Whistling Noise @ Idle

peggydukes1 · March 17, 2009

I have a 08 GMC Sierra 1500 Truck (V8) now with 10,000 miles. I've taken my truck in four times to the dealership for this whistling noise. 1st time, they thought i was hearing things because i was a woman. 2nd time, they coudn't get it to make the noise. 3rd time I drove it straight to them, left the truck running in park so they could hear it for themselves. They replaced the tension and also put a new belt on. I drove straight home after 20 minutes, came to a stop, rolled down the window to say hi to the neighbor and there was the same noise. Next day, drove straight dealership, let the truck running in park again, so they could hear the noise. This time they said I had a mild build up of carbon on my throttle.(What?) Well guess what, came home, rolled window down in my driveway and the noise is still there but now it's getting louder. It does not make the sound @ start up. I only notice when its been driven for about 20 minutes. (About the time to work or from work)

Do you have any suggestions as to why this is happening because the guys at this dealership obviously have no clue!

DofD · March 17, 2009

Hey there and welcome to GM Trucks!

Does the sound change pitch with changes in the RPMs?

Hard to say without hearing it. But since a whistling noise is generally related to the movement of air through a small space. Since it only happens when the truck is warm, so something is getting, warm, expanding, and letting air pass that it shouldn't. My bet would be that you have a vacuum leak. Possibly as the truck gets warm a vacuum hose isn't fitting snugly or a clamp isn't tight enough.