Buzzing Noise From Intake Manifold

[Meh987]

I went to the track yesterday. After one of my first few runs, when slowing down, I heard a wierd buzzing noise coming from my engine. I checked and it seems to be coming from or under the intake manifold. I don't ususally hear it when I'm driving. Ususally I will hear it when letting off the throttle or at idle. It hasn't affected the performance of the car, just an annoying sound. So does anyone know what's wrong?

 

[Meh987]

I have just noticed that the sound speeds up when the engine revs up. The best way to describe the sound would be like something rubbing against a belt. Also, if you push down on the intake manifold, the sound goes away.

 

[MrPikolo]

I am also curios to what is making this noise and if anyone else has had a simular experince.

 

[TurboAWDjunkie]

you might have a vacuum leak .. i ended up changing the intake manifold gasket .. but on the other hand it woud effect the performance of your car .... do you have idle surge ? if you its most likely that u have a vacuum leak

 

[Meh987]

Nope, no idle surge. I'll check for any vacuum leaks in the morning. Do you think theres anyway it could be transmission-related? It's now only happening when I go in reverse, or when I let off the throttle while I'm in gear.

 

[my95tsi]

well if you had a vacuum leak you can tell just ny looking at your boost gauge...

 

[Meh987]

I finally figured out the problem. I noticed that my A/C belt had split in half and was lightly shredded. So, I took the A/C belt off, and the sound was gone. It turns out there was a plastic shield that had been pushed up towards the A/C compressor, really close to where the belt was. The belt had been rubbing against that plastic and making the noise. I pryed it out the way, put a new belt on, and the sound was gone.