consistent. It happens every day. I did an experiment today - put some drops of oil between the AC pump pulley and the AC idler, let it soak to see if that would quite things down. It did the opposite - got much worse. Sounded a lot like the belt was just slipping, so the oil probably slung onto the belt. After 20 mins of driving, the noise got quieter, and by the time I got home, it was totally quiet at idle.

So now I'm suspecting the belt. I inspected them when I had the engine out, and they both looked very good. Is there a way to clean the belts on the car? I see belt dressing at the auto parts store, but never tried it.

Also, just thinking here - the noise seems to be louder under load, supporting the idea the belt is slipping. If it were the AC compressor pulley bearing, wouldn't that be more constant? I mean, it gets quiet sometimes, sometimes it chirps, and other times it squeals (under load). Can a pulley bearing act like that?

I would suspect the compressor, first, belt last. The way yours is acting is the way my SSEi was acting and I changed the belts on it at one point with no change .

I would not have used oil. An old mechanic's trick is to hold a bar of soap against the side of a V belt as the engine is running. That would quiet a glazed belt. V belts can make a clicking noise that you would swear was a bearing, but it's the belt. Never tried this with a serpentine, but I'd be careful.

The belts are not even 50k miles old, no cracks and not visibly glazed. I want it to be that simple, but I really don't think a new belt is the answer.

I took the car to AutoZone. The guy had a look and said, "It's the idler." I just happened to have a ratchet and a spare pulley in the trunk. Swapped it out and the squeal was still there. He was even more puzzled, then really had no more advice to give.

Today I took it to a local mechanic shop - the manager is a former dealership mechanic. He really seemed to know his stuff, and I trusted this guy immediately. He asked me to start the car with the AC on, then with AC off. Not noticing much difference in the sound, he ruled the AC compressor out. His thinking was, the AC has a pump bearing and an idler pulley bearing. When you turn the AC on/off, the squeal should change as the load changes from one pulley to the other - unless BOTH pulleys happened to fail at the same time, which he felt was unlikely. He also made a comment that most aftermarket "new" AC compressors are refurbished in Mexico, and don't last nearly as long as the OEM. He was thinking we should keep the old one if at all possible.

I asked if he suspected the belts. He said they looked to be in great shape, so unlikely. He then shifted attention to the SAME idler as the AutoZone guy, and after I told him the story, he goes in his shop and comes back with a pulley, throws it on, AND... no dice. Still squeaks. I have him the "I told you so look", which he accepted with a grin. He then listened to all of my pulleys and components with a long screwdriver with no idea which was causing the issue. He suggested I listen carefully to the blower, which I plan to do after work. I know the sound was coming from the AC, but I hope the blower is somehow the problem, as I have another fresh snout sitting at home!

Stay tuned...

Wouldn't it be easier to remove the belt from the compressor to eliminate it?

Please elaborate. What exactly do you mean by removing the belt from the compressor? How would I do this, and what would I expect to gain?

Could you remove the belt from the supercharger to rule that option out?

I expect you would know better than I. That's why I asked.

Answer: the engine won't operate with out that pulley.

Do you have a stethoscope (not a screwdriver)? Sound travels, of course, but you should be able to narrow it down.

98riv wrote:

Could you remove the belt from the supercharger to rule that option out?

I did remove the supercharger belt - one of the first things I tried. Still had the chirp, so it has to be on the accessory side.

The blower pulley was just the mechanic's, and wishful thinking by me that it would magically be it. I am almost certain it's not the blower.

denim wrote:

Answer: the engine won't operate with out that pulley.

Correct, that's why I was asking for more info. The way I understand it, I would need an AC pulley delete, or buy a smaller belt (of unknown size). Both of these options would require added cost and time. If possible I just want to locate the problem and fix, without making things overcomplicated.

Quote :

Do you have a stethoscope (not a screwdriver)? Sound travels, of course, but you should be able to narrow it down.

Yes, as mentioned I used a mechanic's stethoscope. There is no doubt in my mind that it's coming from the compressor pulley, but what I can't be sure about is whether it's the compressor bearings, or if the belt is just slipping in that area.

I have another idea: could be the accessory tensioner isn't quite as strong as it used to be. Without going through the trouble of replacing the tensioner itself, I could replace one of the idler or tensioner pulleys with a slightly larger diameter. That should put more tension on the belt.

It's already past over-complicated.
I'd stick with the stethoscope (if accessible) or screwdriver. Focus on the sound, narrow it down, like Helen Keller. May take some time to acclimate, but the sounds must differ.
Your hunch seems the best one. Maybe a pump that rotates but otherwise is junk. You're friendly pik 'n pull might lend it as a regular customer. Is that easier than a pulley delete?

