Screeching sound coming from engine

[yizit]

Hello everyone....well it seems when it rains, it pours. Lately we have had a few issues with the RT, and the latest is a screeching sound coming from the engine. It doesn't happen all the time, so the shop is having a hard time tracking it down. They seem to think that it is coming from the AC compressor or related to it. They have not heard this screeching sound that we have heard, but the AC when they test it, makes a short high pitched chirping sound. Nothing like what we hear. It'll make a screeching sound for several blocks and then disappears. We recorded the sound and had them listen to it, but without them actually hearing it, they aren't able to pin point it. Has anyone had this problem? They are suggesting to replace the AC ($900), but we aren't quick to have that done, until they can convince us that's what it is...that's them actually hearing this screeching sound. The first thought was possible belt bearings (??), but again, they have not actually heard it, so they can't confirm it.

 

[markopolo-ClassB]

I've heard unearthly screams caused by worn belts but I'm sure they've ruled that out.

Can you get a second opinion?

 

[yizit]

They said that without being able to "hear" the noise they can't say it is a belt. They think it is the AC, but the noise "they produce" is not the same kind of noise. Their "produced" noise is more of a high pitched chirp to us. The screeching we hear last for several seconds to a minute or two, then it goes away after starting the engine. I can't say that it makes the noise while in idle, because I'll put it in drive and step on the gas, that's when the noise starts.

 

[g1g]

Without hearing it this is sure difficult to say with any accuracy but the only thing that comes to mind is a belt. I would check it out if good tighten it, if bad change it as you should do it anyway. Does it make the noise when the AC is off? If it stops then it would be either the belt or Ac pump. If it still has the noise with it off it is something else.

 

[Johnny R]

It sure sounds like a belt. Especially when it lasts only for a few blocks. Most likely when you pull away from a stop? Next time it does it, quickly turn the heater fan up to full blast, or turn the air conditioning on and off. (to change the electrical load on the alternator.) If the squealing stops, or changes pitch, you have confirmation that it's a belt. It either needs to be either replaced or tightened.
PS: Based on what you write, I can hardly believe that the shop hasn't ruled it out. Go someplace else.

 

[yizit]

I went on YouTube and searched for screeching engine noise. Came across one that when I played it, we both yelled “that’s it”. The guy was a mechanic doing a diagnoses and repair....it was coming from the alternator belt. If our mechanic can’t find it, we are going to suggest replacing the belts first. As far as we know, they are original and we have 74K miles on it. It’s a start I guess. If it is the AC, we’ll find out. Process of elimination. We are planning another trip and would rather the AC stop working, then the engine failing us while on the trip.

 

[Mike-ClassB]

Probably the serpentine belt, if it's the same engine layout, size, equipment, as the 2002 G3500 van.
5.7L V8. I had my GM dealer change mine last year when I had the manifold gasket work done, as it had been suggested by more than one shop/place out on the road, although none of them were GM dealerships. I've been to only 2 GM dealerships with that van, and neither recomended changing the belt. I asked my dealership to do it, since they had the front/top of the engine apart anyway.
They lose their flexibility over time and start to slip eventually when cold, but after a bit of spinning, will warm, flex, and start to grab. It could just be a tensioner pulley has slipped a bit and loosened, and needs to be tightened.
You could check and see how far you can push the longest loose section of belt off it's line of travel. If there's more than an inch or so of travel, it might just need to be tightened up.
The only other squealing noise I hear is when I turn the steering wheel lock to lock (all the way left or
right?) at low (idle) speed, but that wouldn't fit your symptoms, as you're in motion already on the roadway. I think it's power steering assembly related and is usually considered normal. In a big vehicle, anyway.

 

[yizit]

Today we had them replace the 2 belts. For 2 secs they said they heard a noise, but couldn't be sure where it was coming from, but still suspect it's coming from the AC compressor. :thumbdown: We'll be listening for our screeching sound, and if we hear it again, looks like we'll be replacing the compressor. grrrrr

 

[Mike-ClassB]

I think markopolo suggested a second opinion. Have you taken it to a GM/Chev dealership and asked them?
Those guys generally will tell you the straight story. Unless you've had problems with your local GM guys before? Might be cheaper than replacing the AC compressor unnecessarily. One other thought might be the water pump bearings have worn. Can you see any coolant leaks/stains under the water pump, below the pump hub/pulley? Hope your engine stays quiet , ssshhhhhhhhhhhhh :shh: :thumbup:

 

[yizit]

