just bought a 1999 chevy blazer with 52000 miles. when i start it there is a whistling noise coming from i think under the engine. wondering what it could be. goes away after 30 seconds or so. any help is greatly appreciated.

 

Under? what year, model.... motor? the onlly thing i can think of is what i had on another vehicle. when i would start it up and get a whistle for like a minute... it turned out to be the altinator... the pully on it.

 

You'll definitely want to check your belts. If you can't remember when the last time your accessory drive belt was changed, just change it and keep the other one for a spare (I carry a spare with me in all of my vehicles - you never know when you could use it!). While/if you have the belt off, rotate the alternator by hand to see if there are any rough spots. As Dory stated, it could be the alternator starting to go (dry bearing) and after it spins for a bit, it may quiet down (for now) because of the heat buildup in the bearing. That won't last though and you should be able to feel some stickyness (is that a word - lol) in the alternator when rotated by hand.

Now another explaination is the positioning of the IAC valve and how it is used to control the idle speed of your truck. The IAC (idle air control) valve is located in the throttle body. It is a simple pintle valve arrangement and on certain vehicles, it can cause a whistling sound on cold startups if the passage gets dirty. If this is what it turns out to be, a simple cleaning of the throttle body (requires removal of the TB), may correct the annoyance.

Good Luck!

 

thanks i will check on those things today