Pulley? Violently Shaking?
 

I'll have a video up soon, but I was looking at my engine bay today with the car on, and the second pulley? (Not too sure what it is, I'm a noob at this stuff.) Around the belt was shaking side to side pretty violently it looked. Is this normal on these cars? Here's a picture of an engine bay I found online, I circled the problematic one.

The other two are working fine, but this one looks like it's shaking side to side very fast.

http://imageshack.us/a/img823/9199/harlemshake.jpg

That appears to be the belt tensioner, is it supposed to vibrate a lot?

[ame="http://www.youtube.com/watch?v=ZJLgZkjbS8g"]FRS Belt Tensioner + Cricket Noise - YouTube[/ame]

Just searched and said it's normal? But, I'm still a little skeptical..any ideas? Just ran out and took a video after turning my car back on, wasn't really shaking at all. But I took a video anyway, and I believe the crickets started? I dunno, I think I'm being overly-cautious, but I can never be too sure with this car..

Is the car acting strange? Has something changed? Is there anything different now other than you noticed it? Without seeing a video, unless it's moving several inches each way I think you'll be okay.

That is normal although I agree a bit unnerving.

I'll try to take another video after I'm driving. It was shaking like a MOFO. But for some reason when I turned it back on, seemed to be fine.

Was it a cold start? Does it go away after engine is warmed up a bit?

100% normal :-)

Some parts are meant to flex, it allows for the forces to be distributed in such a way that the parts don't fail because the stresses are below the threshold that will cause permanent damage. If it seems to be consistent with what other people are seeing then it was built that way on purpose and only time will tell if it's a flaw.

Completely normal. That pulley is mounted to a spring-loaded belt tensioner that's designed to keep the overall tension of the belt at a set point. As the engine goes through its cycles, and the alternator adjusts for loads, and other things occur, loads on the belt can change so this pulley will bounce, even rapidly as you're seeing, to maintain the proper tension.

Automatic Belt Tensioners are used on MANY cars. It allows the engineers to design an accessory system that uses one LONG belt rather than multiple smaller ones. Otherwise you wouldn't be able to compensate for the changes in length and tension with such a long belt. It also reduces the time needed to change the belt since you can just swing the tensioner out of the way to remove the belt and put the new one on.

Thanks guys. :)

im having the same issue. is this normal then?

Yep 100% normal, basically it is just soaking up the tension the engine, A/C, and Alternator create on the belt. :)

Thanks,
Rick

what do you guys think of mine? listen past the crickets, past the exhaust and past the pulley. theres a weird sound and its got me concerned. it only happens when i turn the AC on.

[ame="http://www.youtube.com/watch?v=WjZHWAkhkFI&feature=c4-overview&list=UUL4djS2xrkT2ist4nlAvRMg"]Fa20 AC on - YouTube[/ame]

^ I hear the whistle.

That needs to be lubed.

The other clunking sounds wrong.

Crickets are DI so that's okay.

The other sound is like an echo between two metal pieces.

However if it occurs when AC is turned on it is the compressor.
And that's pretty loud for a compressor.

Normal.