I have had a high pitched squealing coming from my engine since I did my h/c a few years ago. After we ran it on the dyno immediately after doing the engine work this intermittent squeal started. I had a mechanic look at it and he said it sounded like it was coming from the clutch. So I had the clutch, flywheel, and slave swapped out, and the squeal came back. It wasn't a total loss as I wanted to upgrade the clutch anyway. After the clutch never remedied this terrible noise I started changing pulleys and belts. I changed the main tensioner, the engine idler, the a/c tensioner and the serpentine belt, and it is still there so by the power of deduction I concluded that it had to be the compressor bearing. I worked international for a few years and had the car in storage so I finally got around to changing the compressor out last weekend. I thought I had it, and then it started again. I have since swapped out both of the a/c belt pullies and the a/c belt and it is still there.

To better describe the sound, it sounds like a squealing belt but it is not consistent. It is very intermittent and irregular when it starts to squeal. It will not do it when the car is cold but I have left the car idling in my garage for over an hour and it will not make the noise but then I can drive it for a mile and it will start and then it will continue while idling. Last week after changing the compressor I drove it to work and it never started making the noise for the entire trip (about a half an hour drive) so I thought the compressor swap had it cured but as I pulled Into the parking lot at my job it started again. Once it starts it will stay squealing but like I mentioned it is very irregular and intermittent when it starts. It is high pitched and definitely sounds like it is coming from a rotating part but the only thing I have not changed is the water pump. When I shut the car off, the engine stops and the sound continues and then dies out kind of like a tuning fork.

I am at a total loss as to what it can be at this point.

I really hope there is a corvette guru out there that can help me because this is really driving me nuts now.

 

Check the routing and condition of all of your vacuum lines including the PCV system.
Make sure the small vacuum line on the rear of the intake is hooked up, it's a real bear to get to.

 

Loosen the oil cap and listen for a swoosh of air come out and the squeel go away. That will be the indicator that it is the PCV system,

 

Not sure of the exact sound, but I have had high pitched sounds three times on my C5, they include the PS pump, belt tensioner, and alternator.

I agree with above, check your vacuum lines first. If they clear, check your PS pump and alternator with a mechanic stethoscope. You can get one for about $15. Good luck with finding it, and let us know what it was. Always up for finding out about other causes of those pesky noises.

Mike C

 

The sound continues after you stop the engine and you're replacing all kinds of parts that only move while it's running??? Did I miss something here? Vacuum would continue to leak after the engine stops, so that suggestion is a possibility.

 

I had a squealing noise like that once, sounds like a belt.....I kept looking in the engine comparment, but nothing.....

Then I realized it was fan assembly that blows air into the car.....it was annoying.....makes your car sound like a klunker.......it sounds like its from the engine because its attached to the firewall or close by.

 

Vacuum leak.

 

What about the radiator fans or the air pump,Blower fan under dash.

 

does it idle smoothly? does your HVAC go from defrost to center to floor?

 

So.....I took the car for drive today until the squealing started and pulled it into the garage, opened the hood and took the oil filler cap out and................................the squealing stopped!

I ordered all of the necessary components to relieve the vacuum on the engine and stop the squealing for good.

Thanks everybody for your help!

 

If that stopped it, you might want to inspect the pcv valve and connection tube to the intake.

 

YOU GOTTA BE SH!TTIN' ME!! All that work for a Vacuum Issue. Man, am I glad I peruse this forum.......I was thinking Harmonic Balancer and it was a freakin' vacuum issue. Just Wow.

Happy that it is resolved for you!