I have a rattle at idle. It increases between 1000 and 2000 RPMs then goes away. The belt tensioner moves up and down slightly but doesn't look to be vibrating. It jerks a when the fan comes on then quits. When i place a long screwdriver against it it seems to be vibrating but hard to tell what is normal.

How can I test this and other pulleys?
Can I replace the belt first then the tensioner if it still rattles?
Or is it best to replace both?

I would hate to replace 1 or the other and it end up being something else. I can upload a video somewhere but my camera wouldn't focus right. Sound is still good though.

 

likely a pulley on the tensioner has failed if there's some noise.

Take off the belt and try moving the pulley by hand to rule that out.

 

I did that and it was loose so I replaced both belt and tensioner. It is alot quieter but it is still present. I took it to my mechanic and he believes it is near the water pump area. He just did a timing belt and pump job so if that's the issue he will take care of it no charge... Hope that's it.

 

did he replace the TB tensioner when he did the job?

 

No. I did yesterday myself. He worked on it 6 months ago, around 8000 miles. the rattle started about 3 weeks ago.

 

^^

Sorry thought you meant my drive belt. I believe he did. He is one to replace belt with new tensioner or tentioner with new belt.