Clanging sound from Belt area???

I have a 2000 Montana with 143,000 miles on it. For about the past 3 months it has had an intermittent metal clanging sound coming from the engine. It sounds a lot like a someone tapping on a pulley, but before I pull things apart i want to see if someone might know which one is suspect or if it might be something like the timing chain. One other thing that I've noticed is when I turn the AC on the noise goes away. When I turn the AC off, it comes back. any advice is appreciated.

I don't think your engine has a timing chain. You can take the serpentine belt off and see if any pulleys are loose. Also see if your idler itself is loose.

AC compressor air gap is too close, you have to use special tool for V5 compressor to adjust the gap.

this is your problem 100% I am GM master tech 14 years, and disregard this negative reputation, one of the moderators did not like my suggestion and gave me one negative point. Please give me thumbs up to fix this. Thank you 3100

this is the tool that you need: http://www.sjdiscounttools.com/kdt3340.html

it is also easy to do it you don't have to disconnect ac compressor lines, you have to remove two bolts on top and one on the bottom so that ac drops down this way you will have space to use this tool.

I will give it a try. is there a step by step guide that shows the work on the internet? I have never had an issue with it before, but I did add freon to the vehicle this summer. Could this be something that messed it up? I don't have a lot of experience with ac units on vehicles.