99 Astro Whistles when i accelerate

I just bought an Astro like 5 days ago for work and now its making a whistling noise when i accelerate. It goes away almost immediately but i dont know what it is and dont know much about cars. Can someone tell me what it could be.

Welcome to the forum!

Noises can be difficult to identify, and to pinpoint their origin. Where does it sound like it's coming from? A worn serpentine belt tensioner allowing the belt to slip can cause a whistle or squeal noise... something to check.

I did pop the hood yet and check but it does sound like its coming from under there somewhere....im so stupid when i comes to cars. Could it possibily be a vacuum leak? A few people said the the whistling noice shouldnt really cause any problems its just more annoying than anything...would you agree?

A vacuum leak could cause a whistle noise. If it is a vacuum leak causing the noise, it would be best to have it repaired as soon as possible. Vacuum leaks will cause a decrease in fuel mileage, and possibly damage the engine by injesting dirt. A vacuum leak will also cause the engine to run lean, which over time can damage the engine.

What all could it be? If it is the serp belt is that hard to replace?

Depends what the problem is. Replacing the serp belt and/or tensioner involves removing the air inlet system, (air filter housing etc) and upper fan shroud, (7 bolts) for easy access to the tensioner.

Ok so hopefully its not something thats really expensive and easy to fix

Hmm thats weird...i havent been driving my van cause it was whistling and when i started it up today to let a friend hear the noise, it wasnt whistling anymore hmmm...but it did kinda sound like air was bein pushed out somewhere underneath the hood so maybe it is a vacuum leak somewhere

Had a similar noise after I had the Serpentine belt replaced. Figured it was inherent in the belt. Sound slowly disappeared over time, like 2 years as the belt wore in. Hope that helps.

sounds like your catalytic converter needs to be replaced if your hearing a rushing whistling sound, if so your losing gas milage and power, and if its a 99 and more than likely never been replaced, then you've got nothing to lose.

is that expensive?

4 to 5 hundred;