Noise at startup.. PLease help!!!!

I have a Chevy Trailblazer that makes an awful "winding: noise when you start it up. Now it will do this in several occasions..

1- Startup after engine is cooled down
2- Sometimes during driving I can hear it spin for just a moment
3- If engine is somewhat warm it will only do it for a moment

I have checked under the hood and cant see anything that is making the noise... Sounds like it may be coming from under the engine. I have a video link here... Please help me... It wakes my neighbors every morning I go to work

http://youtu.be/BxPMBucRbYK

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so sitting in park cold you can hear the whine thats the way i am reading this. if so it sounds like a bearing on one of the drive belt pulleys such as tensioner or idler pulley, a/c or alt pulley etc...

so sitting in park cold you can hear the whine thats the way i am reading this. if so it sounds like a bearing on one of the drive belt pulleys such as tensioner or idler pulley, a/c or alt pulley etc...

I'll back out- you go ahead and help him locate & replace

you said you heard a winding noise you will have to be more clear on the noise, is it more like a whistle,squel,winding noise tells me it sounds like the window is cracked and the wind wipping through the car but the sound is coming from under the engine if so you may have sucked the air cleaner to hard on excelaration and the filter may not be seated correctly which could cause this noise a bearing would make like a squeling noise and if it is another accesory you could carefully take a long screwdriver like at least 12" or longer and while the engine is at idle touch the screwdriver to the different accessories near the pullies and put your ear to the handle if you find the bad bearing the squel will get significantly louder but do this veery carefully you do not want to get anything caught in the drive belt while the engine is running. if it is a wind whistleing noise maybe you have a vacume leak or even an exhaust leak veery small sometimes mufflers have a weep hole in the bottom rear of the muffler so condinsation can leak out i have seen the exhaust come through this hole and make noise like you are discribing but that would not be under the engine , you have a couple of things to check if you need to comment back i will check back later, good luck!

I certainly agree with listening with something physically contacting the various areas supporting moving parts. My favorite 'tool' is a wooden dowel rod about 2 ft or 3 ft long (I have one of each). One end is held against the bearing housing, or the center bolt on an idler pulley, or the water pump casting, etc. The other end I push my ear against, the little flap of skin that 'closes' the ear.
Auto parts stores also sell mechanics 'stethoscopes' that work pretty well.

Even if its not making the squeal at the time you are listening with the stick or stethoscope, you may hear an area that is harshly noisy that might be the problem waiting to happen.

Where is the alternator located on your vehicle? The front bearing on an alternator can make a periodic noise - and eventually can sieze up, usually in a non-convenient locale.