Thanks everyone for your help. We have all our service work done at the local GM dealer shop. They are the ones who said they thought it was coming from the AC compressor. "Thought" is the operative word here, since they have not actually heard the same noise we have. They tried to create the same sound by spraying water in to the AC, but we heard a chirping sound, not the loud screeching noise we normally hear. They said that if they could get it to last longer, they think we would hear that noise, but we haven't and therefore, not ready to spend $900 on a new AC. Time will tell now with the new belts. I'm keeping my fingers crossed that it was the belt. They did say the serpentine belt was worn. According to them they think the AC is going and we may have to replace it in the future. If that is the case, we can at least start saving for a new one. Won't need it now with winter on the way :thumbdown:

 

[leslane]

I have read all the posts about the phantom noise and have had that happen on other vehicles that I own and its always the A/C compressor clutch slipping. It needs to be replaced and it can be done on most models without evacuating the freon, just remove and replace. Not all that expensive either. Hope this helps.
Les
The Yosemite Express builder

 

[Mike-ClassB]

Thanks everyone for your help. We have all our service work done at the local GM dealer shop. They are the ones who said they thought it was coming from the AC compressor. "Thought" is the operative word here, since they have not actually heard the same noise we have. They tried to create the same sound by spraying water in to the AC, but we heard a chirping sound, not the loud screeching noise we normally hear. They said that if they could get it to last longer, they think we would hear that noise, but we haven't and therefore, not ready to spend $900 on a new AC. Time will tell now with the new belts. I'm keeping my fingers crossed that it was the belt. They did say the serpentine belt was worn. According to them they think the AC is going and we may have to replace it in the future. If that is the case, we can at least start saving for a new one. Won't need it now with winter on the way :thumbdown:

This thread is certainly interesting. I hope you can keep us posted on what happens, or what it turns out to be.
Some of us may be facing similar problems sooner than later.

 

[yizit]

I'll be sure to post anything new. I'm hoping it's not the AC. Thanks Les for your input, if our phantom noise reappears we'll be replacing the AC for sure.

 

[leslane]

If its just the clutch on the compressor, you don't have to replace the compressor, just the clutch. As a rule, an automotive a/c compressor will outlive 2 clutches. As the clutch cycles on and off and always under load, it tends to wear out as it is bound to slip a little each time it energizes, thus wearing out the clutch surface. Just my 2 cents.
Les

 

[yizit]

Thanks Les for your input. After we had the belts replaced, we heard our screeching sound again for a very short time. :x So back to the shop. They still haven't heard the sound, but still think that it is coming from the AC compressor, because it is not functioning correctly. Auto mechanic's we are not. Based on their recommendations, we have made the decision to have the AC replaced, since we'll be heading for FL in January. I just hope that cures the problem. It's frustrating to us and the shop. No one wants to replace something that doesn't need to be, and they are not pushing us to replace it. It would be better if the "problem" would just break. Just not when we are traveling rayer:

 

[yizit]

Here's the latest.....we had belts replaced last week and we still heard the screeching for a brief few seconds and took it back to the shop. They still didn't hear the "noise" but still felt it was the AC compressor, so we had that replaced today. While the tech was rechecking everything, he felt one pulley was not working as it should and replaced it. We are leaving for 2 week, 1200 mile trip, on Wednesday. Keep the fingers crossed that the problem was fixed.

 

[leslane]

Sounds to me like you have covered all the bases and hopefully you will have a safe and troublefree trip.
Enjoy!
Les

 

[Mike-ClassB]

So, they replaced a faulty pulley (probably a tensioner, as I mentioned farther back in this thread), as well as the A/C compressor? Seems odd that they didn't notice a bad pulley, when they replaced the main serpentine (or whatever kind
of) belt earlier. If it were me, I'd ask them why that happened, why they found the faulty pulley after they replaced the
A/C compressor. They have to admit both issues could have caused the squealing noise, and one is a lot more expensive
than the other.

 

[yizit]

I thought the same thing Mike. I even ask them about the pulleys when they replaced the belts. They indicated they seemed to be okay. They also said from the beginning that the AC was not operating properly, and would eventually need to be replaced. We considered waiting for the AC to actually die, but with our trip in January to FL, we decided not to wait. We'll never know what, when and how. I just hope we fixed the screeching

 

[Mike-ClassB]

Yeah, I probably would have replaced the A/C parts too, if they looked worn, but I'd sure ask about the "timing" issue.
Have a good trip, and keep "cool"..... 8)