I am having a problem trying to locate an annoying sound. It sounds like I have an Owl underneath my hood. Just a wooooo that changes with the engine rpm. It does it mostly when I have been driving a while. If i hit the throttle hard it will stop and then will start again.If i try to park the car and raise the hood,the noise mysteriously stops.
The car runs fine and I don't have any codes. Not sure what I should check,any suggestions. Would the tensioner pulley make this sort of noise?
I have replaced the alternator,starter and the tps in the past month.

 

I would check all the pulleys for bad bearings. Could also be a large vacuum leak but youd have drivability issues with a leak that large.

 

im on a phone so cant see any signature at bottom. Some afternarket throttle bodies whistle. I would look for any flatspotting on pulleys especially the tentioner.


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The throttle body is stock,so that rules that out. Ill check the tensioner and see if there are any flat spots or if the pulley is moving freely.

 

If the noise disappears when you open the hood, it may be due to air moving through the radiator, air bypassing the radiator shroud, or some other part of the chassis.

 

Hey guys,
I could never get the noise to stick around long enough to get to my mechanic for him to listen,until today.
He said it was the AIR/Smog pump making the noise. Guess I'll be replacing it in a day or two, or since he is going to track down an oil leak next week for me,I may just let him do it then.
Just though I would let you know in case anybody else has that annoying sound.

 

Ahhhh. I believe the smog pump cycles once at startup. Hence elusive lol. Good find!

 

I'm glad I finally know what it is. That noise was really annoying,and times it was so loud it sounded like I had a turbo under the hood.LOL
He said the bearings were shot and when they got hot,that's when the noise started.

 

AIR pump runs at constant speed for 2 to 3 minutes at startup. Does not vary with engine RPM. Also wouldn't be consistent with " It does it mostly when I have been driving a while."

Doesn't sound like the AIR pump to me, or else the description included in the first post is not very accurate. If the engine had been running for more than 5 minutes (an not restarted just before the mechanic listend to it) the AIR pump should not have been running.

 

Just wanted to give an update to this....

Injuneer,you were correct. It was not the smog pump.
I had already replaced it though, I have a buddy who works in a Chevy parts dept and he got me a discount on a new one, so no big deal. The parts store did not have the correct once since mine had the pigtail on it.

Anyways,today it started to squeal like a banshee on the way back from a 50 mile drive. I get home,pop the hood and start to listen to try and fine this horrible noise. I notice that it seems to be coming from around the throttle body.I turn off the car. I see a rubber hose attached underneath the TB that's attached to a metal line that goes to the PCV valve. Now I grab that rubber hose and it is like putty in my hands,there was no resistance to me mashing it at all. I start the car and the noise is there,I then move that rubber hose around and the noise stops,I move it more and I can make it louder or completely quiet.BINGO!

I assume that it was getting sucked shut from the vacuum put on it.

 

I like happy endings

 

Just got through driving around a good 15-20 miles and NO noise.