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

Thanks for the info. I'm going to start with a spray bottle full of water!

PS - never noticed directional arrows on my gates belts. Hmmm.

Looks like you found the answer.
I'll bet (1 degree off or not) you can visually see the misalignment.
In any case, hope this is the cure!

I don't think it's misalignment. I think it's slippage. Hopefully, the water test will tell!

Another interesting video from Dayco. There's a part around 2:20 about "Tension decay, from belt relaxation or actual stretch."



I think I have a larger smooth pulley in the garage. Maybe swapping it on will increase tension, and make the noise go away. Will do some tests tomorrow.

Yesterday I found a slightly larger than stock tensioner pulley and installed on the accessory belt drive. This tightened the tension, and should have fixed the squeal if the belt were slipping. Unfortunately, the sound didn't go away - it got significantly louder and more constant (from chirp to squeal). I could still do the water test, but the result of the idler swap test eliminates the SC belt side, and is telling me to focus back on the AC compressor.

The more I think about it, the more this makes sense, based on this quote from Eldo in the AC compressor write-up thread:

[quote'"Eldo"]What you are describing is a classic idler bearing problem. When the pump is stationary and the pulley/hub is freewheeling, you're hearing the worn-out bearing in the hub. When you engage the clutch, the hub and compressor shaft turn as one, so the idler bearing is no longer turning and no longer making noise.[/quote]

The thing I don't understand is, the noise doesn't change very much when I turn the AC on/off - it's a slight change. Considering there's an idler bearing and a shaft bearing, I don't get it. All I know is, there is noise coming from the AC compressor, and it doesn't appear to be the belt.

There's a local parts yard with a used AC Delco compressor for $75. Think I'm headed there soon.

Aaron,
We have a number of NIASE mechanics at the hotel. I'll have them look at it and give their opinion. Hope to see you later. I've got your ride in the GN all lined up

Larry, I really appreciate it. Talk with you later.

If you're not yet confident enough of the source of the problem to take down your AC system, consider the temp swap-out I mentioned with the used compressor..

I'm considering it for sure. Need to find out how much room there is to work with.

The curious side of me wants to see how easy it is to pull off the clutch assembly from the used compressor as practice. If it goes well, I could swap it over to my existing compressor on the car and hope for the best.

AA, Did you solve the mystery squeal?

Almost there, tackling this in my spare time. I removed the compressor clutch from a used compressor found at a local yard. Pressing in a new idler bearing tonight. Then will assemble the fresh clutch assembly to the my original compressor (on the car) and hope for the best.

If that doesn't work, it means the internal AC bearing is the problem. In that case, I'll be reassembling the clutch back to the used compressor and replacing the entire unit.

It turns out pulling the clutch/pulley assembly off the compressor is a piece of cake job. Took me about 20 mins with a couple of puller tools.

Okay, issue solved. Chirp is gone. Problem: user error (me). Solution: under my nose the whole time. Just as the Gates and Dayco videos above both say, it's either slip or misalignment. I ruled out slip, but didn't rule out misalignment.

----> The AC compressor became slightly loose, causing the AC idler pulley to misalign with the belt, creating the chirp. How it loosened I'm not sure. There are 3 nuts securing the compressor to the bracket, and all 3 were spooling off the studs. The compressor was one of the last things I installed when dropping the engine back in, so I'll just accept that they weren't tightened down good enough. Live and learn.

My mistake: assuming the misaligned pulley had to be due to idler bearing. I overlooked the fact that the entire compressor assembly might be misaligned. This was difficult to notice with the accessory belt on, under tension. The nuts didn't appear loose, because the tension pulled the compressor tight up against them. It wasn't until I removed the belt and tried wiggling the AC idler pulley that I noticed the entire compressor bobbling on the bracket. Ugh. At least this didn't cost a lot to fix.

Will reassemble the used AC compressor and try returning it to the yard. Since I did remove the AC clutch and idler pulley, I took some pics and will post a write-up soon.

Great news! Sounds easy to have overlooked. You were always on the right track, so eventually you found the little bastard Eureka

I'm getting a belt squeak from my 97. It's not too loud normally, but it always seems there at cold idle, worse then it's really cold or wet. I just changed both belts, they are new, as well as every single idler pulley. I think it's coming from my P/S pump, you can see the pulley wobble slightly, and it honestly never really sounded that great since I owned the car. Advice/tips?

Thanks
Matt

Try the water spray bottle diagnosis: spray water on belt. This will identify which belt. If chirp goes away, it's a pulley alignment issue (wobbly pulley). If noise gets louder, it's the belt slipping (bad belt or pulley not spinning).

Scroll down for videos: https://rivperformance.editboard.com/t5509p120-faq-chirp-chirp-chirp-belt-squeal-pulley-tensioner-squeak

Where's the thread/image comparing the ribs on the zzp and intense pulleys? I know I've seen it before!

Well here is what just happened. I start the riv today and sprayed water on the belts at idle. Not at chirp or squeak. but then while driving to work it started to constantly squeak with rpm and throttle. Gah. I'm here at work now and while sitting idle if I bring up the RPM's, it really starts to squeak. at idle there is nothing.

Is there any fluid leaking? Any coolant smell?

No major leaks, no. the coolant elbows are new as well.

Get a piece of hose you can hold to your ear and use it like a stethoscope. Find the source. Could be the alternator, A/C pump, idler pulley, any of the above...

I just drove home from work, and it was constantly slipping the whole way home. I admit it was misting outside and very humid, but it was bad. Not as bad at idle, but at like 1500RPM, even without any load it's like a really fast CHIRP CHIRP CHIRP...etc. Going from sound, it is definitely the accessory belt, and definitely from the P/S and water pump area. After I shut the engine off, I did feel wetness under the return coolant "elbow", but I'm not certain it was coolant as alot of things were wet because of the weather, however, there did seem to be a wide "line" of wetness on the firewall in-line with that belt, so I don't know.

Make sure that the water pump isn't leaking from the weep hole. That will sling coolant onto the firewall and mist that whole area.

This is why I was asking about the coolant smell. Your situation seems to be a slipping belt, which can result from a leak as Larry pointed out. Also the water pump pulley can become wobbly as it gets worse, creating a combo of chirp and squeal that's difficult to diagnose.

I had this issue about a year ago - not saying yours is the same, but the symptoms are similar. Here's a link to the write-up. Scroll down for my video post of the wobbly water pump pulley:

https://rivperformance.editboard.com/t8340-write-up-water-pump-series-ii-sc

Take the belt off the tensioner and spin and wiggle all your idler pulleys, accessories and pumps by hand.

well from what I can tell, looks like my water pump is spraying a fine mist on my belt, just a guess from the fact that the back of the belt is.."bubbling up" from all the slip, and I see small deposits on the W/P pulley.

Pretty sure the W/P is original and has 147K on it.

EDIT: Also, today after I ran the engine for a few mintues, it was REALLY hard to start after that, so I think coolant was getting on the Cam sensor as well...

The way to know is to slip off the belt and wiggle the pulley with your hand. If it's loose, needs changed

Also, your coolant level will drop if driven far in this condition. If left unchecked, engine coolant temp will rise. Keep a close watch on this.

The moisture may or may not be causing the starting issue. Could be completely unrelated.