Really? I like to think of complicated as when I start pulling off parts and spending money. So far all I've done is listen around the bay, temporarily detach the SC belt (5 mins), and let two professionals give their free opinions in exchange for 1/2 hour of my time.

Maybe I should rephrase: I don't want to raise the car, buy any parts, or alter the car's function unless I actually know what's wrong, or at least be fairly certain.

The stethoscope is great for locating the sound, but it's up to me to decide what the sound is. I've pinpointed the sound coming from the AC compressor pulley, however I'm not sure whether it's the belt slipping there, or the AC comp bearing. The sound is near exactly like when my SC idler needed replaced, however a pro mechanic says it's mechanical, not the belt. The Autozone guy thought it was an idler. But LARRY70GS says belts can sound mechanical, and I have to respect that (he's got years of troubleshooting on me). My gut says it's the belt, or a loose tensioner.

The problem with swapping in a used pump: all the freon must be evacuated, then install (see Mr.Riviera's write-up), then the system recharged. And with yard parts, there's no guarantee how long they'll last. If I were going to go through all of that, I'd want a new Delco pump ($$$).

The problem with a pulley delete, the delete kit costs money, and I'd need to evacuate the freon and remove the pump to install it. I don't want to go through that and find out it was my tensioner, you know?

Now, after writing all that, it does feel a bit more complicated, LOL!

(Thanks for all the suggestions, guys. I'll figure it out eventually. If it's the compressor bearing, it won't last very long!)

Addendum: I was suggesting you use a pump that turns only to temporarily replace. Remove the current pump and set it aside somehow, if that's possible.
Anyway, good luck.

So you are suggesting I evacuate the freon, then obtain a non-working AC pump, then remove my current AC pump and substitute, to see if the noise goes away. If it does cure the noise, then I get to do the whole job again to install the new pump. Ok, got it.

AA wrote:

If I were going to go through all of that, I'd want a new Delco pump ($$$).

I can see going that route, but before I get out the tools, what are some opinions on this idea:

I mentioned my problem to a coworker (who is a shade tree mechanic, and also an RIT grad/Engineer). He became preoccupied with the fact that this started happening a short time after I reinstalled the engine. It actually was silent for the first 20 miles, then I heard a light screech, then over the next 500 miles it progressed, and now has find of flattened out, coming back randomly.

His first question: was the serpentine belt replaced in the same exact direction that it was removed? And honestly, I can't remember for sure. I saw where he was going. If the belt were on for 50k miles moving in one direction, and then I turned it around and all the load is pulling it from the opposite direction, could the belt become stretched out slightly? In theory, that makes a lot of sense to me. It's possible the belt's internal cords developed a kind of memory. Anyone else think this is possible?

NO. I'm suggesting you keep the system intact and secure the compressor off to the side, if possible.
Then substitute a workable part to effectively eliminate the suspect part, essentially a pulley delete.
Can't see how you don't understand other than it must be obviously impossible from your perspective.
It's a suggestion, good or bad is your read.

Ok, I didn't understand the part about having two AC compressors attached to my engine at the same time. My apologies. I just never considered that. That's why I was asking that you elaborate, how would I do this, etc. Thanks, I appreciate the suggestion and clarification.

NP. I was thinking you might have a parts guy you use regularly who might lend you a spent compressor as a favor. It's all iffy, but might be easier and cheaper than the delete kit. You may get a whacky sound from the replacement, but it may also eliminate the current bug.
Just a thought. Good Luck.

My main parts guy is Ed Morad. My "local" parts source is AutoZone, lol. Honestly, I don't run into these kinds of problems very often.

What do you think about the belt stretch theory?

Hmmm, it's a theory, but I don't recall ever hearing of belt rotation as an issue before. Still, if it's an easier path and you buy it, it may be worth the effort. Have you researched this theory?
If it's not too humbling and you have a pic 'n pull around, they may still lend you what is essentially a piece of scrap to them, to secure a future customer.
Any way it goes, it's one of those annoying issues you will either throw money or time at to resolve.

Okay, I found this from Gates. Had to laugh when I read the first comment was posted by a SC 3800 owner!



Water bottle sprat test = easy, fast, free. I'd never heard of this before.

Before I snooze:
Belts apparently do need to go back in the same rotation, usually marked with a directional arrow.
Can't say that is your issue, but possible. Apparently older belts can disintegrate if backwards. Yours are newer.
That said, I also read something about a cam sensor that can sound very much like a belt issue.
This was a Ford product issue, so I just toss that out for thought and to add to the hysteria
I think you know what to do.